一个简单的函数声明和调用

//
//  main.m
//  HeloObjectiveC
//
//  Created by wb on 14-9-13.
//  Copyright (c) 2014年 wb. All rights reserved.
//

#import <Foundation/Foundation.h>


BOOL areIntsDifferent (int thing1, int thing2)  //
{
    if (thing1==thing2)
    {
        return  (NO);
    }
    else
        return (YES);

}

NSString *Boolstring(BOOL yesno)  //字符型声明前面有*，表示字符串属于指针类型，char类型相同，赋值时使用@表示地址指针调用
{
    if (yesno==NO)
    {
        return  (@"NO");
    }
    else
    {
        return (@"Yes");
    }
}


int main(int argc, const char * argv[])
{

    BOOL areTheDifferent;                                                     //BOOL类型，值为YES和NO，不能用数值来表示
    areTheDifferent=areIntsDifferent (5,5);
    
    NSLog(@"are %d and %d different? %@" ,5,5,Boolstring(areTheDifferent));    //格式化数字%d ,格式化文本%@ 
   
    areTheDifferent=areIntsDifferent (23,42);

    
    NSLog (@"are %d and %d different?  %@ " ,23,42,Boolstring(areTheDifferent));
    return 0;
}