The default value of BOOL variable is NO. You can use the following code to find the value of BOOL variable. 

//
//  PrintBoolean.h
//  DataTypes
// 

#import <Foundation/Foundation.h>

@interface PrintBoolean : NSObject {

    BOOL mBool;

}

-(void) print;

@end

and the code of the implementation class will be:

//
//  PrintBoolean.m
//  DataTypes
// 

#import "PrintBoolean.h"

@implementation PrintBoolean

-(void) print{

NSLog(@"The value of the bool is %@\n", (mBool ? @"YES" : @"NO"));

}

@end

Related Tags for Printing Boolean values with NSLog function: