How to check a character value in C

Feb 18, 2020

Learn how to check a character value in C using the ctype.h functions like isalpha(), isdigit(), isspace(), islower(), and isupper() to test a char.

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When working in C, we can use the ctype.h standard library set of functions to check the value of a char type variable.

We have access to several useful checks:

isalnum() checks if a character is alphanumeric
isalpha() checks if a character is alphabetic
iscntrl() checks if a character is a control character
isdigit() checks if a character is a digit
isgraph() checks if a character is a printable ASCII character (but not a space)
islower() checks if a character is lowercase
isprint() checks if a character is a printable ASCII character
ispunct() checks if a character is a punctuation character (a printable char, not a space, not alphanumeric)
isspace() checks if a character is a whitespace character (see more later)
isupper() checks if a character is uppercase
isxdigit() checks if a character is an hexadecimal digit (0-F)

I mentioned that isspace() checks if a character is a whitespace character. What is a whitespace character?

Tagged: C · All topics

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