Is there any standard way to use boolean? because my code is giving an error

#include<stdio.h>
boolean ch(char x)
{

if(x>=48&&x<=57)
return 1;
else
return 0;

}
main()
{

if(!ch('t'))
printf("it's a character");

}

error:

cha.c:3: error: boolean' does not name a type cha.c: In functionint 开发者_开发知识库main()': cha.c:15: error: `ch' was not declared in this scope

Yes, the C99 standard has introduced the _Bool type

Update

Apparently <stdbool.h> also includes the prettier bool type in addition to the true and false macros. Updated code to reflect this.

#include <stdio.h>
#include <stdbool.h>

bool ch(int);

int main(void)
{
    if(!ch('t'))
        printf("it's a character\n");
    return 0;
}

bool ch(int x)
{
    if (x >= 48 && x <= 57)
        return true;
    else
        return false;
}

Click this link to see the compiled code's output

And googling wins again

Boolean Expressions and Variables : What is the right type to use for Boolean values in C? Is there a standard type? Should I use #defines or enums for the true and false values?

Unless I'm crazy, C doesn't have a boolean type. Change the return type of ch to int

Also, post your error message.

C does not have a built-in boolean type. A bool type is available in the stdbool.h header in the standard library in C99.

http://en.wikipedia.org/wiki/Stdbool.h

You've got more problems than just the type, however. if(x>=48&&x<=57) doesn't mean what you think it does, and your printf is going to give you unexpected results too.

You're going to need these characters: "(())\n" and a bunch of whitespace.

Sorry to be a little cryptic but this looks like a homework problem.

The conditional statement if (boolean_expression) return true; else return false; can always be replaced by return boolean_expression; which I find a lot more readable.

Also, your naming is terrible, what does ch stand for? Since 48 is 0 and 47 is 9, a better name would probably be is_digit or something. (And, as others have noted, C89 does not have a boolean type.)

int is_digit(char c)
{
    return (c >= '0') && (c <= '9');
}

The parenthesis are optional, but I think they make the code more readable.

And what do you mean by the output "It's a character" in main? Every char is a character, duh :)