Characters that cannot be printed on the screen are known as control characters. For example, backspace, Escape, newline etc.
The iscntrl()
function checks whether a character (passed to the function) is a control character or not. If the character passed is a control character, it returns a non-zero integer. If not, it returns 0
.
This function is defined in ctype.h header file.
Function Prototype of iscntrl()
int iscntrl(int argument);
The isntrl() function takes a single argument and returns an integer.
When character is passed as an argument, corresponding ASCII value of the character is passed instead of that character itself.
Example #1: Check control character
#include <stdio.h>
#include <ctype.h>
int main()
{
char c;
int result;
c = 'Q';
result = iscntrl(c);
printf("When %c is passed to iscntrl() = %d\n", c, result);
c = '\n';
result = iscntrl(c);
printf("When %c is passed to iscntrl() = %d", c, result);
return 0;
}
Output
When Q is passed to iscntrl() = 0 When is passed to iscntrl() = 1
Example #2: Print ASCII value of All Control characters
#include <stdio.h>
#include <ctype.h>
int main()
{
int i;
printf("The ASCII value of all control characters are:\n");
for (i=0; i<=127; ++i)
{
if (iscntrl(i)!=0)
printf("%d ", i);
}
return 0;
}
Output
The ASCII value of all control characters are: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 127