C語言設計實數四則運算運用MAKEFILE，程式如下

#include<stdio.h>

#include<stdlib.h>

#include<math.h>void jiafa()

{

double i,j;

printf("請輸入兩個實數:");

scanf("%lf %lf",&i,&j);

printf("%5.2f+%5.2f=%5.2f\n",i,j,i+j);

}void jianfa()

{

double i,j;

printf("請輸入兩個實數:");

scanf("%lf %lf",&i,&j);

printf("%5.2f-%5.2f=%5.2f\n",i,j,i-j);

}

void chengfa()

{

double i,j;

printf("請輸入兩個實數:");

scanf("%lf %lf",&i,&j);

printf("%5.2f*%5.2f=%5.2f\n",i,j,i*j);

}

void chufa()

{

double i,j;

printf("請輸入兩個實數:");

scanf("%lf %lf",&i,&j);

printf("%5.2f/%5.2f=%5.2f\n",i,j,(double)i/j);

}void main()

{

int shuru=0;

char x;

system("pause");

system("cls");

while (1)

{

printf("你需要做什麼題型計算？請選擇:+(輸入1) - (輸入2) *(輸入3) /(輸入4)\n");

if(shuru==0)

scanf("%c",&x);

switch(x)

{

case "1": jiafa();break;

case "2": jianfa();break;

case "3": chengfa();break;

case "4": chufa();break;

default : printf("輸入錯誤，請重新輸入");

}

printf("請輸入數字選擇：\n1.繼續\n2.重新選擇題型\n3.結束\n");

scanf("%d",&shuru);

if(shuru==1) shuru=1;

if(shuru==2) {shuru=0;getchar();}

if(shuru==3) break;

}

}