博客
关于我
Variables and Types 变量和类型
阅读量:192 次
发布时间:2019-02-28

本文共 2533 字,大约阅读时间需要 8 分钟。

 


Data types   数据类型

C has several types of variables, but there are a few(一些) basic types:

  • Integers (整型)- whole numbers which can be either positive(正数) or negative(负数)(要么...要么). Defined using charintshortlong or long long.

  • Unsigned integers(无符号整型) - whole numbers which can only be positive. Defined  using unsigned char,  unsigned int,   unsigned shortunsigned long or unsigned long long.

  • Floating point numbers(浮点数) - real numbers实数 (numbers with fractions). Defined using float and double.

  • Structures(结构体) - will be explained later, in the Structures section.(稍后将在“结构”一节中解释。)
     

The different types of variables define their bounds(界限). A char can range(范围) only from -128 to 127, whereas a long can range from -2,147,483,648 to 2,147,483,647 (long and other numeric data types(数字数据类型) may have another range on different computers, for example - from –9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 on 64-bit computer).

Note that C does not have a boolean type(布尔类型). Usually, it is defined using the following notation(符号):

#define BOOL char#define FALSE 0#define TRUE 1

C uses arrays of characters(字符数组) to define strings(字符串), and will be explained in the Strings section.

Defining variables  定义变量

For numbers(数字), we will usually use the type int, which an integer in the size of a "word"(字)the default number size of the machine which your program is compiled on. On most computers today, it is a 32-bit number, which means the number can range from -2,147,483,648 to 2,147,483,647.

To define the variables foo and bar, we need to use the following syntax(语法):

int foo;int bar = 1;

The variable foo can be used, but since we did not initialize(初始化) it, we don't know what's in it. The variable bar contains(包含) the number 1.

Now, we can do some math. Assuming(假设) abcd, and e are variables, we can simply use plus, minus and multiplication(乘法) operators in the following notation, and assign(分配,赋值) a new value to a:

int a = 0, b = 1, c = 2, d = 3, e = 4;a = b - c + d * e;printf("%d", a); /* will print 1-2+3*4 = 11 */

Exercise

In the next exercise, you will need to create a program which prints out the sum of the numbers ab, and c.

原:

#include 
int main() { int a = 3; float b = 4.5; double c = 5.25; float sum; /* Your code goes here */ printf("The sum of a, b, and c is %f.", sum); return 0;}

 

改:

#include 
int main() { int a = 3; float b = 4.5; double c = 5.25; float sum; /* Your code goes here */ sum = a + b + c ; printf("The sum of a, b, and c is %f.", sum); return 0;}

 

 

转载地址:http://fnii.baihongyu.com/

你可能感兴趣的文章
mysql 数据库中 count(*),count(1),count(列名)区别和效率问题
查看>>
mysql 数据库备份及ibdata1的瘦身
查看>>
MySQL 数据库备份种类以及常用备份工具汇总
查看>>
mysql 数据库存储引擎怎么选择?快来看看性能测试吧
查看>>
MySQL 数据库操作指南:学习如何使用 Python 进行增删改查操作
查看>>
MySQL 数据库的高可用性分析
查看>>
MySQL 数据库设计总结
查看>>
Mysql 数据库重置ID排序
查看>>
Mysql 数据类型一日期
查看>>
MySQL 数据类型和属性
查看>>
mysql 敲错命令 想取消怎么办?
查看>>
Mysql 整形列的字节与存储范围
查看>>
mysql 断电数据损坏,无法启动
查看>>
MySQL 日期时间类型的选择
查看>>
Mysql 时间操作(当天,昨天,7天,30天,半年,全年,季度)
查看>>
MySQL 是如何加锁的?
查看>>
MySQL 是怎样运行的 - InnoDB数据页结构
查看>>
mysql 更新子表_mysql 在update中实现子查询的方式
查看>>
MySQL 有什么优点?
查看>>
mysql 权限整理记录
查看>>