官方解答：
Functions
Copying:
memcpy
Copy block of memory (function)
memmove
Move block of memory (function )
strcpy
Copy string (function)
strncpy
Copy characters from string (function)

Concatenation:
strcat
Concatenate strings (function)
strncat
Append characters from string (function)

Comparison:
memcmp
Compare two blocks of memory (function)
strcmp
Compare two strings (function )
strcoll
Compare two strings using locale (function)
strncmp
Compare characters of two strings (function)
strxfrm
Transform string using locale (function)

Searching:
memchr
Locate character in block of memory (function)
strchr
Locate first occurrence of character in string (function)
strcspn
Get span until character in string (function)
strpbrk
Locate character in string (function)
strrchr
Locate last occurrence of character in string (function)
strspn
Get span of character set in string (function)
strstr
Locate substring (function)
strtok
Split string into tokens (function)

Other:
memset
Fill block of memory (function)
strerror
Get pointer to error message string (function)
strlen
Get string length (function )

Macros
NULL
Null pointer (macro)

Types
size_t
Unsigned integral type (type)