iscntrl : char functions « Data Types « C++ Tutorial

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2. Data Types
3. char functions

#include <iostream>
using std::cout;
using std::endl;

#include <cctype>
using std::iscntrl;
using std::isgraph;
using std::isprint;
using std::ispunct;
using std::isspace;

int main()
{
   cout << "\nAccording to iscntrl:\nNewline " 
      << ( iscntrl( '\n' ) ? "is a" : "is not a" )
      << " control character\n"
      << ( iscntrl( '$' ) ? "$ is a" : "$ is not a" )
      << " control character\n";
   return 0;
}

According to iscntrl:
Newline is a control character
$ is not a control character