C <ctype.h>

The C <ctype.h> header file declares a set of functions to classify (and transform) individual characters. For example, isupper() checks whether a character is uppercase or not.

checks alphanumeric character

checks whether a character is an alphabet or not

checks control character

checks numeric character

checks graphic character

checks lowercase alphabet

checks printable character

checks punctuation

check white-space character

checks uppercase alphabet

checks hexadecimal digit character

converts alphabet to lowercase

converts to uppercase alphabet