C语言及程序设计初步例程-8 数值数据类型及表示

来源：互联网发布：java io分类编辑：程序博客网时间：2024/06/05 09:12

贺老师教学链接 C语言及程序设计初步本课讲解

例：程序中的数据类型、常量、变量

#include <stdio.h>int main( ){    float f,m;    printf("length in feet: ");    scanf("%f", &f);    m = f / 3.28;    printf("equal to %f meters.\n", m);    return 0;}

列出当前系统中各种类型数据占用的字节数

#include <stdio.h>int main( ){    printf("Size of int is: %d\n",sizeof(int));    printf("Size of short int is: %d\n",sizeof(short));    printf("Size of long int is: %d\n",sizeof(long));    printf("Size of unsigned int is: %d\n",sizeof(unsigned int));    printf("Size of float is: %d\n",sizeof(float));    printf("Size of double is: %d\n",sizeof(double));    printf("Size of long double is: %d\n",sizeof(long double));    printf("Size of char is: %d\n",sizeof(char));    return 0;}

程序中慎重直接使用常量——用符号常量替代

#include <stdio.h>#define PI 3.1415926  //定义符号常量int main ( ){  float r,l,s,sq,vq;  printf("please enter r,h:");  scanf("%f %f"), &r, &h);  l=2* PI *r;  s=r*r* PI;  sq=4* PI *r*r;  ……}

对比

/*不用符号常量的程序，注意若的错误*/#include <stdio.h>int main ( ){  float r,l,s,sq,vq;  printf("please enter r,h:");  scanf("%f %f"), &r, &h);  l=2* 3.1415926 *r;  s=r*r* 3.1415926;  sq=4* 3.1445926 *r*r;  ……}

再品符号常量

//程序的问题：可读性差、难维护#include <stdio.h>int main ( ){    int n, age, total;    scanf("%d %d", &age, &n);    if(age<30)     {        total=n*30;        printf("total=%d\n",total);    }    else    {        printf("done!\n");    }    return 0;}

改进的代码：

#include <stdio.h>#define PRICE 30  //代表固定的单价#define AGE 30    //代表年龄int main ( ){    int n, age, total;    scanf("%d %d", &age, &n);    if(age<AGE)  //30岁以下的才可以买    {        total=n*PRICE;        printf("total=%d\n",total);    }    else    {        printf("done!\n");    }    return 0;}

2 0