C 语言运算符完全指南：算术、关系、逻辑、位运算等

C 语言运算符完全指南

本教程通过示例全面讲解 C 语言算术、自增自减、赋值、关系、逻辑、位运算及其他运算符的用法与优先级。

视频：C 语言算术运算符

运算符是作用于值或变量的符号。例如：+ 执行加法。

C 语言提供丰富运算符执行各种操作。

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C 算术运算符

对数值（常量和变量）执行加减乘除等数学运算。

运算符	含义
+	加法或一元正号
-	减法或一元负号
*	乘法
/	除法
%	取模（除法余数）

示例 1：算术运算符

// 算术运算符演示
#include <stdio.h>
int main() {
    int a = 9, b = 4, c;
    c = a + b; printf("a+b = %d \n", c);
    c = a - b; printf("a-b = %d \n", c);
    c = a * b; printf("a*b = %d \n", c);
    c = a / b; printf("a/b = %d \n", c);
    c = a % b; printf("Remainder when a divided by b = %d \n", c);
    return 0;
}

输出

a+b = 13
a-b = 5
a*b = 36
a/b = 2
Remainder when a divided by b = 1

+、-、* 符合预期。9/4 数学上为 2.25，但程序输出 2，因两操作数均为 int，编译器截断小数部分。

% 仅用于整数。若 a=5.0、b=2.0、c=5、d=2，则：

// 任一操作数为浮点数
a/b = 2.5
a/d = 2.5
c/b = 2.5
// 两操作数均为整数
c/d = 2

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C 自增与自减运算符

++ 增加 1，-- 减少 1，均为一元运算符。

示例 2：自增自减运算符

// 自增自减演示
#include <stdio.h>
int main() {
    int a = 10, b = 100;
    float c = 10.5, d = 100.5;
    printf("++a = %d \n", ++a);
    printf("--b = %d \n", --b);
    printf("++c = %f \n", ++c);
    printf("--d = %f \n", --d);
    return 0;
}

输出

++a = 11
--b = 99
++c = 11.500000
--d = 99.500000

此处为前缀用法。也可作后缀 a++、a--，后缀版本先使用值再修改。

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C 赋值运算符

最常用赋值运算符为 =。

运算符	示例	等价于
=	a = b	a = b
+=	a += b	a = a+b
-=	a -= b	a = a-b
*=	a *= b	a = a*b
/=	a /= b	a = a/b
%=	a %= b	a = a%b

示例 3：赋值运算符

// 赋值运算符演示
#include <stdio.h>
int main() {
    int a = 5, c;
    c = a; printf("c = %d\n", c);   // 5
    c += a; printf("c = %d\n", c);  // 10
    c -= a; printf("c = %d\n", c);  // 5
    c *= a; printf("c = %d\n", c);  // 25
    c /= a; printf("c = %d\n", c);  // 5
    c %= a; printf("c = %d\n", c);  // 0
    return 0;
}

输出

c = 5
c = 10
c = 5
c = 25
c = 5
c = 0

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C 关系运算符

检查两操作数关系，真返回 1，假返回 0。用于决策与循环。

运算符	含义	示例
==	等于	5 == 3 为 0
>	大于	5 > 3 为 1
<	小于	5 < 3 为 0
!=	不等于	5 != 3 为 1
>=	大于等于	5 >= 3 为 1
<=	小于等于	5 <= 3 为 0

示例 4：关系运算符

// 关系运算符演示
#include <stdio.h>
int main() {
    int a = 5, b = 5, c = 10;
    printf("%d == %d is %d \n", a, b, a == b);
    printf("%d == %d is %d \n", a, c, a == c);
    printf("%d > %d is %d \n", a, b, a > b);
    printf("%d > %d is %d \n", a, c, a > c);
    printf("%d < %d is %d \n", a, b, a < b);
    printf("%d < %d is %d \n", a, c, a < c);
    printf("%d != %d is %d \n", a, b, a != b);
    printf("%d != %d is %d \n", a, c, a != c);
    printf("%d >= %d is %d \n", a, b, a >= b);
    printf("%d >= %d is %d \n", a, c, a >= c);
    printf("%d <= %d is %d \n", a, b, a <= b);
    printf("%d <= %d is %d \n", a, c, a <= c);
    return 0;
}

输出

5 == 5 is 1
5 == 10 is 0
5 > 5 is 0
5 > 10 is 0
5 < 5 is 0
5 < 10 is 1
5 != 5 is 0
5 != 10 is 1
5 >= 5 is 1
5 >= 10 is 0
5 <= 5 is 1
5 <= 10 is 1

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C 逻辑运算符

包含逻辑运算符的表达式返回 0 或 1，常用于决策。

运算符	含义	示例
&&	逻辑与。全真才真	c=5,d=2 时 ((c==5) && (d>5)) 为 0
||	逻辑或。一真即真	c=5,d=2 时 ((c==5) || (d>5)) 为 1
!	逻辑非。操作数为 0 才真	c=5 时 !(c==5) 为 0

示例 5：逻辑运算符

// 逻辑运算符演示
#include <stdio.h>
int main() {
    int a = 5, b = 5, c = 10, result;
    result = (a == b) && (c > b);
    printf("(a == b) && (c > b) is %d \n", result);
    result = (a == b) && (c < b);
    printf("(a == b) && (c < b) is %d \n", result);
    result = (a == b) || (c < b);
    printf("(a == b) || (c < b) is %d \n", result);
    result = (a != b) || (c < b);
    printf("(a != b) || (c < b) is %d \n", result);
    result = !(a != b);
    printf("!(a != b) is %d \n", result);
    result = !(a == b);
    printf("!(a == b) is %d \n", result);
    return 0;
}

输出

(a == b) && (c > b) is 1
(a == b) && (c < b) is 0
(a == b) || (c < b) is 1
(a != b) || (c < b) is 0
!(a != b) is 1
!(a == b) is 0

逻辑运算符程序解析

• (a == b) && (c > 5) 两操作数均为 1，结果 1。
• (a == b) && (c < b) 第二操作数为 0，结果 0。
• (a == b) || (c < b) 第一操作数为 1，结果 1。
• (a != b) || (c < b) 两操作数均为 0，结果 0。
• !(a != b) 操作数为 0，取反为 1。
• !(a == b) 操作数为 1，取反为 0。

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C 位运算符

计算时数学运算转为位级操作，更快更省电。位运算符用于位级操作。

运算符	含义
&	按位与
|	按位或
^	按位异或
~	按位取反
<<	左移
>>	右移

详见 C 语言位运算符详解。

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其他运算符

逗号运算符

关联相关表达式：

int a, c = 5, d;

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sizeof 运算符

一元运算符，返回数据（常量、变量、数组、结构体等）大小。

示例 6：sizeof 运算符

#include <stdio.h>
int main() {
    int a; float b; double c; char d;
    printf("Size of int=%lu bytes\n", sizeof(a));
    printf("Size of float=%lu bytes\n", sizeof(b));
    printf("Size of double=%lu bytes\n", sizeof(c));
    printf("Size of char=%lu byte\n", sizeof(d));
    return 0;
}

输出

Size of int = 4 bytes
Size of float = 4 bytes
Size of double = 8 bytes
Size of char = 1 byte

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三元运算符 ?:、取地址运算符 &、解引用运算符 *、成员选择运算符 -> 将在后续教程讨论。