if statement

 

C

语言

类型的支持

动态内存管理

错误处理

程序实用工具

日期和时间工具

字符串库

算法

数值计算

输入/输出的支持

本地化的支持

线程的支持 （C11）

原子操作 （C11）

 

C语言编写

大会的主题 Original: General topics The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
预处理器
评论
关键字
ASCII表
转义序列
C
流量控制 Original: Flow control The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
条件执行语句 Original: Conditional execution statements The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
if statement	switch statement
迭代语句 Original: Iteration statements The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
for loop	while loop do-while loop
跳转语句 Original: Jump statements The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
continue statement break statement	goto statement return statement
功能 Original: Functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
函数声明
的历史。内嵌说明
类型 Original: Types The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
基本类型 指针类型 复合类型 枚举类型	联合类型 函数类型
规范 Original: Specifiers The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
CV符
存储类说明
alignas说明 （C99）
常 Original: Literals The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
整数文字 字符文字 浮点文字	字符串文字 布尔文字（C99）
表达式 Original: Expressions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
为了评价
其他运营商
运营商
运算符的优先级
实用工具 Original: Utilities The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
typedef declaration
属性 （C99）
转换
杂项 Original: Miscellaneous The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
内联汇编

 

有条件地执行代码

Original:

Conditionally executes code.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

只有在一定条件下是存在的，需要执行其中的代码使用.

Original:

Used where code needs to be executed only if some condition is present.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

语法

if ( expression ) statement_true
if ( expression ) statement_true else statement_false

解释

expression是一个表达式，转换为bool.

Original:

expression shall be an expression, convertible to bool.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

如果计算结果为true，控制被传递到statement_true，statement_false（如果有的话）不执行.

Original:

If it evaluates to true, control is passed to statement_true, statement_false (if present) is not executed.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

否则，控制传递到statement_falsestatement_true还没有执行.

Original:

Otherwise, control is passed to statement_false, statement_true is not executed.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

关键字

if, else

为例

#include <stdio.h>
 
int main()
{
    int i = 2;
    if (i > 2) {
        printf("first is true\n");
    } else {
        printf("first is false\n");
    }
 
    i = 3;
    if (i == 3) printf("i == 3\n");
 
    if (i != 3) printf("i != 3\n");
    else        printf("i != 3 is false\n");
}

Output:

first is false
i == 3
i != 3 is false