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diff --git a/.gitignore b/.gitignore
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+a.out
+libft.a
+*.o
+*h.gch
+*swp
diff --git a/COPYING b/COPYING
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--- /dev/null
+++ b/COPYING
@@ -0,0 +1,674 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
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+                            Preamble
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+OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
+THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
+IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
+ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
+
+  16. Limitation of Liability.
+
+  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
+THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
+GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
+USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
+DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
+PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
+EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGES.
+
+  17. Interpretation of Sections 15 and 16.
+
+  If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If the program does terminal interaction, make it output a short
+notice like this when it starts in an interactive mode:
+
+    <program>  Copyright (C) <year>  <name of author>
+    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, your program's commands
+might be different; for a GUI interface, you would use an "about box".
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU GPL, see
+<https://www.gnu.org/licenses/>.
+
+  The GNU General Public License does not permit incorporating your program
+into proprietary programs.  If your program is a subroutine library, you
+may consider it more useful to permit linking proprietary applications with
+the library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.  But first, please read
+<https://www.gnu.org/licenses/why-not-lgpl.html>.
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..936b339
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,82 @@
+# Libft Copyright (C) 2026 yctct
+# 
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+CC = cc
+CFLAGS = -Wall -Werror -Wextra -g
+SRCS = ft_atoi.c \
+ft_bzero.c \
+ft_calloc.c \
+ft_isalnum.c \
+ft_isalpha.c \
+ft_isascii.c \
+ft_isdigit.c \
+ft_isprint.c \
+ft_itoa.c \
+ft_memchr.c \
+ft_memcmp.c \
+ft_memcpy.c \
+ft_memmove.c \
+ft_memset.c \
+ft_putchar_fd.c \
+ft_putchar.c \
+ft_putstr_fd.c \
+ft_putstr.c \
+ft_putendl_fd.c \
+ft_putnbr_fd.c \
+ft_putnbr.c \
+ft_split.c \
+ft_strchr.c \
+ft_strdup.c \
+ft_striteri.c \
+ft_strlcat.c \
+ft_strlcpy.c \
+ft_strlen.c \
+ft_strjoin.c \
+ft_strmapi.c \
+ft_strncmp.c \
+ft_strnstr.c \
+ft_strrchr.c \
+ft_strtrim.c \
+ft_substr.c \
+ft_tolower.c \
+ft_toupper.c \
+ft_lstnew.c \
+ft_lstadd_front.c \
+ft_lstsize.c \
+ft_lstlast.c \
+ft_lstadd_back.c \
+ft_lstdelone.c \
+ft_lstclear.c \
+ft_lstiter.c \
+ft_lstmap.c
+
+OBJS = $(SRCS:.c=.o)
+NAME = libft.a
+DEPS = libft.h
+
+%.o: %.c $(DEPS)
+	$(CC) -c -o $@ $< $(CFLAGS)
+
+$(NAME): $(OBJS)
+	ar rcs $(NAME) $(OBJS)
+
+all: $(NAME)
+
+.PHONY: clean fclean re
+clean:
+	rm -f *.o
+fclean: clean
+	rm -f $(NAME)
+re: fclean all
diff --git a/README b/README
new file mode 100644
index 0000000..3140f92
--- /dev/null
+++ b/README
@@ -0,0 +1,242 @@
+Libft 
+====
+
+Description 
+----------
+
+This repository carries selected functions replicated from The GNU C Library,
+`glibc` , additional functions that are not included in `glibc` as well as
+functions dealing with linked lists.
+
+Scroll down for a list and description of each of the functions.
+
+The motivation for writing this library is to learn C, and to have a set of
+functions I will use for future C projects.
+
+Instructions
+------------
+
+To clone this repository of this library run:
+
+	$ git clone https:/git.yctct.com/libft libft $ cd libft
+
+To compile the library run:
+
+	$ make
+
+To recompile the library run:
+
+	$ make re
+
+To delete all object files run:
+
+	$ make clean
+
+To delete all object files and libft.a run:
+
+	$ make fclean
+
+Add #include "path/to/libft.h" at the top of your \*.c files.
+
+Resources
+--------
+
+- man pages: ascii, limits.h and all the man pages of functions that are
+  replicated in this library.
+
+On libraries: 
+
+- [C Libraries](https://www.cs.swarthmore.edu/~newhall/unixhelp/howto_C_libraries.html)
+
+On makefiles: 
+
+- [Makefiles](https://www.cs.dartmouth.edu/~cs50/Lectures/makefiles/) 
+- [A Simple Makefile Tutorial, Bruce A.
+  Maxwell](https://cs.colby.edu/maxwell/courses/tutorials/maketutor/)
+- the man pages of  `make` and `ar`
+
+On malloc: 
+
+- [Dynamic Memory
+  Allocation](https://www.cs.cornell.edu/courses/cs3410/2025fa/rsrc/c/malloc.html) 
+- [Malloc: Allocating Memory in C, Mia
+  Combeau](https://www.codequoi.com/en/malloc-allocating-memory-in-c/)
+
+On linked list and struct: 
+
+- [Beej's Guide to C programming, chapter 8, Struct, 2025 Brian “Beej
+  Jorgensen” Hall](https://beej.us/guide/bgc/html/#structs)
+- [Zeste de Savoir, Les
+  structures](https://zestedesavoir.com/tutoriels/755/le-langage-c-1/1043_aggregats-memoire-et-fichiers/4279_structures/#1-12828_definition-initialisation-et-utilisation)
+- Practical C, Steve Oualline, O'Reilly, 3rd edition
+
+On Markdown: 
+
+- [Markdown, John Gruber](https://daringfireball.net/projects/markdown/) which
+  as a script to convert Markdown to HTML
+
+
+Description of functions 
+-------------------------
+
+**Functions from `libc`**
+
+`libft.h`: contain all the prototypes, libraries needed and struct.
+
+`Makefile`: contain all the rules to compile, recomplie and clean.
+
+`ft_isalpha`: checks if all characters in a given string are is alphabetical.
+
+`ft_isdigit`: checks if all characters in a given string are digits.
+
+`ft_isalnum`: checks if all characters in a given string are alphabetical or
+digits .
+
+`ft_isascii`: checks if an integer is within the range of ascii value.
+
+`ft_isprint`: checks if an integer is within the range of printable ascii
+value.
+
+`ft_strlen`: calculates the length of a given string .
+
+`ft_memset`: fills the first n bytes of a memory area with a constant c.
+
+`ft_bzero`: fills the first n bytes of a memory area with '0'.
+
+`ft_memcpy`: copies n bytes from a memory area src to memory dest.
+
+`ft_memmove`: copies n bytes from a memory area src to memory dest, memory
+areas may overlap.
+
+`ft_strlcpy`: copies up to size - 1 characters from the NUL-terminated string
+src to dst, NUL-terminating the result.
+
+`ft_strlcat`: appends the NUL-terminated string src to the end of dst. It will
+append at most size - strlen(dst) - 1 bytes, NUL-terminating the result.
+
+`ft_toupper`: converts lowercase letters to uppercase.
+
+`ft_tolower`: converts uppercase letters to lowercase.
+
+`ft_strchr`: returns  a  pointer to the first occurrence of the character c in
+the string s.
+
+`ft_strrchr`: returns a pointer to the last occurrence of  the  character  c
+in  the string s.
+
+`ft_strncmp`: compares the first (at most) n bytes of strings s1 and s2.
+
+`ft_memchr`: scans  the initial n bytes of the memory area pointed to by s for
+the first instance of c.
+
+`ft_memcmp`: compares the first n bytes (each interpreted as unsigned char) of
+the memory areas s1 and s2.
+
+`ft_strnstr`: locates the first occurrence of the null-terminated string little
+in the string big, where not more than len characters are searched.
+
+`ft_atoi`: converts the initial portion of the string pointed to by nptr to
+int.
+
+`ft_calloc `: allocates memory for an array of nmemb elements of size bytes
+each and returns a pointer to the allocated memory.  The memory is set to zero.
+If nmemb or size is 0, then  calloc()  returns a unique pointer value that can
+later be successfully passed to free().  If the multiplication of nmemb and
+size would result in  integer  overflow, then calloc() returns an error.  
+
+`ft_strdup`: returns a pointer to a new string which is a duplicate of the
+string s.  Memory for the new string is obtained with malloc(3), and can be
+freed with free(3).
+
+**Additional functions**
+
+`ft_substr`: Allocates memory (using malloc(3)) and returns a substring from
+the string ’s’.  The substring starts at index ’start’ and has a maximum length
+of ’len’.
+
+`ft_strjoin`: Allocates memory (using malloc(3)) and returns a new string,
+which is the result of concatenating ’s1’ and ’s2’.
+
+`ft_strtrim`: Allocates memory (using malloc(3)) and returns a copy of ’s1’
+with characters from ’set’ removed from the beginning and the end.
+
+`ft_split`: Allocates memory (using malloc(3)) and returns an array of strings
+obtained by splitting ’s’ using the character ’c’ as a delimiter. The array
+must end with a NULL pointer.
+
+`ft_itoa`: Allocates memory (using malloc(3)) and returns a string representing
+the integer received as an argument. Negative numbers must be handled
+
+`ft_strmapi`: Applies the function f to each character of the string s, passing
+its index as the first argument and the character itself as the second. A new
+string is created (using malloc(3)) to store the results from the successive
+applications of f.
+
+`ft_striteri`: Applies the function ’f’ to each character of the string passed
+as argument, passing its index as the first argument. Each character is passed
+by address to ’f’ so it can be modified if necessary.
+
+`ft_putchar_fd`: Outputs the character ’c’ to the specified file descriptor. 
+
+`ft_putstr_fd`: Outputs the string ’s’ to the specified file descriptor. 
+
+`ft_putendl_fd`: Outputs the string ’s’ to the specified file descriptor
+followed by a new line.
+
+`ft_putnbr_fd`: Outputs the integer ’n’ to the specified file descriptor. 
+
+**Linked list functions**
+
+The following struct was added to `libf.h`:
+
+	typedef struct s_list 
+	{ 
+		void *content; 
+		struct s_list *next; 
+	} t_list;
+
+`ft_lstnew`: Allocates memory (using malloc(3)) and returns a new node. The
+’content’ member variable is initialised with the given parameter ’content’.
+The variable ’next’ is initialised to NULL.
+
+`ft_lstadd_front`: Adds the node ’new’ at the beginning of the list.
+
+`ft_lstsize`: Counts the number of nodes in the list.
+
+`ft_lstlast`: Returns the last node of the list.
+
+`ft_lstadd_back`: Adds the node ’new’ at the end of the list.
+
+`ft_lstdelone`: Takes a node as parameter and frees its content using the
+function ’del’. Free the node itself but does NOT free the next node.
+
+`ft_lstclear`: Deletes and frees the given node and all its successors, using
+the function ’del’ and free(3).  Finally, set the pointer to the list to NULL.
+
+`ft_lstiter`: Iterates through the list ’lst’ and applies the function ’f’ to
+the content of each node.
+
+`ft_lstmap`: Iterates through the list ’lst’, applies the function ’f’ to each
+node’s content, and creates a new list resulting of the successive applications
+of the function ’f’. The ’del’ function is used to delete the content of a node
+if needed.
+
+License
+-------
+
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+See the file COPYING.
diff --git a/ft_atoi.c b/ft_atoi.c
new file mode 100755
index 0000000..4633d2f
--- /dev/null
+++ b/ft_atoi.c
@@ -0,0 +1,94 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+int	ft_atoi(const char *nptr)
+{
+	int	i;
+	int	tmp;
+	int	nbl;
+
+	i = 0;
+	nbl = 0;
+	while (nptr[i] == 32 || (nptr[i] >= 7 && nptr[i] <= 13))
+		i++;
+	tmp = 1;
+	if (nptr[i] == '-')
+	{
+		i++;
+		tmp *= -1;
+	}
+	else if (nptr[i] == '+')
+		i++;
+	while (nptr[i] >= 48 && nptr[i] <= 57)
+	{
+		nbl = (nbl * 10) + nptr[i] - 48;
+		i++;
+	}
+	return (tmp * nbl);
+}
+
+/*
+#include <stdio.h>
+#include <stdlib.h>
+
+int	main(void)
+{
+	printf("for:          ---+--+1234ab567\n");
+	printf("ft_atoi: %i\n", ft_atoi("   --+--+1234ab567"));
+	printf("   atoi: %i\n", atoi("   ---+-+1234ab567"));
+	printf("------------------------------------\n");
+	printf("for:     3\n");
+	printf("ft_atoi: %i\n", ft_atoi("3"));
+	printf("   atoi: %i\n", atoi("3"));
+	printf("------------------------------------\n");
+	printf("for:     0\n");
+	printf("ft_atoi: %i\n", ft_atoi("0"));
+	printf("   atoi: %i\n", atoi("0"));
+	printf("------------------------------------\n");
+	printf("for:     -1\n");
+	printf("ft_atoi: %i\n", ft_atoi("-1"));
+	printf("   atoi: %i\n", atoi("-1"));
+	printf("------------------------------------\n");
+	printf("for:     2147483647\n");
+	printf("ft_atoi: %i\n", ft_atoi("2147483647"));
+	printf("   atoi: %i\n", atoi("2147483647"));
+	printf("------------------------------------\n");
+	printf("for:     -2147483648\n");
+	printf("ft_atoi: %i\n", ft_atoi("-2147483648"));
+	printf("   atoi: %i\n", atoi("-2147483648"));
+	printf("------------------------------------\n");
+	printf("for:     -2147483647\n");
+	printf("ft_atoi: %i\n", ft_atoi("-2147483647"));
+	printf("   atoi: %i\n", atoi("-2147483647"));
+	printf("------------------------------------\n");
+	printf("for:     2147483648\n");
+	printf("ft_atoi: %i\n", ft_atoi("2147483648"));
+	printf("   atoi: %i\n", atoi("2147483648"));
+	printf("------------------------------------\n");
+	printf("for:     -+27\n");
+	printf("ft_atoi: %i\n", ft_atoi("-+27"));
+	printf("   atoi: %i\n", atoi("-+27"));
+	printf("------------------------------------\n");
+	printf("for:     +27\n");
+	printf("ft_atoi: %i\n", ft_atoi("+27"));
+	printf("   atoi: %i\n", atoi("+27"));
+	printf("------------------------------------\n");
+	printf("for:     #27\n");
+	printf("ft_atoi: %i\n", ft_atoi("#27"));
+	printf("   atoi: %i\n", atoi("#27"));
+}
+*/
diff --git a/ft_bzero.c b/ft_bzero.c
new file mode 100644
index 0000000..1d5d849
--- /dev/null
+++ b/ft_bzero.c
@@ -0,0 +1,23 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+void	ft_bzero(void *s, size_t n)
+{
+	ft_memset(s, 0, n);
+}
diff --git a/ft_calloc.c b/ft_calloc.c
new file mode 100644
index 0000000..d52d340
--- /dev/null
+++ b/ft_calloc.c
@@ -0,0 +1,44 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+void	*ft_calloc(size_t nmemb, size_t size)
+{
+	void	*ptr;
+	size_t	totalsize;
+
+	totalsize = size * nmemb;
+	if (nmemb != 0 && totalsize / nmemb != size)
+		return (NULL);
+	if (totalsize == 0)
+		totalsize = 1;
+	ptr = malloc(totalsize);
+	if (!ptr)
+		return (NULL);
+	ft_bzero(ptr, totalsize);
+	return (ptr);
+}
+
+/*
+#include <stdio.h>
+
+int	main(void)
+{
+	printf("%p\n", ft_calloc(0, 0));
+}
+*/
diff --git a/ft_isalnum.c b/ft_isalnum.c
new file mode 100644
index 0000000..bd2a81d
--- /dev/null
+++ b/ft_isalnum.c
@@ -0,0 +1,86 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+int	ft_isalnum(int c)
+{
+	if (ft_isalpha(c) || ft_isdigit(c))
+		return (1);
+	return (0);
+}
+
+/*
+int	main(void)
+{
+	printf("       for: NULL (0)\n");
+	printf("ft_isalnum: %d\n", ft_isalnum(0));
+	printf("   isalnum: %d\n", isalnum(0));
+	printf("\n");
+	printf("       for: / (47)\n");
+	printf("ft_isalnum: %d\n", ft_isalnum(47));
+	printf("   isalnum: %d\n", isalnum(47));
+	printf("\n");
+	printf("       for: 0 (48)\n");
+	printf("ft_isalnum: %d\n", ft_isalnum(48));
+	printf("   isalnum: %d\n", isalnum(48));
+	printf("\n");
+	printf("       for: 9 (57)\n");
+	printf("ft_isalnum: %d\n", ft_isalnum(57));
+	printf("   isalnum: %d\n", isalnum(57));
+	printf("\n");
+	printf("       for: : (58)\n");
+	printf("ft_isalnum: %d\n", ft_isalnum(58));
+	printf("   isalnum: %d\n", isalnum(58));
+	printf("\n");
+	printf("       for: @ (64)\n");
+	printf("ft_isalnum: %d\n", ft_isalnum(64));
+	printf("   isalnum: %d\n", isalnum(64));
+	printf("\n");
+	printf("       for: A (65)\n");
+	printf("ft_isalnum: %d\n", ft_isalnum(65));
+	printf("   isalnum: %d\n", isalnum(65));
+	printf("\n");
+	printf("       for: Z (90)\n");
+	printf("ft_isalnum: %d\n", ft_isalnum(90));
+	printf("   isalnum: %d\n", isalnum(90));
+	printf("\n");
+	printf("       for: [ (91)\n");
+	printf("ft_isalnum: %d\n", ft_isalnum(91));
+	printf("   isalnum: %d\n", isalnum(91));
+	printf("\n");
+	printf("       for: ` (96)\n");
+	printf("ft_isalnum: %d\n", ft_isalnum(96));
+	printf("   isalnum: %d\n", isalnum(96));
+	printf("\n");
+	printf("       for: a (97)\n");
+	printf("ft_isalnum: %d\n", ft_isalnum(97));
+	printf("   isalnum: %d\n", isalnum(97));
+	printf("\n");
+	printf("       for: z (122)\n");
+	printf("ft_isalnum: %d\n", ft_isalnum(122));
+	printf("   isalnum: %d\n", isalnum(122));
+	printf("\n");
+	printf("       for: } (123)\n");
+	printf("ft_isalnum: %d\n", ft_isalnum(123));
+	printf("   isalnum: %d\n", isalnum(123));
+	printf("\n");
+	printf("       for: DEL (127)\n");
+	printf("ft_isalnum: %d\n", ft_isalnum(127));
+	printf("   isalnum: %d\n", isalnum(127));
+}
+*/
diff --git a/ft_isalpha.c b/ft_isalpha.c
new file mode 100644
index 0000000..14209d4
--- /dev/null
+++ b/ft_isalpha.c
@@ -0,0 +1,56 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+int	ft_isalpha(int c)
+{
+	if ((c >= 65 && c <= 90) || (c >= 97 && c <= 122))
+		return (1);
+	return (0);
+}
+/*
+int	main(void)
+{
+	printf("ft_isalpha: %d, %d\n", ft_isalpha(0), 0);
+	printf("   isalpha: %d, %d\n", isalpha(0), 0);
+	printf("\n");
+	printf("ft_isalpha: %d, %d\n", ft_isalpha(64), 64);
+	printf("   isalpha: %d, %d\n", isalpha(64), 64);
+	printf("\n");
+	printf("ft_isalpha: %d, %d\n", ft_isalpha(65), 65);
+	printf("   isalpha: %d, %d\n", isalpha(65), 65);
+	printf("\n");
+	printf("ft_isalpha: %d, %d\n", ft_isalpha(90), 90);
+	printf("   isalpha: %d, %d\n", isalpha(90), 90);
+	printf("\n");
+	printf("ft_isalpha: %d, %d\n", ft_isalpha(91), 91);
+	printf("   isalpha: %d, %d\n", isalpha(91), 91);
+	printf("\n");
+	printf("ft_isalpha: %d, %d\n", ft_isalpha(96), 96);
+	printf("   isalpha: %d, %d\n", isalpha(96), 96);
+	printf("\n");
+	printf("ft_isalpha: %d, %d\n", ft_isalpha(97), 97);
+	printf("   isalpha: %d, %d\n", isalpha(97), 97);
+	printf("\n");
+	printf("ft_isalpha: %d, %d\n", ft_isalpha(122), 122);
+	printf("   isalpha: %d, %d\n", isalpha(122), 122);
+	printf("\n");
+	printf("ft_isalpha: %d, %d\n", ft_isalpha(123), 123);
+	printf("   isalpha: %d, %d\n", isalpha(123), 123);
+}
+*/
diff --git a/ft_isascii.c b/ft_isascii.c
new file mode 100644
index 0000000..0c05a32
--- /dev/null
+++ b/ft_isascii.c
@@ -0,0 +1,54 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+int	ft_isascii(int c)
+{
+	if ((c >= 0) && (c <= 127))
+		return (1);
+	return (0);
+}
+
+/*
+int	main(void)
+{
+	printf("       for:    (-10)\n");
+	printf("ft_isascii: %d\n", ft_isascii(-10));
+	printf("   isascii: %d\n", isascii(-10));
+	printf("\n");
+	printf("       for: NULL (0)\n");
+	printf("ft_isascii: %d\n", ft_isascii(0));
+	printf("   isascii: %d\n", isascii(0));
+	printf("\n");
+	printf("       for: / (47)\n");
+	printf("ft_isascii: %d\n", ft_isascii(47));
+	printf("   isascii: %d\n", isascii(47));
+	printf("\n");
+	printf("       for: } (123)\n");
+	printf("ft_isascii: %d\n", ft_isascii(123));
+	printf("   isascii: %d\n", isascii(123));
+	printf("\n");
+	printf("       for: DEL (127)\n");
+	printf("ft_isascii: %d\n", ft_isascii(127));
+	printf("   isascii: %d\n", isascii(127));
+	printf("\n");
+	printf("       for:    (128)\n");
+	printf("ft_isascii: %d\n", ft_isascii(128));
+	printf("   isascii: %d\n", isascii(128));
+}
+*/
diff --git a/ft_isdigit.c b/ft_isdigit.c
new file mode 100644
index 0000000..a41b0e5
--- /dev/null
+++ b/ft_isdigit.c
@@ -0,0 +1,47 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+int	ft_isdigit(int c)
+{
+	if (c >= 48 && c <= 57)
+		return (1);
+	return (0);
+}
+/*
+int	main(void)
+{
+	printf("ft_isdigit: %d, %d\n", ft_isdigit(0), 0);
+	printf("   isdigit: %d, %d\n", isdigit(0), 0);
+	printf("\n");
+	printf("ft_isdigit: %d, %d\n", ft_isdigit(47), 47);
+	printf("   isdigit: %d, %d\n", isdigit(47), 47);
+	printf("\n");
+	printf("ft_isdigit: %d, %d\n", ft_isdigit(48), 48);
+	printf("   isdigit: %d, %d\n", isdigit(48), 48);
+	printf("\n");
+	printf("ft_isdigit: %d, %d\n", ft_isdigit(57), 57);
+	printf("   isdigit: %d, %d\n", isdigit(57), 57);
+	printf("\n");
+	printf("ft_isdigit: %d, %d\n", ft_isdigit(58), 58);
+	printf("   isdigit: %d, %d\n", isdigit(58), 58);
+	printf("\n");
+	printf("ft_isdigit: %d, %d\n", ft_isdigit(127), 127);
+	printf("   isdigit: %d, %d\n", isdigit(127), 127);
+}
+*/
diff --git a/ft_isprint.c b/ft_isprint.c
new file mode 100644
index 0000000..150d609
--- /dev/null
+++ b/ft_isprint.c
@@ -0,0 +1,90 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+int	ft_isprint(int c)
+{
+	if ((c >= 32) && (c <= 126))
+		return (1);
+	return (0);
+}
+
+/*
+int	main(void)
+{
+	printf("       for: NULL (0)\n");
+	printf("ft_isprint: %d\n", ft_isprint(0));
+	printf("   isprint: %d\n", isprint(0));
+	printf("\n");
+	printf("       for: unit separator (31)\n");
+	printf("ft_isprint: %d\n", ft_isprint(31));
+	printf("   isprint: %d\n", isprint(31));
+	printf("\n");
+	printf("       for: / (47)\n");
+	printf("ft_isprint: %d\n", ft_isprint(47));
+	printf("   isprint: %d\n", isprint(47));
+	printf("\n");
+	printf("       for: 0 (48)\n");
+	printf("ft_isprint: %d\n", ft_isprint(48));
+	printf("   isprint: %d\n", isprint(48));
+	printf("\n");
+	printf("       for: 9 (57)\n");
+	printf("ft_isprint: %d\n", ft_isprint(57));
+	printf("   isprint: %d\n", isprint(57));
+	printf("\n");
+	printf("       for: : (58)\n");
+	printf("ft_isprint: %d\n", ft_isprint(58));
+	printf("   isprint: %d\n", isprint(58));
+	printf("\n");
+	printf("       for: @ (64)\n");
+	printf("ft_isprint: %d\n", ft_isprint(64));
+	printf("   isprint: %d\n", isprint(64));
+	printf("\n");
+	printf("       for: A (65)\n");
+	printf("ft_isprint: %d\n", ft_isprint(65));
+	printf("   isprint: %d\n", isprint(65));
+	printf("\n");
+	printf("       for: Z (90)\n");
+	printf("ft_isprint: %d\n", ft_isprint(90));
+	printf("   isprint: %d\n", isprint(90));
+	printf("\n");
+	printf("       for: [ (91)\n");
+	printf("ft_isprint: %d\n", ft_isprint(91));
+	printf("   isprint: %d\n", isprint(91));
+	printf("\n");
+	printf("       for: ` (96)\n");
+	printf("ft_isprint: %d\n", ft_isprint(96));
+	printf("   isprint: %d\n", isprint(96));
+	printf("\n");
+	printf("       for: a (97)\n");
+	printf("ft_isprint: %d\n", ft_isprint(97));
+	printf("   isprint: %d\n", isprint(97));
+	printf("\n");
+	printf("       for: z (122)\n");
+	printf("ft_isprint: %d\n", ft_isprint(122));
+	printf("   isprint: %d\n", isprint(122));
+	printf("\n");
+	printf("       for: } (123)\n");
+	printf("ft_isprint: %d\n", ft_isprint(123));
+	printf("   isprint: %d\n", isprint(123));
+	printf("\n");
+	printf("       for: DEL (127)\n");
+	printf("ft_isprint: %d\n", ft_isprint(127));
+	printf("   isprint: %d\n", isprint(127));
+}
+*/
diff --git a/ft_itoa.c b/ft_itoa.c
new file mode 100644
index 0000000..f892fb1
--- /dev/null
+++ b/ft_itoa.c
@@ -0,0 +1,113 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+static long int	ft_nbrlen(long int n)
+{
+	int	len;
+
+	len = 0;
+	if (n < 0)
+	{
+		n = -n;
+		len += 1;
+	}
+	while (n)
+	{
+		n /= 10;
+		len++;
+	}
+	return (len);
+}
+
+char	*ft_itoa(int nb)
+{
+	char	*c;
+	int		len;
+	long	n;
+
+	n = nb;
+	if (n == 0)
+		return (ft_strdup("0"));
+	len = ft_nbrlen(n);
+	c = malloc(sizeof(char) * (len + 1));
+	if (!c)
+		return (NULL);
+	if (n < 0)
+	{
+		n = -n;
+		c[0] = '-';
+	}
+	c[len] = '\0';
+	while (n)
+	{
+		c[--len] = (n % 10) + '0';
+		n /= 10;
+	}
+	return (c);
+}
+/*
+#include <stdio.h>
+#include <stdlib.h>
+
+int	main(void)
+{
+	int		n1;
+	int		n2;
+	int		n3;
+	int		n4;
+	int		n5;
+	char	*ptr;
+	char	*ptr2;
+	char	*ptr3;
+	char	*ptr4;
+	char	*ptr5;
+	char	*ptr6;
+	char	c;
+
+	c = 'a';
+	n1 = 42;
+	n2 = 0;
+	n3 = -42;
+	n4 = 2147483647;
+	n5 = -2147483648;
+	ptr = ft_itoa(n1);
+	printf("      42: %s\n", ptr);
+	free(ptr);
+	printf("----------------\n");
+	ptr2 = ft_itoa(n2);
+	printf("       0: %s\n", ptr2);
+	free(ptr2);
+	printf("----------------\n");
+	ptr3 = ft_itoa(n3);
+	printf("     -42: %s\n", ptr3);
+	free(ptr3);
+	printf("----------------\n");
+	ptr4 = ft_itoa(n4);
+	printf(" INT_MAX: %s\n", ptr4);
+	free(ptr4);
+	printf("----------------\n");
+	ptr5 = ft_itoa(n5);
+	printf(" INT_MIN: %s\n", ptr5);
+	free(ptr5);
+	printf("----------------\n");
+	ptr6 = ft_itoa(c);
+	printf("char 'a': %s\n", ptr6);
+	free(ptr6);
+}
+*/
diff --git a/ft_lstadd_back.c b/ft_lstadd_back.c
new file mode 100644
index 0000000..af9ad6b
--- /dev/null
+++ b/ft_lstadd_back.c
@@ -0,0 +1,33 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+void	ft_lstadd_back(t_list **lst, t_list *new)
+{
+	t_list	*last;
+
+	if (!new || !lst)
+		return ;
+	if (!(*lst))
+		*lst = new;
+	else
+	{
+		last = ft_lstlast(*lst);
+		last->next = new;
+	}
+}
diff --git a/ft_lstadd_front.c b/ft_lstadd_front.c
new file mode 100644
index 0000000..e406ba2
--- /dev/null
+++ b/ft_lstadd_front.c
@@ -0,0 +1,26 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+void	ft_lstadd_front(t_list **lst, t_list *new)
+{
+	if (!lst || !new)
+		return ;
+	new->next = *lst;
+	*lst = new;
+}
diff --git a/ft_lstclear.c b/ft_lstclear.c
new file mode 100644
index 0000000..e12d120
--- /dev/null
+++ b/ft_lstclear.c
@@ -0,0 +1,56 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+void	ft_lstclear(t_list **lst, void (*del)(void *))
+{
+	t_list	*current;
+	t_list	*tmp;
+
+	if (!lst || !del)
+		return ;
+	if (!(*lst))
+		return ;
+	current = *lst;
+	while (current->next)
+	{
+		tmp = current->next;
+		ft_lstdelone(current, del);
+		current = tmp;
+	}
+	ft_lstdelone(current, del);
+	*lst = NULL;
+}
+
+/*
+void	ft_lstclear(t_list **lst, void (*del)(void *))
+{
+	t_list	*tmp;
+
+	if (!lst)
+		return ;
+	if (!(*lst))
+		return ;
+	while (*lst)
+	{
+		tmp = (*lst)->next;
+		ft_lstdelone(*lst, del);
+		(*lst) = tmp;
+	}
+}
+*/
diff --git a/ft_lstdelone.c b/ft_lstdelone.c
new file mode 100644
index 0000000..a7450d5
--- /dev/null
+++ b/ft_lstdelone.c
@@ -0,0 +1,26 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+void	ft_lstdelone(t_list *lst, void (*del)(void *))
+{
+	if (!lst)
+		return ;
+	(*del)(lst->content);
+	free(lst);
+}
diff --git a/ft_lstiter.c b/ft_lstiter.c
new file mode 100644
index 0000000..85c404a
--- /dev/null
+++ b/ft_lstiter.c
@@ -0,0 +1,40 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+void	ft_lstiter(t_list *lst, void (*f)(void *))
+{
+	while (lst)
+	{
+		f(lst->content);
+		lst = lst->next;
+	}
+}
+
+/*
+{
+	t_list	*current;
+
+	current = lst;
+	while (current)
+	{
+		f(current->content);
+		current = current->next;
+	}
+}
+*/
diff --git a/ft_lstlast.c b/ft_lstlast.c
new file mode 100644
index 0000000..b8d7f88
--- /dev/null
+++ b/ft_lstlast.c
@@ -0,0 +1,30 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+t_list	*ft_lstlast(t_list *lst)
+{
+	t_list	*current;
+
+	if (!lst)
+		return (NULL);
+	current = lst;
+	while (current->next)
+		current = current->next;
+	return (current);
+}
diff --git a/ft_lstmap.c b/ft_lstmap.c
new file mode 100644
index 0000000..ed5e7c3
--- /dev/null
+++ b/ft_lstmap.c
@@ -0,0 +1,41 @@
+
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+t_list	*ft_lstmap(t_list *lst, void *(*f)(void *), void (*del)(void *))
+{
+	t_list	*newlist;
+	t_list	*newnode;
+
+	if (!lst || !f || !del)
+		return (NULL);
+	newlist = NULL;
+	while (lst)
+	{
+		newnode = ft_lstnew((*f)(lst->content));
+		if (!newnode)
+		{
+			ft_lstclear(&newlist, del);
+			return (NULL);
+		}
+		ft_lstadd_back(&newlist, newnode);
+		lst = lst->next;
+	}
+	return (newlist);
+}
diff --git a/ft_lstnew.c b/ft_lstnew.c
new file mode 100644
index 0000000..88194ed
--- /dev/null
+++ b/ft_lstnew.c
@@ -0,0 +1,59 @@
+
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+/* "If you want to put data in a heap structure pointed to by a structure
+pointer variable, you must use the structure pointer operator, ->."
+CP:ABG, p. 262
+
+t_list is an alias we defined with typedef so we don't need to prepend
+it with struct or use struct t-list
+
+'content' is both, the name of the variable/member defined in the struct and
+the name of the parameter  passed in the following function.
+E.g. in 'newnode-> content = content' the first one is the variable, defined
+in the struct, the second one is the parameter.
+*/
+
+#include "libft.h"
+
+t_list	*ft_lstnew(void *content)
+{
+	t_list	*newnode;
+
+	newnode = malloc(sizeof(t_list));
+	if (!newnode)
+		return (NULL);
+	newnode->content = content;
+	newnode->next = NULL;
+	return (newnode);
+}
+
+/*
+#include <stdio.h>
+
+int	main(void)
+{
+	t_list	*x;
+
+	x = ft_lstnew("hello");
+	printf("%s\n", (char*)(x-> content));
+	printf("0.6%s\n", (char*)(x-> next));
+	free(x);
+	return (0);
+}
+*/
diff --git a/ft_lstsize.c b/ft_lstsize.c
new file mode 100644
index 0000000..da7502f
--- /dev/null
+++ b/ft_lstsize.c
@@ -0,0 +1,31 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+int	ft_lstsize(t_list *lst)
+{
+	int	count;
+
+	count = 0;
+	while (lst)
+	{
+		count++;
+		lst = lst->next;
+	}
+	return (count);
+}
diff --git a/ft_memchr.c b/ft_memchr.c
new file mode 100644
index 0000000..bee5430
--- /dev/null
+++ b/ft_memchr.c
@@ -0,0 +1,34 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+void	*ft_memchr(const void *s, int c, size_t n)
+{
+	const char	*ss;
+	size_t		i;
+
+	ss = s;
+	i = 0;
+	while (i < n)
+	{
+		if (ss[i] == (char)c)
+			return ((void *)(ss + i));
+		i++;
+	}
+	return (NULL);
+}
diff --git a/ft_memcmp.c b/ft_memcmp.c
new file mode 100644
index 0000000..32f8eec
--- /dev/null
+++ b/ft_memcmp.c
@@ -0,0 +1,122 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+int	ft_memcmp(const void *s1, const void *s2, size_t n)
+{
+	unsigned char	*cs1;
+	unsigned char	*cs2;
+	size_t			i;
+
+	cs1 = (unsigned char *)s1;
+	cs2 = (unsigned char *)s2;
+	i = 0;
+	if (n == 0)
+		return (0);
+	while (i < n - 1 && cs1[i] == cs2[i])
+		i++;
+	return (cs1[i] - cs2[i]);
+}
+
+/*
+#include <string.h>
+
+int	main(void)
+{
+	char	s[] = {-128, 0, 127, 0};
+	char	sCpy[] = {-128, 0, 127, 0};
+
+	printf("%i\n", ft_memcmp(s, sCpy, 4));
+	printf("%i\n", memcmp(s, sCpy, 4));
+	printf("%i\n", ft_memcmp("abcdefghij", "abcdefgxyz", 7));
+	printf("%i\n", memcmp("abcdefghij", "abcdefgxyz", 7));
+}
+int	ft_memcmp(const void *s1, const void *s2, size_t n)
+{
+	size_t			i;
+	unsigned char	*a;
+	unsigned char	*b;
+
+	i = 0;
+	a = (unsigned char *)s1;
+	b = (unsigned char *)s2;
+	if (s1 == s2 || n == 0)
+		return (0);
+	while (*a == *b && i < n - 1)
+	{
+		a++;
+		b++;
+		i++;
+	}
+	return (*a - *b);
+}
+*/
+/*
+int	main(void)
+{
+			char s[] = {-128, 0, 127, 0};
+			char sCpy[] = {-128, 0, 127, 0};
+			char s2[] = {0, 0, 127, 0};
+			char s3[] = {0, 0, 42, 0};
+
+	printf("\n");
+			printf("%i\n", ft_memcmp(s, sCpy, 4));
+			printf("%i\n", memcmp(s, sCpy, 4));
+	printf("\n");
+			printf("%i\n", ft_memcmp(s, s2, 0));
+			printf("%i\n", memcmp(s, s2, 0));
+	printf("\n");
+			printf("%i\n", ft_memcmp(s, s2, 1));
+			printf("%i\n", memcmp(s, s2, 1));
+	printf("\n");
+			printf("%i\n", ft_memcmp(s2, s, 1));
+			printf("%i\n", memcmp(s2, s, 1));
+	printf("\n");
+			printf("%i\n", ft_memcmp(s2, s3, 4));
+			printf("%i\n", memcmp(s2, s3, 4));
+	printf("\n");
+	printf("\n");
+	printf("%i\n", ft_memcmp("salut", "salut", 5));
+	printf("%i\n", memcmp("salut", "salut", 5));
+	printf("\n");
+	printf("%i\n", ft_memcmp("t\200", "t\0", 2));
+	printf("%i\n", memcmp("t\200", "t\0", 2));
+	printf("\n");
+	printf("%i\n", ft_memcmp("testss", "test", 5));
+	printf("%i\n", memcmp("testss", "test", 5));
+	printf("\n");
+	printf("%i\n", ft_memcmp("test", "tEst", 4));
+	printf("%i\n", memcmp("test", "tEst", 4));
+	printf("\n");
+	printf("%i\n", ft_memcmp("", "test", 4));
+	printf("%i\n", memcmp("", "test", 4));
+	printf("\n");
+	printf("%i\n", ft_memcmp("test", "", 4));
+	printf("%i\n", memcmp("test", "", 4));
+	printf("\n");
+	printf("%i\n", ft_memcmp("abcdefghij", "abcdefgxyz", 7));
+	printf("%i\n", memcmp("abcdefghij", "abcdefgxyz", 7));
+	printf("\n");
+	printf("%i\n", ft_memcmp("abcdefgh", "abcdwxyz", 6));
+	printf("%i\n", memcmp("abcdefgh", "abcdwxyz", 6));
+	printf("\n");
+	printf("%i\n", ft_memcmp("zyxbcdefgh", "abcdefgxyz", 0));
+	printf("%i\n", memcmp("zyxbcdefgh", "abcdefgxyz", 0));
+			return (0);
+}
+*/
diff --git a/ft_memcpy.c b/ft_memcpy.c
new file mode 100644
index 0000000..1e75b3c
--- /dev/null
+++ b/ft_memcpy.c
@@ -0,0 +1,37 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+void	*ft_memcpy(void *dest, const void *src, size_t n)
+{
+	unsigned char	*a;
+	const char		*b;
+
+	if (n == 0)
+		return (dest);
+	if (!dest || !src)
+		return (dest);
+	a = dest;
+	b = src;
+	while (n > 0)
+	{
+		*a++ = *b++;
+		n--;
+	}
+	return (dest);
+}
diff --git a/ft_memmove.c b/ft_memmove.c
new file mode 100644
index 0000000..6264488
--- /dev/null
+++ b/ft_memmove.c
@@ -0,0 +1,54 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+void	*ft_memmove(void *dest, const void *src, size_t n)
+{
+	if (!dest && !src)
+		return (NULL);
+	if ((size_t)(dest - src) >= n)
+		return (ft_memcpy(dest, src, n));
+	else
+		while (n-- > 0)
+			((char *)dest)[n] = ((char *)src)[n];
+	return (dest);
+}
+/*
+int	main(void)
+{
+	int	i;
+
+	char	dest[]= "Hello,";
+	char	src[]= "world.";
+	char	dest2[]= "Hello,";
+	char	src2[]= "world.";
+	memmove((void *) dest, (void *)src, sizeof(src));
+	i = 0;
+	while (dest[i])
+	{
+		printf("%c", dest[i++]);
+	}
+	ft_memmove((void *) dest2, (void *)src2, sizeof(src2));
+	printf("\n");
+	i = 0;
+	while (dest2[i])
+	{
+		printf("%c", dest2[i++]);
+	}
+}
+*/
diff --git a/ft_memset.c b/ft_memset.c
new file mode 100644
index 0000000..300cac4
--- /dev/null
+++ b/ft_memset.c
@@ -0,0 +1,31 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+void	*ft_memset(void *s, int c, size_t n)
+{
+	unsigned char	*a;
+
+	a = s;
+	while (n > 0)
+	{
+		*a++ = (unsigned char)c;
+		n--;
+	}
+	return (s);
+}
diff --git a/ft_putchar.c b/ft_putchar.c
new file mode 100644
index 0000000..a4a871f
--- /dev/null
+++ b/ft_putchar.c
@@ -0,0 +1,23 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+void	ft_putchar(char c)
+{
+	write(1, &c, 1);
+}
diff --git a/ft_putchar_fd.c b/ft_putchar_fd.c
new file mode 100644
index 0000000..eb71264
--- /dev/null
+++ b/ft_putchar_fd.c
@@ -0,0 +1,45 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+void	ft_putchar_fd(char c, int fd)
+{
+	write(fd, &c, 1);
+}
+/*
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+int	main(void)
+{
+	int	fd;
+
+	if ((fd = open("test.txt", O_RDWR)) == -1)
+	{
+	printf("File Open Failed\n");
+	exit(0);
+	}
+	else
+	{
+	printf("File Opened Successfully\n");
+	printf("File Descriptor: %d\n", fd);
+	}
+	ft_putchar_fd('a', fd);
+}
+*/
diff --git a/ft_putendl_fd.c b/ft_putendl_fd.c
new file mode 100644
index 0000000..ab92f63
--- /dev/null
+++ b/ft_putendl_fd.c
@@ -0,0 +1,47 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+void	ft_putendl_fd(char *s, int fd)
+{
+	ft_putstr_fd(s, fd);
+	ft_putstr_fd("\n", fd);
+}
+/*
+#include <fcntl.h>
+#include <stdio.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+int	main(void)
+{
+	int	fd;
+
+	if ((fd = open("write.txt", O_RDWR)) == -1)
+	{
+	printf("File Open Failed\n");
+	exit(0);
+	}
+	else
+	{
+	printf("File Opened Successfully\n");
+	printf("File Descriptor: %d\n", fd);
+	}
+	ft_putendl_fd("abc", fd);
+}
+*/
diff --git a/ft_putnbr.c b/ft_putnbr.c
new file mode 100644
index 0000000..304be0a
--- /dev/null
+++ b/ft_putnbr.c
@@ -0,0 +1,39 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+void	ft_putnbr(int n)
+{
+	if (n == -2147483648)
+		ft_putstr("-2147483648");
+	else if (n < 0)
+	{
+		ft_putchar('-');
+		n = -n;
+		ft_putnbr(n);
+	}
+	else if (n == 0)
+		ft_putchar('0');
+	else if (n > 9)
+	{
+		ft_putnbr(n / 10);
+		ft_putchar((n % 10) + 48);
+	}
+	else
+		ft_putchar(n + 48);
+}
diff --git a/ft_putnbr_fd.c b/ft_putnbr_fd.c
new file mode 100644
index 0000000..db5ef2f
--- /dev/null
+++ b/ft_putnbr_fd.c
@@ -0,0 +1,98 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+void	ft_putnbr_fd(int n, int fd)
+{
+	if (n == -2147483648)
+		ft_putstr_fd("-2147483648", fd);
+	else if (n < 0)
+	{
+		ft_putchar_fd('-', fd);
+		n = -n;
+		ft_putnbr_fd(n, fd);
+	}
+	else if (n == 0)
+		ft_putchar_fd('0', fd);
+	else if (n > 9)
+	{
+		ft_putnbr_fd(n / 10, fd);
+		ft_putchar_fd((n % 10) + 48, fd);
+	}
+	else
+		ft_putchar_fd(n + 48, fd);
+}
+/*
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+int	main(void)
+{
+	int	fd;
+
+	if ((fd = open("write.txt", O_RDWR)) == -1)
+	{
+		printf("File Open Failed\n");
+		exit(0);
+	}
+	else
+	{
+		printf("File Opened Successfully\n");
+		printf("File Descriptor: %d\n", fd);
+	}
+// ft_putnbr_fd(0, fd);
+// ft_putnbr_fd(5, fd);
+//		ft_putnbr_fd(442, fd);
+//		ft_putnbr_fd(-5, fd);
+//		ft_putnbr_fd(-57, fd);
+//		ft_putnbr_fd(164189, fd);
+//		ft_putnbr_fd(-987441, fd);
+//		ft_putnbr_fd(2147483647, fd);
+	ft_putnbr_fd(-2147483648LL, fd);
+}
+*/
+
+/*
+void	ft_putnbr_helper(long nl, int fd)
+{
+	if (nl < 0)
+	{
+		ft_putchar_fd('-', fd);
+		nl = -nl;
+		ft_putnbr_helper(nl, fd);
+	}
+	else if (nl == 0)
+		ft_putchar_fd('0', fd);
+	else if (nl > 9)
+	{
+		ft_putnbr_helper(nl / 10, fd);
+		ft_putchar_fd((nl % 10) + '0', fd);
+	}
+	else
+		ft_putchar_fd((nl + '0'), fd);
+}
+
+void	ft_putnbr_fd(int n, int fd)
+{
+	long	nl;
+
+	nl = n;
+	ft_putnbr_helper(nl, fd);
+}
+*/
diff --git a/ft_putstr.c b/ft_putstr.c
new file mode 100644
index 0000000..2329e32
--- /dev/null
+++ b/ft_putstr.c
@@ -0,0 +1,24 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+void	ft_putstr(char *s)
+{
+	write(1, s, ft_strlen(s));
+}
+
diff --git a/ft_putstr_fd.c b/ft_putstr_fd.c
new file mode 100644
index 0000000..a25e75d
--- /dev/null
+++ b/ft_putstr_fd.c
@@ -0,0 +1,46 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+void	ft_putstr_fd(char *s, int fd)
+{
+	write(fd, s, ft_strlen(s));
+}
+
+/*
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+int	main(void)
+{
+	int	fd;
+
+	if ((fd = open("test.txt", O_RDWR)) == -1)
+	{
+	printf("File Open Failed\n");
+	exit(0);
+	}
+	else
+	{
+	printf("File Opened Successfully\n");
+	printf("File Descriptor: %d\n", fd);
+	}
+	ft_putstr_fd("abc", fd);
+}
+*/
diff --git a/ft_split.c b/ft_split.c
new file mode 100644
index 0000000..b5d8a8b
--- /dev/null
+++ b/ft_split.c
@@ -0,0 +1,105 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+static int	ft_countword(char const *s, char c)
+{
+	int	i;
+	int	wordcounter;
+
+	i = 0;
+	wordcounter = 0;
+	while (s[i])
+	{
+		if (s[i] == c)
+			i++;
+		else
+		{
+			wordcounter++;
+			while (s[i] != c && s[i])
+				i++;
+		}
+	}
+	return (wordcounter);
+}
+
+static char	**ft_addwords(char **a, char const *s, char c, int wordcounter)
+{
+	int	i;
+	int	start;
+	int	word;
+
+	i = 0;
+	word = 0;
+	while (wordcounter--)
+	{
+		while (s[i] == c)
+			i++;
+		start = i;
+		while (s[i] != c && s[i] != 0)
+			i++;
+		a[word] = ft_substr(s, start, i - start);
+		if (!a[word])
+		{
+			while (word-- >= 0)
+				free(a[word]);
+			return (free(a), NULL);
+		}
+		word++;
+		i++;
+	}
+	return (a[word] = 0, a);
+}
+
+char	**ft_split(char const *s, char c)
+{
+	char	**a;
+	int		wordcounter;
+
+	wordcounter = ft_countword(s, c);
+	a = malloc(sizeof(a) * (wordcounter + 1));
+	if (!a)
+		return (NULL);
+	a = ft_addwords(a, s, c, wordcounter);
+	return (a);
+}
+
+/*
+#include <stdio.h>
+
+int	main(void)
+{
+	char	**b;
+	int		i;
+	char	*s2;
+
+	// char	*s= "xxxhelloxxallxxofxyoux";
+	s2 = "  code  42  ";
+	// char	**a;
+	// a = ft_split(s, 'x');
+	b = ft_split(s2, ' ');
+	i = 0;
+	while (b[i])
+	{
+		printf("b[%i]: %s\n", i, b[i]);
+		free(b[i]);
+		i++;
+	}
+	free(b);
+}
+*/
diff --git a/ft_strchr.c b/ft_strchr.c
new file mode 100644
index 0000000..b7d10a6
--- /dev/null
+++ b/ft_strchr.c
@@ -0,0 +1,64 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+char	*ft_strchr(const char *s, int c)
+{
+	size_t	i;
+	size_t	size;
+
+	size = ft_strlen(s);
+	i = 0;
+	while (i <= size)
+	{
+		if (s[i] == (char)c)
+			return ((char *)&s[i]);
+		i++;
+	}
+	return (NULL);
+}
+/*
+
+#include <string.h>
+
+int	main(void)
+{
+	const char	s[6] = "Hello0";
+	int			c;
+	int			d;
+	int			e;
+	int			f;
+	int			g;
+
+	c = (int) 'e';
+	d = (int) 'm';
+	e = (int) '8';
+	f = (int) '0';
+	g = (int) '$';
+	printf("%s\n", ft_strchr(s, c));
+	printf("%s\n", strchr(s, c));
+	printf("%s\n", ft_strchr(s, d));
+	printf("%s\n", strchr(s, d));
+	printf("%s\n", ft_strchr(s, e));
+	printf("%s\n", strchr(s, e));
+	printf("%s\n", ft_strchr(s, f));
+	printf("%s\n", strchr(s, f));
+	printf("%s\n", ft_strchr(s, g));
+	printf("%s\n", strchr(s, g));
+}
+*/
diff --git a/ft_strdup.c b/ft_strdup.c
new file mode 100644
index 0000000..dbad4af
--- /dev/null
+++ b/ft_strdup.c
@@ -0,0 +1,58 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+char	*ft_strdup(const char *s)
+{
+	char	*ptr;
+
+	ptr = (char *)malloc(ft_strlen(s) + 1);
+	if (!ptr)
+		return (NULL);
+	ft_strlcpy(ptr, s, ft_strlen(s) + 1);
+	return (ptr);
+}
+/*
+#include <stdio.h>
+#include <string.h>
+
+int	main(void)
+{
+	char	s27[] = "Hello";
+	char	s28[] = "Hello";
+	char	*result1;
+	char	*result1b;
+	char	emptystring[] = "";
+	char	*result2;
+	char	*result2b;
+
+	printf("################ strdup ##############\n");
+	result1 = ft_strdup(s27);
+	printf("ft_strdup: %s\n", result1);
+	free(result1);
+	result1b = strdup(s28);
+	printf("strdup: %s\n", result1b);
+	free(result1b);
+	result2 = ft_strdup(emptystring);
+	printf("ft_strdup: %s\n", result2);
+	free(result2);
+	result2b = strdup(emptystring);
+	printf("strdup: %s\n", result2b);
+	free(result2b);
+}
+*/
diff --git a/ft_striteri.c b/ft_striteri.c
new file mode 100644
index 0000000..61a02d0
--- /dev/null
+++ b/ft_striteri.c
@@ -0,0 +1,45 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+void	ft_striteri(char *s, void (*f)(unsigned int, char *))
+{
+	int	i;
+
+	i = 0;
+	while (s[i])
+	{
+		f(i, &s[i]);
+		i++;
+	}
+}
+/*
+void	tmp(unsigned int i, char* s)
+{
+	i = 0;
+	*s = ft_toupper(*s);
+}
+
+int	main(void)
+{
+	char	s[] = " abcd";
+
+	ft_striteri(s, tmp);
+	printf("%s\n", s);
+}
+*/
diff --git a/ft_strjoin.c b/ft_strjoin.c
new file mode 100644
index 0000000..ecc7f9a
--- /dev/null
+++ b/ft_strjoin.c
@@ -0,0 +1,40 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+char	*ft_strjoin(char const *s1, char const *s2)
+{
+	char	*ptr;
+
+	ptr = malloc(ft_strlen(s1) + ft_strlen(s2) + 1);
+	if (!ptr)
+		return (NULL);
+	ft_strlcpy(ptr, s1, (ft_strlen(s1) + 1));
+	ft_strlcat(ptr, s2, (ft_strlen(s1) + ft_strlen(s2) + 1));
+	return (ptr);
+}
+/*
+#include <stdio.h>
+
+int	main(void)
+{
+	char const	s1[]= "Hello, ";
+	char const	s2[]= "World";
+	printf("after: %s\n", ft_strjoin(s1, s2));
+}
+*/
diff --git a/ft_strlcat.c b/ft_strlcat.c
new file mode 100644
index 0000000..ba2434d
--- /dev/null
+++ b/ft_strlcat.c
@@ -0,0 +1,53 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+size_t	ft_strlcat(char *dest, const char *src, size_t size)
+{
+	const size_t	dlen = ft_strlen(dest);
+	const size_t	slen = ft_strlen(src);
+
+	if (dlen >= size)
+		return (size + slen);
+	if (slen < size - dlen)
+		ft_memcpy(dest + dlen, src, slen + 1);
+	else
+	{
+		ft_memcpy(dest + dlen, src, size - dlen - 1);
+		dest[size - 1] = '\0';
+	}
+	return (dlen + slen);
+}
+/*
+size_t	ft_strlcat(char *dest, const char *src, size_t size)
+{
+	const size_t	dlen = ft_strlen(dest);
+	const size_t	slen = ft_strlen(src);
+	size_t			i;
+
+	if (dlen >= size)
+		return (size + slen);
+	dest += dlen;
+	i = slen;
+	size -= dlen;
+	while (--size && i--)
+		*dest++ = *src++;
+	*dest = 0;
+	return (dlen + slen);
+}
+*/
diff --git a/ft_strlcpy.c b/ft_strlcpy.c
new file mode 100644
index 0000000..489cc18
--- /dev/null
+++ b/ft_strlcpy.c
@@ -0,0 +1,51 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+size_t	ft_strlcpy(char *dest, const char *src, size_t size)
+{
+	unsigned int	i;
+
+	i = 0;
+	if (size > 0)
+	{
+		while (src[i] && i < (size - 1))
+		{
+			dest[i] = src[i];
+			i++;
+		}
+		dest[i] = '\0';
+	}
+	return (ft_strlen(src));
+}
+/*
+#include <stdio.h>
+
+int	main(void)
+{
+	char			dest[6];
+	unsigned int	size;
+
+	char	src[]="Hello";
+	int	return_value ;
+	size = 3;
+	return_value = ft_strlcpy(dest, src, size);
+	printf("%d\n", return_value);
+	printf("%s, %s\n", dest, src);
+}
+*/
diff --git a/ft_strlen.c b/ft_strlen.c
new file mode 100644
index 0000000..8483574
--- /dev/null
+++ b/ft_strlen.c
@@ -0,0 +1,39 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+size_t	ft_strlen(const char *s)
+{
+	int	i;
+
+	i = 0;
+	while (s[i])
+		i++;
+	return (i);
+}
+/*
+#include <stdio.h>
+#include <string.h>
+
+int	main(void)
+{
+	const char	s[]= "Hello";
+	printf("%zu\n", ft_strlen(s));
+	printf("%zu\n", strlen(s));
+}
+*/
diff --git a/ft_strmapi.c b/ft_strmapi.c
new file mode 100644
index 0000000..a7d5c54
--- /dev/null
+++ b/ft_strmapi.c
@@ -0,0 +1,68 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+char	*ft_strmapi(char const *s, char (*f)(unsigned int, char))
+{
+	int		i;
+	char	*newstring;
+
+	newstring = malloc(sizeof(char) * (ft_strlen(s) + 1));
+	if (!newstring)
+		return (NULL);
+	i = 0;
+	while (s[i])
+	{
+		newstring[i] = f(i, s[i]);
+		i++;
+	}
+	newstring[i] = '\0';
+	return (newstring);
+}
+
+/*
+
+#include <stdio.h>
+
+char	addOne(unsigned int i, char c)
+{
+	return (i + c);
+}
+
+int	main(void)
+{
+		char * s = ft_strmapi("1234", addOne);
+	printf("%s\n", s);
+	free(s);
+		s = ft_strmapi("", addOne);
+	printf("%s\n", s);
+	free(s);
+		return (0);
+}
+char	tmp(unsigned int i, char c)
+{
+	i = 0;
+	return(ft_toupper(c));
+}
+int	main(void)
+{
+	char	s[] = "abc";
+
+	printf("%s\n", ft_strmapi(s, tmp));
+}
+*/
diff --git a/ft_strncmp.c b/ft_strncmp.c
new file mode 100644
index 0000000..d4858dc
--- /dev/null
+++ b/ft_strncmp.c
@@ -0,0 +1,73 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+int	ft_strncmp(const char *s1, const char *s2, size_t n)
+{
+	size_t	i;
+
+	i = 0;
+	while (i < n)
+	{
+		if ((s1[i] != s2[i]) || s1[i] == '\0')
+			return ((unsigned char)s1[i] - (unsigned char)s2[i]);
+		i++;
+	}
+	return (0);
+}
+/*
+#include <stdio.h>
+#include <string.h>
+
+int	main(void)
+{
+	char	str1[] = "ABC";
+	char	str2[] = "ABC";
+	char	str3[] = "AB";
+	char	str4[] = "ABA";
+	char	str5[] = "ABZ";
+	char	str6[] = "ABJ";
+	int		size;
+
+	printf("############ strncmp ############\n");
+	size = 3;
+	printf("%d\n", ft_strncmp(str1, str2, size));
+	printf("%d\n", strncmp(str1, str2, size));
+	size = 0;
+	printf("%d\n", ft_strncmp(str1, str1, size));
+	printf("%d\n", strncmp(str1, str1, size));
+	size = -1;
+	printf("%d\n", ft_strncmp(str1, str1, size));
+	printf("%d\n", strncmp(str1, str1, size));
+	size = 3;
+	printf("%d\n", ft_strncmp(str1, str3, size));
+	printf("%d\n", strncmp(str1, str3, size));
+	size = 3;
+	printf("%d\n", ft_strncmp(str4, str5, size));
+	printf("%d\n", strncmp(str4, str5, size));
+	size = 3;
+	printf("%d\n", ft_strncmp(str6, str1, size));
+	printf("%d\n", strncmp(str6, str1, size));
+	size = 6;
+	printf("%d\n", ft_strncmp("test\200", "test\0", size));
+	printf("%d\n", strncmp("test\200", "test\0", size));
+	size = 4;
+	printf("%d\n", ft_strncmp("\201", "A", size));
+	printf("%d\n", strncmp("\201", "A", size));
+}
+*/
diff --git a/ft_strnstr.c b/ft_strnstr.c
new file mode 100644
index 0000000..f7042d6
--- /dev/null
+++ b/ft_strnstr.c
@@ -0,0 +1,113 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+char	*ft_strnstr(const char *big, const char *little, size_t len)
+{
+	unsigned long	i;
+	int				j;
+
+	if (ft_strlen(little) <= 0)
+		return ((char *)(big));
+	i = 0;
+	while (big[i] != '\0' && i < len)
+	{
+		if (big[i] == little[0])
+		{
+			j = 0;
+			while (big[i + j] == little[j] && little[j] && (i + j) < len)
+				j++;
+			if (little[j] == '\0')
+				return ((char *)(&big[i]));
+		}
+		i++;
+	}
+	return (NULL);
+}
+/*
+#include <bsd/string.h>
+#include <stdio.h>
+#include <string.h>
+
+int	main(void)
+{
+		const char *largestring = "Foo Bar Caz";
+		const char *smallstring = "Bar";
+		const char *empty_smallstring = "";
+		const char *largestring2 = "Foo Baz Caz";
+		const char *smallstring2 = "Bar";
+		const char *largestring3 = "Foo Bar Baz";
+		const char *smallstring3 = "Baz";
+
+	printf("  the big string is: %s\n", largestring);
+	printf("the small string is: %s\n", smallstring);
+		printf("            strnstr: %s\n",
+strnstr(largestring, smallstring, 7));
+		printf("         ft_strnstr: %s\n",
+ft_strnstr(largestring, smallstring, 7));
+	printf("----------------------------------
+---------------------------------\n");
+	printf("When the small string is empty,
+ the function returns the big string\n");
+	printf("  the big string is: %s\n", largestring);
+	printf("the small string is: %s\n", empty_smallstring);
+		printf("            strnstr: %s\n",
+strnstr(largestring, empty_smallstring, 7));
+		printf("         ft_strnstr: %s\n",
+ft_strnstr(largestring, empty_smallstring, 7));
+	printf("------------------------------
+-------------------------------------\n");
+	printf("When the little string occurs
+nowhere in big, NULL is returned\n");
+	printf("  the big string is: %s\n", largestring2);
+	printf("the small string is: %s\n", smallstring2);
+		printf("            strnstr: %s\n",
+strnstr(largestring2, smallstring2, 7));
+		printf("         ft_strnstr: %s\n",
+ft_strnstr(largestring2, smallstring2, 7));
+	printf("-------------------------------
+------------------------------------\n");
+	printf("When the little string occurs
+at the end of big\n");
+	printf("  the big string is: %s\n", largestring3);
+	printf("the small string is: %s\n", smallstring3);
+		printf("            strnstr: %s\n",
+strnstr(largestring3, smallstring3, 11));
+		printf("         ft_strnstr: %s\n",
+ft_strnstr(largestring3, smallstring3, 11));
+	printf("-----------------------------------
+--------------------------------\n");
+	printf("When length is smaller than
+necessary to print little\n");
+	printf("  the big string is: %s\n", largestring3);
+	printf("the small string is: %s\n", smallstring3);
+		printf("            strnstr: %s\n",
+strnstr(largestring3, smallstring3, 10));
+		printf("         ft_strnstr: %s\n",
+ft_strnstr(largestring3, smallstring3, 10));
+	printf("----------------------------
+---------------------------------------\n");
+	printf("When length is zero\n");
+	printf("  the big string is: %s\n", largestring3);
+	printf("the small string is: %s\n", smallstring3);
+		printf("            strnstr: %s\n",
+strnstr(largestring3, smallstring3, 0));
+		printf("         ft_strnstr: %s\n",
+ft_strnstr(largestring3, smallstring3, 0));
+}
+*/
diff --git a/ft_strrchr.c b/ft_strrchr.c
new file mode 100644
index 0000000..17dfcb5
--- /dev/null
+++ b/ft_strrchr.c
@@ -0,0 +1,86 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+char	*ft_strrchr(const char *s, int c)
+{
+	int	slen;
+
+	slen = ft_strlen(s);
+	while (slen >= 0)
+	{
+		if (s[slen] == (char)c)
+			return ((char *)&s[slen]);
+		slen--;
+	}
+	return (0);
+}
+
+/*
+char	*ft_strrchr(const char *p, int ch)
+{
+	int	i;
+
+	i = 0;
+	while (s[i])
+		i++;
+	while (s[i] != (char)c)
+		if (i-- == 0)
+			return (NULL);
+	return ((char *)&s[i]);
+}
+
+char	*ft_strrchr(const char *p, int ch)
+{
+	char	*save;
+
+	save = NULL;
+	while (1)
+	{
+		if (*p == (char)ch)
+			save = (char *)p;
+		if (!*p++)
+			return (save);
+	}
+}
+
+#include <string.h>
+
+int	main(void)
+{
+	const char	s[] = "Helleo";
+	int			i;
+	int			j;
+	int			k;
+
+	i = (int) 'i';
+	j = (int) 'e';
+	k = '\0';
+	printf("Expected return: NULL\n");
+	printf("ft_strrchr: %s\n", ft_strrchr(s, i));
+	printf("   strrchr: %s\n", strrchr(s, i));
+	printf("------------------------\n");
+	printf("Expected return: 'eo'\n");
+	printf("ft_strrchr: %s\n", ft_strrchr(s, j));
+	printf("   strrchr: %s\n", strrchr(s, j));
+	printf("------------------------\n");
+	printf("Expected return: 'null byte'\n");
+	printf("ft_strrchr: %s\n", ft_strrchr(s, k));
+	printf("   strrchr: %s\n", strrchr(s, k));
+}
+*/
diff --git a/ft_strtrim.c b/ft_strtrim.c
new file mode 100644
index 0000000..fe217f6
--- /dev/null
+++ b/ft_strtrim.c
@@ -0,0 +1,92 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+char	*ft_strtrim(char const *s1, char const *set)
+{
+	int		i;
+	char	*ptr;
+	int		start;
+	int		end;
+	int		slen;
+
+	i = 0;
+	while (s1[i] && ft_strchr(set, s1[i]))
+		i++;
+	start = i;
+	slen = ft_strlen(s1);
+	i = 0;
+	while (s1[slen - i - 1] && ft_strchr(set, s1[slen - i - 1]))
+		i++;
+	end = i;
+	ptr = ft_substr(s1, start, (slen - start - end));
+	return (ptr);
+}
+/*
+#include <stdio.h>
+
+int	main(void)
+{
+		printf("%s\n", ft_strtrim("   xxxtripouille", " x"));
+		printf("%s\n", ft_strtrim("tripouille   xxx", " x"));
+		printf("%s\n", ft_strtrim("   xxxtripouille   xxx", " x"));
+		printf("%s\n", ft_strtrim("   xxx   xxx", " x"));
+		printf("%s\n", ft_strtrim("", "123"));
+		printf("%s\n", ft_strtrim("123", ""));
+		printf("%s\n", ft_strtrim("", ""));
+		printf("%s\n", ft_strtrim("abcdba", "acb"));
+		return (0);
+}
+
+#include <stdio.h>
+
+int	main(void)
+{
+	char	s1[] = "lorem \n ipsum \t dolor \n sit \t amet";
+	char	s2[] = "lorem ipsum dolor sit amet \n \t ";
+	char	s3[] = " \n \t lorem ipsum dolor sit amet";
+	char	s4[] = "  \n  \t  lorem \n ipsum \t dolor \n sit \t amet  \t \n ";
+	char	s5[] = "          ";
+
+		char    set [] = "\t \n";
+	printf("%s\n", ft_strtrim(s1, set));
+	printf("\n");
+	printf("%s\n", ft_strtrim(s2, set));
+	printf("\n");
+	printf("%s\n", ft_strtrim(s3, set));
+	printf("\n");
+	printf("%s\n", ft_strtrim(s4, set));
+	printf("\n");
+	printf("%s\n", ft_strtrim(s5, set));
+	printf("\n");
+		return (0);
+}
+
+int	main(void)
+{
+	char const	s1[]= "asasHello, World.asas";
+	char const	s2[]= "asasasHello, World.asasasasas";
+	char const	s3[]= "abcabcabcabcHelloabc, World.abcabcabc";
+	char const	set1[]= "as";
+	char const	set1bis[]= "as";
+	char const	set3[]= "abc";
+	printf("%s\n", ft_strtrim(s1, set1));
+	printf("%s\n", ft_strtrim(s2, set1bis));
+	printf("%s\n", ft_strtrim(s3, set3));
+}
+*/
diff --git a/ft_substr.c b/ft_substr.c
new file mode 100644
index 0000000..b1431c8
--- /dev/null
+++ b/ft_substr.c
@@ -0,0 +1,59 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+char	*ft_substr(char const *s, unsigned int start, size_t len)
+{
+	char	*ptr;
+	size_t	s_len;
+	size_t	ptr_len;
+
+	if (!s)
+		return (NULL);
+	s_len = ft_strlen(s);
+	if (s_len <= start)
+		return (ft_strdup(""));
+	else if (s_len > start + len)
+		ptr_len = len;
+	else
+		ptr_len = s_len - start;
+	ptr = malloc(ptr_len + 1);
+	ft_strlcpy(ptr, &s[start], ptr_len + 1);
+	return (ptr);
+}
+
+/*
+#include <stdio.h>
+
+int	main(void)
+{
+	char	s[] = "lorem ipsum dolor sit amet";
+	char	*ptr;
+
+	ptr = ft_substr(s, 6, 6);
+	printf("%s\n", ptr);
+	free(ptr);
+	printf("%s\n", ft_substr("", 0, 1));
+	printf("%s\n", ft_substr(s, 15, 1));
+	printf("%s\n", ft_substr(s, 0, 10));
+	printf("%s\n", ft_substr(s, 7, 10));
+	printf("%s\n", ft_substr(s, 7, 0));
+	printf("%s\n", ft_substr(s, 0, 0));
+	printf("%s\n", ft_substr(s, 400, 20));
+}
+*/
diff --git a/ft_tolower.c b/ft_tolower.c
new file mode 100644
index 0000000..070740b
--- /dev/null
+++ b/ft_tolower.c
@@ -0,0 +1,55 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+char	ft_tolower(int c)
+{
+	if ((c >= 65) && (c <= 90))
+	{
+		c += 32;
+		return (c);
+	}
+	else
+		return (c);
+}
+/*
+int	main(void)
+{
+	int	l;
+	int	m;
+	int	n;
+	int	o;
+
+	l = 64;
+	m = 65;
+	n = 90;
+	o = 91;
+	printf("-----------------\n");
+	printf("%i\n", ft_tolower(l));
+	printf("%i\n", tolower(l));
+	printf("-----------------\n");
+	printf("%i\n", ft_tolower(m));
+	printf("%i\n", tolower(m));
+	printf("-----------------\n");
+	printf("%i\n", ft_tolower(n));
+	printf("%i\n", tolower(n));
+	printf("-----------------\n");
+	printf("%i\n", ft_tolower(o));
+	printf("%i\n", tolower(o));
+}
+*/
diff --git a/ft_toupper.c b/ft_toupper.c
new file mode 100644
index 0000000..5ed5854
--- /dev/null
+++ b/ft_toupper.c
@@ -0,0 +1,55 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "libft.h"
+
+char	ft_toupper(int c)
+{
+	if ((c >= 97) && (c <= 122))
+		c -= 32;
+	return (c);
+}
+/*
+int	main(void)
+{
+	int	i;
+	int	j;
+	int	k;
+	int	l;
+
+	i = 96;
+	j = 97;
+	k = 122;
+	l = 123;
+	printf("-----------------\n");
+	printf("for 96 ascii i.e. backtick\n");
+	printf("%i\n", ft_toupper(i));
+	printf("%i\n", toupper(i));
+	printf("-----------------\n");
+	printf("for 97 ascii i.e. 'a'\n");
+	printf("%i\n", ft_toupper(j));
+	printf("%i\n", toupper(j));
+	printf("-----------------\n");
+	printf("for 122 ascii i.e. 'z'\n");
+	printf("%i\n", ft_toupper(k));
+	printf("%i\n", toupper(k));
+	printf("-----------------\n");
+	printf("for 123 ascii i.e. '{'\n");
+	printf("%i\n", ft_toupper(l));
+	printf("%i\n", toupper(l));
+}
+*/
diff --git a/libft.h b/libft.h
new file mode 100644
index 0000000..f649d10
--- /dev/null
+++ b/libft.h
@@ -0,0 +1,92 @@
+/*
+Libft Copyright (C) 2026 yctct
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#ifndef LIBFT_H
+
+# define LIBFT_H
+
+# include <stddef.h> // for size_t
+# include <stdlib.h> // for free
+# include <unistd.h> // for write in ft_putnbr_fd.c
+
+typedef struct s_list
+{
+	void			*content;
+	struct s_list	*next;
+}					t_list;
+
+int					ft_atoi(const char *nptr);
+void				ft_bzero(void *s, size_t n);
+int					ft_isalpha(int c);
+int					ft_isdigit(int c);
+int					ft_isalnum(int c);
+int					ft_isalpha(int c);
+int					ft_isascii(int c);
+int					ft_isdigit(int c);
+int					ft_isprint(int c);
+void				*ft_memchr(const void *s, int c, size_t n);
+void				*ft_memcpy(void *dest, const void *src, size_t n);
+void				*ft_memmove(void *dest, const void *src, size_t n);
+void				*ft_memset(void *s, int c, size_t n);
+int					ft_memcmp(const void *s1, const void *s2, size_t n);
+char				*ft_strchr(const char *s, int c);
+size_t				ft_strlen(const char *s);
+int					ft_strclen(const char *str);
+int					ft_strncmp(const char *s1, const char *s2, size_t n);
+char				*ft_strnstr(const char *big, const char *little,
+						size_t len);
+char				*ft_strrchr(const char *s, int c);
+char				ft_tolower(int c);
+char				ft_toupper(int c);
+void				*malloc(size_t size);
+void				*ft_calloc(size_t nmemb, size_t size);
+char				*ft_strdup(const char *s);
+char				*ft_substr(char const *s, unsigned int start, size_t len);
+char				*ft_strjoin(char const *s1, char const *s2);
+char				*ft_strtrim(char const *s1, char const *set);
+char				*ft_itoa(int n);
+char				*ft_strmapi(char const *s, char (*f)(unsigned int, char));
+void				ft_striteri(char *s, void (*f)(unsigned int, char *));
+void				ft_putchar_fd(char c, int fd);
+void				ft_putchar(char c);
+ssize_t				write(int fd, const void *buf, size_t count);
+void				ft_putstr_fd(char *s, int fd);
+void				ft_putstr(char *s);
+void				ft_putendl_fd(char *s, int fd);
+void				ft_putnbr_fd(int n, int fd);
+void				ft_putnbr(int n);
+size_t				ft_strlcat(char *dest, const char *src, size_t size);
+size_t				ft_strlen(const char *str);
+size_t				ft_strlcpy(char *dest, const char *src, size_t size);
+void				ft_striteri(char *s, void (*f)(unsigned int, char *));
+char				*ft_strmapi(char const *s, char (*f)(unsigned int, char));
+char				**ft_split(char const *s, char c);
+t_list				*ft_lstnew(void *content);
+void				ft_lstadd_front(t_list **lst, t_list *new);
+int					ft_lstsize(t_list *lst);
+t_list				*ft_lstlast(t_list *lst);
+void				ft_lstadd_back(t_list **lst, t_list *new);
+void				ft_lstdelone(t_list *lst, void (*del)(void *));
+void				ft_lstclear(t_list **lst, void (*del)(void *));
+void				ft_lstiter(t_list *lst, void (*f)(void *));
+t_list				*ft_lstmap(t_list *lst, void *(*f)(void *),
+						void (*del)(void *));
+void				ft_lstiter(t_list *lst, void (*f)(void *));
+t_list				*ft_lstmap(t_list *lst, void *(*f)(void *),
+						void (*del)(void *));
+
+#endif