C – iscntrl() function – Learn C, C++ Programming

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iscntrl( ) function in C language checks whether given character is control character or not. Syntax for iscntrl( ) function is given below.

int iscntrl( int x );

Control characters in C language are ‘a’ ( alert ), ‘b’ ( backspace ), ‘f’ ( form feed ), ‘n’ ( new line ), ‘r’ ( carriage return ), ‘t’ ( horizondal tab), ‘v’ ( vertical tab) and ‘’ ( null ).

Note:

‘a’ – Alert character is used to produce visible or audible alert in output.
‘b’ -It is used to move the position of pointer to one position back in current line.
‘f’ – form feed character is used to start a new page.
‘n’- new line character moves to the next line from the current line.
‘r’ – carriage return is used to move the position to the beginning of current line.
‘t’ – It is used to move the pointer to the horizontal tab space in current line.

Example program for iscntrl() function in C:

#include <stdio.h>

int main()
{
   char ch[5] ="abca";
   int i = 0;
while(1)
   {
      if(iscntrl(ch[i]))
      {
          printf ( "control character is found at " 
                    "%dth positionn", i+1); 
         break;
      }
      i++;
   }   
   return 0;
}

Output:

control character is found at 4th position

Other Int, Char validation functions in C language:

All “int, char validation functions” used in C language are given below. “ctype.h” header files support all these functions in C language.
Click on each function name below for detail description and example programs.

S.no	Function	Description
1	isalpha()	checks whether character is alphabetic
2	isdigit()	checks whether character is digit
3	isalnum()	checks whether character is alphanumeric
4	isspace()	checks whether character is space
5	islower()	checks whether character is lower case
6	isupper()	checks whether character is upper case
7	isxdigit()	checks whether character is hexadecimal
8	iscntrl()	checks whether character is a control character
9	isprint()	checks whether character is a printable character
10	ispunct()	checks whether character is a punctuation
11	isgraph()	checks whether character is a graphical character
12	tolower()	checks whether character is alphabetic & converts to lower case
13	toupper()	checks whether character is alphabetic & converts to upper case