The following functions return ≠ 0, if character c belongs to the specified character set; 0 otherwise.
#include ctype.h>
#(c) &# &set isalnumLetter or Digit isalphaLetter isasciiASCII character (Codes: 0…0177) iscntrlControl character (Codes: 0…037, 0177) isdigitDigit isgraphPrintable character except space islowerLowercase letter isprintPrintable character ispunctPunctuation char. (not letter, digit or control) isspaceSpace, Tab, CR, NL, VT, FF or BS isupperUppercase letter isxdigitHexadecimal digit iswhitesame as ispace() isodigitOctal digit iscymfCharacter starting a C identifier iscymCharacters continuing a C identifier
Character conversion functions
#(c) &# &Meaning toupperConvert to uppercase letter _toupperConvert to uppercase letter (macro) tolowerConvert to lowercase letter _tolowerConvert to lowercase letter (macro) tointConvert digit to integer