Available in the string.h header file are the following routines
strcat(string1,string2);
This joins string2 to string1; care must be taken to allocate enough space for the answer
strchr(string,character);
This locates the position of the first occurrence of the character within the string and returns the address of that character i.e. a Find
strcmp(string1,string2);
This compares string2 to string1, if no difference if found a NULL character is returned else the address of the first non matching character.
strcpy(string1,string2);
The copies the string2 into string1
strlen(string);
Returns the length of the string
isalpha(character);
Returns a non-zero number if the character is a letter, otherwise a zero is returned
isupper(character);
Returns a non-zero number if the character is uppercase, otherwise a zero is returned
islower(character);
Returns a non-zero number if the character is lower case, otherwise a zero is returned
isdigit(character);
Returns a non-zero number if the character is a digit i.e. 0-9, otherwise a zero is returned
toupper(character);
Returns the upper case version of the character
tolower (character);
Returns the lower case version of the character