C Reference Control Character Test: iscntrl()

The iscntrl() function returns a non-zero if its argument is a control character. If there is no control character encountered, then zero is returned.

isalpha() source code example:

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C Reference Alphabetic Test: isalpha()

The function isalpha() returns a non-zero if its argument is a letter of the alphabet. If it is not a letter of the alphabet, then zero is returned.

isalpha() source code example:

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C Reference Alphanumeric Test: isalnum()

The function isalnum() returns a non-zero if its argument is a letter of the alphabet or a numeric digit. If it is not letter of the alphabet or a numeric digit, then zero is returned.

isalnum() source code example:

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