C语言函数

#include <stdio.h>
int main()
{
    int count1 =1;
    do{
        int count2 =0;
        ++count2;

        printf("
count1=%d count2=%d",count1,count2);
        count1++;
    }while (count1<=8);
    
    printf("
 count1=%d
",count1);
    return 0;
}

不等价于下面这个，尽管两个输出一样

#include <stdio.h>
int main()
{
    int count1 =1;
    do{
        int count2 =0;
        ++count2;
        printf("
count1=%d count2=%d",count1,count2);
        
    }while (++count1<=8);
    
    printf("
 count1=%d
",count1);
    return 0;

}

 详情见下面这个例子

#include <stdio.h>
int main(void)
{
    int count= 0;
    do{
        int count =0;
        ++count ;
        printf("
 count=%d",count );
    }
    while (++count<=8);                                                
    
    printf("
 count =%d
",count );
    return 0;
}    

/*

count=0

  count=0
  count=1 dayin
  count=1<=8

  count=0
  count=1 dayin
 !! count=2<=8

...

  count=0
  count=1  dayin
  count=8<=8 

  count=0
  count=1  dayin
  count=9   wo tiao

  count=9  shuchu



关键在于while 中的count 和do while 里面的不是一回事，while 使用的是那个外面的，do{}的count出了括号就死了
作用域就是这么回事，以大括号为界限，出来就死。   生存期就是，就活一轮，下一轮就重生

*/

#include <stdio.h>
float average(float x ,float y)
{
    return (x+y)/2.0f;
}

int main (void)
{
    float value1=0.0F;
    float value2=0.0F;
    float value3=0.0F;
    
    
    printf("Enter two floating-point values separated by blanks:
");
    scanf("%f %f",&value1,&value2);
    value3=average (value1,value2);
    printf("
 The average is:%f
",value3);
    return 0;
    
}/*  函数调用例子*/

#include <stdio.h>
float average(float x  ,float y);/* 也可以写做  float average (float ,float);    */

int main (void)
{
    float value1=0.0F;
    float value2=0.0F;
    float value3=0.0F;
    
    
    printf("Enter two floating-point values separated by blanks:
");
    scanf("%f %f",&value1,&value2);
    value3=average (value1,value2);
    printf("
 The average is:%f
",value3);
    return 0;
    
}

float average(float x ,float y)
{
    return (x+y)/2.0f;
}

/*不使用指针和使用指针的比较 
	相当于制表符移动8个光标，等价于一个Tab键

不使用指针改变的不多

*/
#include <stdio.h>
int change(int number);

int main (void)
{
    int number =10;
    int result=0;
    result=change(number);
    printf("
 In main ,result=%d,	number=%d",result,number);
    return  0;
}

int change(int number)
{
    number = 2*number;
    printf("
 In function change ,number =%d
",number);
    return number;
}

/*     使用指针，把number也改变了，因为指针就是他的地址，地址变了，啥都变了，把指针作为变元，若要对一个数进行操作，那么对他的指针操作，把他的指针当做变元，改变的他的指针才可以真正的改变这个数 */

#include <stdio.h>
int change (int *pnumber);
int main(void)
{
    int number=10;
    int * pnumber=&number;
    int result =0;
    
    result =change(pnumber);
    printf("
 In main, result =%d	 number=%d",result ,number );
    return 0;
    
}

    int change(int *pnumber)
    {
        *pnumber*=2;
        printf("
 In function change ,*pnumber=%d
",*pnumber);
        return *pnumber ;
        
    }