C ctype isalnum() Function
Example
Check if a character is alphanumeric (a letter or number):
char c = 'A';
if (isalnum(c)) {
printf("%c is alphanumeric", c);
} else {
printf("%c is not alphanumeric", c);
}Definition and Usage
The isalnum() function returns a non-zero
value (equivalent to boolean true) if a character is alphanumeric,
meaning an alphabet letter (a-z) or a number (0-9).
Example of characters that are not alphanumeric: (space)!#%&? etc.
The isalnum() function is defined in the <ctype.h> header file.
Syntax
int isalnum(int c);Parameter Values
| Parameter | Description |
|---|---|
| c | Required. The ASCII value of a character or an actual character |
Technical Details
| Returns: | An int value which is non-zero (equivalent to boolean
true)
if the character is alphanumeric.Otherwise it returns 0 (equivalent to boolean false). |
|---|
More Examples
Example
Check different characters:
void checkNum(char c) {
if (isalnum(c)) {
printf("%c is alphanumeric\n", c);
} else {
printf("%c is not alphanumeric\n", c);
}
}
int main() {
char char1 = 'B';
char char2 = 'X';
char char3 = '+';
checkNum(char1);
checkNum(char2);
checkNum(char3);
return 0;
}