String functions are the key points of computer programming for library automation. In this paper the primary string functions, compute string length, extract some characters from a string, search specific characters in a string and concatenate two or more strings or characters are introduced in BASIC language first, then the application of these functions in KWIC, KWOC, OCLC's title search key and MARC record are explained. Finally the programming command of aforementioned string functions in COBOL. PL/1 are described.