第5章第2讲选择结构的基本形式

#include "stdio.h"

main()
{
    int score; 
    scanf("%d",&score);  
    if(score>=60) 
        printf("C语言成绩及格!\n");
}

#include "stdio.h"

main()
{

    int a,b,t; 
    scanf("%d%d",&a,&b); 
    if(a>b) 
    {
        t=a;     a=b;     b=t;  
    }
    printf("a=%d,b=%d\n",a,b); 

}

#include "stdio.h"

main()
{

    int n; 
    scanf("%d",&n); 
    if(n%2==0) 
       printf("该数是偶数!\n");
    else 
       printf("该数是奇数!\n");
}

#include "stdio.h"

main()
{
    int pwd; 
    scanf("%d",&pwd); 
    if(pwd==123456 ) 
       printf(“密码正确，登录成功!\n"); 
    else 
       printf("密码错误，无法登录!\n");

}

#include "stdio.h"

main()
{
    float Amount,ActualAmount; 
    scanf("%f",&Amount); 
    if(Amount>=10000)
           ActualAmount=Amount*0.5;
    else if(Amount>=8000)
           ActualAmount=Amount*0.6;
    else if(Amount>=5000)
           ActualAmount=Amount*0.7;
    else if(Amount>=3000)
           ActualAmount=Amount*0.8;
    else if(Amount>=1000)
           ActualAmount=Amount*0.9;
    else 
           ActualAmount=Amount;
    printf("付款:%f元\n",ActualAmount); 
}

#include "stdio.h"

main()
{

    int x,y;  
    scanf("%d%d",&x,&y); 
    if(x>0)
        if(y>0)
            printf("该点属于第一象限!\n")
        else
            printf("该点属于第四象限!\n");
    else
        if(y>0)
            printf("该点属于第二象限!\n");
        else
            printf("该点属于第三象限!\n");
}

#include "stdio.h"

main()
{
    int score,temp;
    char grade;
    scanf("%d",&score); 
    temp=score/10; 
    switch(temp)
    {    case 10: 
         case 9:grade='A';break;
         case 8:grade='B';break; 
         case 7:grade='C';break;
         case 6:grade='D';break;
         case 5: case 4: case 3:
         case 2: case 1: case 0:grade='E'; 
    }
    printf("五级制级别为:%c\n",grade);  

}