String.h

Functions for length, copying, and concatenation.

Function	Description	Example
`size_t strlen(const char *str)`	Get the length of a string (excluding null terminator)	strlen("Code") //4
`char* strcpy(char dest, const char src)`	Copy one string to another	strcpy(buff, "Hi"); //buff becomes "Hi"
`char* strncpy(char dest, const char src, size_t n)`	Copy at most n characters	strncpy(buff, "Hello", 3); //buff becomes "Hel"
`char* strcat(char dest, const char src)`	Concatenate (append) source to destination	strcat(buff, " World");

Functions to compare two strings lexicographically.

Function	Description	Example
`int strcmp(const char s1, const char s2)`	Compare two strings	strcmp("A", "B") // -1 (Negative) strcmp("A", "A") // 0
`int strncmp(const char s1, const char s2, size_t n)`	Compare up to n characters	strncmp("apple", "apply", 4) // 0 (First 4 chars match)

Functions for finding characters or substrings.

Function	Description	Example
`char* strchr(const char *str, int c)`	Locate first occurrence of a character	strchr("hello", 'e')
`char* strstr(const char haystack, const char needle)`	Locate the first occurrence of a substring	strstr("banana", "nan")
`char* strtok(char str, const char delim)`	Split string into tokens	strtok(str, ",") Returns next token

Functions that operate on raw memory buffers (not just strings).

Function	Description	Example
`void* memset(void *str, int c, size_t n)`	Fill memory with a constant byte	memset(buff, 0, 10); (Zero out buffer)
`void* memcpy(void dest, const void src, size_t n)`	Copy memory block (regions must not overlap)	memcpy(d, s, sizeof(int)*5);
`void* memmove(void dest, const void src, size_t n)`	Copy memory block (handles overlapping regions safe)	memmove(&arr[1], &arr[0], n);