C99 boolean data type?

Include <stdbool.h> header

#include <stdbool.h>int main(void){  bool b = false;}

Macros true and false expand to 1 and 0 respectively.

Section 7.16 Boolean type and values < stdbool.h >

• 1 The header <stdbool.h> defines four macros.
• 2 The macro
  • bool expands to _Bool.
• 3 The remaining three macros are suitable for use in #if preprocessing directives. They are
  • true : which expands to the integer constant 1,
  • false: which expands to the integer constant 0, and
  • __bool_true_false_are_defined which expands to the integer constant 1.
• 4 Notwithstanding the provisions of 7.1.3, a program may undefine and perhaps then redefine the macros bool, true, and false.

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extracted and quoted here for convenient reference:-

usage of new keywords in c99

_Bool: C99's boolean type. Using _Bool directly is only recommended if you're maintaining legacy code that already defines macros for bool, true, or false. Otherwise, those macros are standardized in the <stdbool.h> header. Include that header and you can use bool just like you would in C++.

#include <stdio.h>#include <stdbool.h>int main ( void ){  bool b = true;  if ( b )    printf ( "Yes\n" );  else    printf ( "No\n" );  return 0;}