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快速入门——库的操作
查看>>
mysql快速复制一张表的内容,并添加新内容到另一张表中
查看>>
mysql快速查询表的结构和注释,字段等信息
查看>>
mysql怎么删除临时表里的数据_MySQL中关于临时表的一些基本使用方法
查看>>
mysql性能优化
查看>>
mysql性能优化学习笔记-存储引擎
查看>>
MySQL性能优化必备25条
查看>>
Mysql性能优化(1):SQL的执行过程
查看>>
Mysql性能优化(2):数据库索引
查看>>
Mysql性能优化(3):分析执行计划
查看>>
Mysql性能优化(4):优化的注意事项
查看>>
Mysql性能优化(5):主从同步原理与实现
查看>>
Mysql性能优化(6):读写分离
查看>>
MySQL性能优化(八)--
查看>>
MySQL性能测试及调优中的死锁处理方法
查看>>
mysql性能测试工具选择 mysql软件测试
查看>>
mysql恢复root密码
查看>>
Mysql悲观锁
查看>>
MySQL慢查询-开启慢查询
查看>>
MySQL慢查询分析和性能优化的方法和技巧
查看>>