示例程序//一个对长跑运动员有用的程序#include<stdio.h>#define S_PER_H  3600#define S_PER_M  60#define S_PER_K   0.62137int main(void){    double distk,distm;//跑过的路程，公里、英里    double  rate;//以英里/每小时的单位平均速度    int min,sec;//跑步用的分钟数和秒钟数    int time;//用秒表示跑步时间    double mtime;//跑完以英里所用的时间，以秒计算    int mmin,msec;//跑完一英里所用的时间，以分钟和秒计算。    printf("This program converts your time for a metric race\n");    printf("to a time foe running a mile and to your average\n");    printf("speed in miles per hour.\n");    printf("please enter ,in kilometers,the distance run.\n");    scanf("%lf",&distk);//表示读取一个double类型的数值    printf("Next enter the time in minutes and distance and seconds.\n");    printf("Begin by entering the minutes.\n");    scanf("%d",&min);    printf("Now enter the seconds.\n");    scanf("%d",&sec);    //把时间转化为全部用秒表示    time=S_PER_M*min+sec;    //把公里转化为英里    distm=S_PER_K*distk;    //英里/秒*秒/小时=英里/小时    rate=distm/time*S_PER_H;    //时间/距离=跑完每英里用的时间    mtime=(double)time/distm;    mmin=(int)mtime/S_PER_M;//求出分钟数    msec=(int)mtime%S_PER_M;//求出剩余的秒数    printf("you can %1.2f km(%1.2f miles) in %d min.%d sec.\n",        //如果(%1.2f miles)变成了(%1.2 miles)会怎么样？        distk,distm,min,sec);    printf("That pacecorresponds to running a mile in %d min.",min);    printf("%d sec.\nYour average speed was %1.2f mph.\n",msec,rate);    return 0;}

关于棋盘麦粒的问题//关于棋盘麦粒的问题#include<stdio.h>#define SQUARES  64#define CROP  1E15int main(void){    double current,total;    int count=1;//棋盘的格子数    printf("square grains added    total grains   fraction of\n");    printf("                                      US total\n");    total=current=1.0;//开始时是1粒      //total为麦子的总数    //current为当前棋盘格子麦子的数量    printf("%4d %13.2e %12.2e %15.2e\n",count,current,total,total/CROP);    while(count<SQUARES)    {        count=count+1;        current=2.0*current;            //下个方格的粒数加倍        total=total+current;//更新总数        printf("%4d %13.2e %12.2e %15.2e\n",count,current,total,total/CROP);    }    printf("That‘s all.\n");    return 0;}

除法运算符///除法运算符/#include<stdio.h>int main(void){    printf("integer division 5/4 is %d \n",5/4);//整数除法的小树部分被丢弃    printf("integer division 6/3 is %d \n",6/3);    printf("integer division 7/4 is %d \n",7/4);    printf("floating division 7.0/4. is %.2f \n",7.0/4.);    printf("mixed(混合类型） division 7.0/4 is %.2f \n",7.0/4); //4自动转换成float类型    return 0;}

把秒转换成分钟和秒//把秒转换成分钟和秒#include<stdio.h>#define SEC_PER_MIN  60int main(void){    int sec,min,left;    printf("convert seconds to minutes and seconds!\n");    printf("Enter the number of seconds (<=0) to quit):\n");    scanf("%d",&sec);//读入秒数    while(sec>0)    {        min=sec/SEC_PER_MIN;//截尾后得到的分钟数。        left=sec%SEC_PER_MIN;//剩下的秒数。        printf("%d seconds is %d minutes,%d seconds.\n",            sec,min,left);        printf("Enter next value(<=0 to quit):\n");        scanf("%d",&sec);    }    printf("Done!\n");    return 0;}

后缀和前缀#include<stdio.h>int main(void){    int a=1,b=1;    int aplus,plusb;    aplus=a++;    plusb=++b;    printf("a aplus b plusb.\n");    printf("%ld %5d %5d %5d\n",a,aplus,b,plusb);    return 0;}//输出结果为 2 1 2 2//a++ 使用a的值之后 改变a.//++a 先改变a的值，然后使用a

四种类型的语句 //四种类型的语句#include<stdio.h>int main(void)            //求出前20个整数的和{    int count,sum;        //声明语句    count =0;             //赋值语句    sum=0;    while(count++<20)     //while        sum=sum+count;    //语句    printf("sum=%d\n",sum);//函数语句    return 0;}

定义一个有参数的函数//定义一个有参数的函数#include<stdio.h>void pound(int n);//函数声明（原型）int main(void){    int times=5;    char ch=‘!‘;    float f=6.0;    pound(times);//int 型参数    pound(ch);//char 参数自动转换成int类型    pound((int)f);    return 0;}void  pound(int n)//说明该函数接受一个int型参数{    while(n-->0)        printf("#");    printf("\n");}