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:


int main()
	char a;
	scanf( "%c", &a );
	if( isalnum(a) )
		printf( "This is an alphanumeric character: %c\n", a );
		printf( "This is NOT an alphanumeric character: %c\n", a );
	return 0;

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