README.md

0x05. C - Pointers, arrays and strings.

Resources

• Pointers, arrays and Data Structures
• C - Pointer to Pointer
• C - Pointer to Pointer with Example
• C - Multidimensional Arrays in C
• Two dimensional (2D) arrays in C programming with example
• C Books and PDF's to check out and use as reference.

Tasks

0. memset : A function that fills memory with a constant byte.
   • Prototype: char *_memset(char *s, char b, unsigned int n);
   • The _memset() function fills the first n bytes of the memory area pointed to by s with the constant byte b.
   • Returns a pointer to the memory area s.
   • Read more on memset here
   • FYI: The standard library provides a similar function: memset. Run man memset to learn more.
   • Compile the code this way: gcc -Wall -pedantic -Werror -Wextra -std=gnu89 0-main.c 0-memset.c -o 0-memset
1. memcpy : A function that copies the memory area.
   • Prototype: char *_memcpy(char *dest, char *src, unsigned int n);
   • The _memcpy() function copies n bytes from the memory area src to the memory area dest.
   • Returns a pointer to dest
   • FYI: The standard library provides a similar function: memcpy. Run man memcpy to learn more.
   • Compile the code this way: gcc -Wall -pedantic -Werror -Wextra -std=gnu89 1-main.c 1-memcpy.c -o 1-memcpy
2. strchr : A function that locates a character in a string.
   • Prototype: char *_strchr(char *s, char c);
   • Returns a pointer to the first occurrence of the character c in the string s, or NULL if the character is not found.
   • FYI: The standard library provides a similar function: strchr. Run man strchr to learn more.
   • Read more here on strchr.
   • Compile the code this way: gcc -Wall -pedantic -Werror -Wextra -std=gnu89 2-main.c 2-strchr.c -o 2-strchr
3. strspn : A function that gets the length of a prefix substring.
   • Prototype: unsigned int _strspn(char *s, char *accept);
   • Returns the number of bytes in the initial segment of s which consist only of bytes from accept.
   • FYI: The standard library provides a similar function: strspn. Run man strspn to learn more.
   • Compile the code this way: gcc -Wall -pedantic -Werror -Wextra -std=gnu89 3-main.c 3-strspn.c -o 3-strspn
4. strpbrk : A function that searches a string for any of a set of bytes.
   • Prototype: char *_strpbrk(char *s, char *accept);
   • The _strpbrk() function locates the first occurrence in the string s of any of the bytes in the string accept.
   • Returns a pointer to the byte in s that matches one of the bytes in accept, or NULL if no such byte is found.
   • FYI: The standard library provides a similar function: strpbrk. Run man strpbrk to learn more.
   • Compile the code this way: gcc -Wall -pedantic -Werror -Wextra -std=gnu89 4-main.c 4-strpbrk.c -o 4-strpbrk
5. strstr : A function that locates a substring.
   • Prototype: char *_strstr(char *haystack, char *needle);
   • The _strstr() function finds the first occurrence of the substring needle in the string haystack.
   • The terminating null bytes ('\0') are not compared.
   • Returns a pointer to the beginning of the located substring, or NULL if the substring is not found.
   • FYI: The standard library provides a similar function: strstr. Run man strstr to learn more.
   • Compile the code this way: gcc -Wall -pedantic -Werror -Wextra -std=gnu89 5-main.c 5-strstr.c -o 5-strstr
6. Chess is mental torture : A function that prints the chessboard.
   • Prototype: void print_chessboard(char (*a)[8]);
   • Compile the code this way: gcc -Wall -pedantic -Werror -Wextra -std=gnu89 _putchar.c 7-main.c 7-print_chessboard.c -o 7-print_chessboard
7. The line of life is a ragged diagonal between duty and desire : A function that prints the sum of the two diagonals of a square matrix of integers.
   • Prototype: void print_diagsums(int *a, int size);
   • Format: see main code.
   • You are allowed to use the standard library.
   • Note: that in the following example we are casting an int[][] into an int*.
     • This is not something you should do. The goal here is to make sure you understand how an array of array is stored in memory.
   • Compile the code this way: gcc -Wall -pedantic -Werror -Wextra -std=gnu89 8-main.c 8-print_diagsums.c -o 8-print_diagsums