我想把以下几个程序合并到一个程序中执行 ，输入1则执行加法，2执行减法，3执行乘法，4执行除法（各位也可以给出更简单的表示方法）
请高手多多指教，万分感谢
以下是求和的程序：
#include "stdio.h"                            
void main()                                    
{
    float a,b,c;                            
    scanf("%f%f",&a,&b);                
    c=a+b;                                
    printf(" %f\n",c);                            
}
以下是求差的程序：
#include "stdio.h"                            
void main()                                    
{
    float a,b,c;                            
    scanf("%f%f",&a,&b);                
    c=a-b;                                
    printf(" %f\n",c);                            
}
以下是求积的程序：
#include "stdio.h"                            
void main()                                    
{
    float a,b,c;                            
    scanf("%f%f",&a,&b);                
    c=a*b;                                
    printf(" %f\n",c);                            
}
以下是求商的程序：
#include "stdio.h"                            
void main()                                    
{
    float a,b,c;                            
    scanf("%f%f",&a,&b);                
    c=a/b;                                
    printf(" %f\n",c);                            
}

#include "stdio.h"                            
void main()                                    
{
    float a,b,c,d,e,f;int n;  
    printf("输入a和b的值\n");
    scanf("%f%f",&a,&b); 
    printf("请输入数字，输入1则执行加法，2执行减法，3执行乘法，4执行除法\n");
    scanf("%d",&n);
    if(n==1)
    {
        c=a+b;                                
    printf(" %f\n",c);
    }
    else if(n==2)
    {

        d=a-b;printf("%f\n",d);
    }
    else if(n==3)
    {
    
        e=a*b;
        printf("%f\n",e);
    }
    else if(n==4)
    {
    f=a/b;printf("%f\n",f);
    }
}

当然，也可以利用函数来实现。

可以用switch语句来实现。

谢谢大家的涌跃回答！

#include "stdio.h"  
int main()
{
    float a,b,c;
    int k;
    printf("请输入a,b的值\n");
    scanf("%f %f",&a,&b);
    printf("a=%f,b=%f\n",a,b);
    printf("请输入k的值\n");
    scanf("%d",&k);
    printf("k=%d\n",k);
    switch(k)
    {
    case 1:c=a+b;break;
    case 2:c=a-b;break;
    case 3:c=a*b;break;
    case 4:c=a/b;
    }
    printf("c=%f\n",c);
    getchar();
    return 0;
}

#include<stdio.h>
int main()
{
    double a,b,c=0;
    int n;
    scanf("%lf%lf%d",&a,&b,&n);
    switch(n)
    {
        case 1:c = a+b ;break;
        case 2:c = a-b ;break;
        case 3:c = a*b ;break;
        case 4:if(fabs(b-0)>1e-6)c = a/b ;break;
    }
    printf("%lf\n",c);
    return 0 ;
}

那用IF语句也可以啊，还有goto语句也没问题的

#include <stdio.h>                           
main()                                    
{
    float a,b,c;
    int n;
    A:
    {
    scanf ("%d",&n);
    scanf("%f %f",&a,&b);
    while(n==1)                           
      {
          c=a+b;                                
          printf(" %f\n",c);break;}
    while(n==2)                              
      {
          c=a-b;                                
          printf(" %f\n",c);break;}
    while(n==3)                                
      {
          c=a*b;                                
          printf(" %f\n",c);break;}
    while(n==4)                              
      {
          c=a/b;                                
          printf(" %f\n",c);break;}}
    goto A;                           
}