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C语言运算符与流程控制详解

news 2025/9/30 18:49:14

运算符概述

运算符是告诉编译器执行特定数学或逻辑功能的符号。C语言包含丰富的内置运算符，主要分为以下几类：

算术运算符

假设变量A的值为10，变量B的值为20：

操作符	描述	例子
+	加两个操作数	A + B = 30
-	从第一个减去第二个操作数	A − B = -10
*	将两个操作数相乘	A * B = 200
/	将分子除以除分母	B / A = 2
%	模运算符和整数除法后的余数	B % A = 0
++	增量运算符将整数值增加一	A++ = 11
--	减量运算符将整数值减一	A-- = 9

#include <stdio.h>int main() {int a = 21;int b = 10;int c;c = a + b;printf("Line 1 - Value of c is %d\n", c);c = a - b;printf("Line 2 - Value of c is %d\n", c);c = a * b;printf("Line 3 - Value of c is %d\n", c);c = a / b;printf("Line 4 - Value of c is %d\n", c);c = a % b;printf("Line 5 - Value of c is %d\n", c);c = a++; printf("Line 6 - Value of c is %d\n", c);c = a--; printf("Line 7 - Value of c is %d\n", c);return 0;
}

关系运算符

假设变量A的值为10，变量B的值为20：

操作符	描述	例子
==	检查两个操作数的值是否相等	(A == B) 为 false
!=	检查两个操作数的值是否相等	(A != B) 为 true
>	检查左操作数的值是否大于右操作数	(A > B) 为 false
<	检查左操作数的值是否小于右操作数	(A < B) 为 true
>=	检查左操作数的值是否大于或等于右操作数	(A >= B) 为 false
<=	检查左操作数的值是否小于或等于右操作数	(A <= B) 为 true

#include <stdio.h>int main() {int a = 21;int b = 10;int c;if(a == b) {printf("Line 1 - a is equal to b\n");} else {printf("Line 1 - a is not equal to b\n");}if(a < b) {printf("Line 2 - a is less than b\n");} else {printf("Line 2 - a is not less than b\n");}if(a > b) {printf("Line 3 - a is greater than b\n");} else {printf("Line 3 - a is not greater than b\n");}/* 改变a和b的值 */a = 5;b = 20;if(a <= b) {printf("Line 4 - a is either less than or equal to b\n");}if(b >= a) {printf("Line 5 - b is either greater than or equal to a\n");}return 0;
}

逻辑运算符

假设变量A持有1，变量B持有0：

操作符	描述	例子
&&	逻辑与运算符。如果两个操作数都不为零，则条件为true	(A && B) 为 false
\|\|	逻辑或运算符。如果两个操作数中的任何一个不为零，则条件为true	(A \|\| B) 为 true
!	逻辑非运算符。用于反转其操作数的逻辑状态	!(A && B) 为 true

#include <stdio.h>int main() {int a = 5;int b = 20;int c;if(a && b) {printf("Line 1 - Condition is true\n");}if(a || b) {printf("Line 2 - Condition is true\n");}/* 改变a和b的值 */a = 0;b = 10;if(a && b) {printf("Line 3 - Condition is true\n");} else {printf("Line 3 - Condition is not true\n");}if(!(a && b)) {printf("Line 4 - Condition is true\n");}return 0;
}

按位运算符

按位运算符对位进行运算并执行逐位操作。假设A = 60，B = 13：

text

A = 0011 1100
B = 0000 1101
-----------------
A & B = 0000 1100
A | B = 0011 1101
A ^ B = 0011 0001
~A = 1100 0011

操作符	描述	例子
&	二进制AND运算符	(A & B) = 12，即0000 1100
\|	二进制OR运算符	(A \| B) = 61，即0011 1101
^	二进制XOR运算符	(A ^ B) = 49，即0011 0001
~	二进制补码运算符	(~A) = -61，即1100 0011
<<	二进制左移运算符	A << 2 = 240，即1111 0000
>>	二进制右移运算符	A >> 2 = 15，即0000 1111

#include <stdio.h>int main() {unsigned int a = 60; /* 60 = 0011 1100 */  unsigned int b = 13; /* 13 = 0000 1101 */int c = 0;           c = a & b;       /* 12 = 0000 1100 */ printf("Line 1 - Value of c is %d\n", c);c = a | b;       /* 61 = 0011 1101 */printf("Line 2 - Value of c is %d\n", c);c = a ^ b;       /* 49 = 0011 0001 */printf("Line 3 - Value of c is %d\n", c);c = ~a;          /* -61 = 1100 0011 */printf("Line 4 - Value of c is %d\n", c);c = a << 2;     /* 240 = 1111 0000 */printf("Line 5 - Value of c is %d\n", c);c = a >> 2;     /* 15 = 0000 1111 */printf("Line 6 - Value of c is %d\n", c);return 0;
}

赋值运算符

操作符	描述	例子
=	简单的赋值运算符	C = A + B
+=	加和赋值运算符	C += A 等价于 C = C + A
-=	减和赋值运算符	C -= A 等价于 C = C - A
*=	乘和赋值运算符	C = A 等价于 C = C A
/=	除和赋值运算符	C /= A 等价于 C = C / A
%=	模和赋值运算符	C %= A 等价于 C = C % A
<<=	左移和赋值运算符	C <<= 2 等价于 C = C << 2
>>=	右移和赋值运算符	C >>= 2 等价于 C = C >> 2
&=	按位与和赋值运算符	C &= 2 等价于 C = C & 2
^=	按位异或和赋值运算符	C ^= 2 等价于 C = C ^ 2
\|=	按位或和赋值运算符	C \|= 2 等价于 C = C \| 2

#include <stdio.h>int main() {int a = 21;int c;c = a;printf("Line 1 - = Operator Example, Value of c = %d\n", c);c += a;printf("Line 2 - += Operator Example, Value of c = %d\n", c);c -= a;printf("Line 3 - -= Operator Example, Value of c = %d\n", c);c *= a;printf("Line 4 - *= Operator Example, Value of c = %d\n", c);c /= a;printf("Line 5 - /= Operator Example, Value of c = %d\n", c);c = 200;c %= a;printf("Line 6 - %%= Operator Example, Value of c = %d\n", c);c <<= 2;printf("Line 7 - <<= Operator Example, Value of c = %d\n", c);c >>= 2;printf("Line 8 - >>= Operator Example, Value of c = %d\n", c);c &= 2;printf("Line 9 - &= Operator Example, Value of c = %d\n", c);c ^= 2;printf("Line 10 - ^= Operator Example, Value of c = %d\n", c);c |= 2;printf("Line 11 - |= Operator Example, Value of c = %d\n", c);return 0;
}

杂项运算符

操作符	描述	例子
sizeof()	返回变量的大小	sizeof(a)
&	返回变量的地址	&a
*	指向变量的指针	*a
?:	条件表达式	条件 ? 值1 : 值2

#include <stdio.h>int main() {int a = 4;short b;double c;int* ptr;/* sizeof运算符示例 */printf("Line 1 - Size of variable a = %lu\n", sizeof(a));printf("Line 2 - Size of variable b = %lu\n", sizeof(b));printf("Line 3 - Size of variable c = %lu\n", sizeof(c));/* & 和 * 运算符示例 */ptr = &a;        /* 'ptr' 现在包含 'a' 的地址 */printf("value of a is %d\n", a);printf("*ptr is %d.\n", *ptr);/* 三元运算符示例 */a = 10;b = (a == 1) ? 20 : 30;printf("Value of b is %d\n", b);b = (a == 10) ? 20 : 30;printf("Value of b is %d\n", b);return 0;
}

运算符优先级

运算符优先级确定表达式中术语的分组，并确定如何评估表达式。

类别	操作符	关联性
后缀	() [] -> . ++ --	左到右
一元	+ - ! ~ ++ -- (type) * & sizeof	右到左
乘性	* / %	左到右
加减	+ -	左到右
位移	<< >>	左到右
关系型	< <= > >=	左到右
相等	== !=	左到右
按位与	&	左到右
按位异或	^	左到右
按位或	\|	左到右
逻辑与	&&	左到右
逻辑或	\|\|	左到右
条件	?:	右到左
赋值	= += -= *= /= %= >>= <<= &= ^= \|=	右到左
逗号	,	左到右

#include <stdio.h>int main() {int a = 20;int b = 10;int c = 15;int d = 5;int e;e = (a + b) * c / d;      // (30 * 15) / 5printf("Value of (a + b) * c / d is : %d\n", e);e = ((a + b) * c) / d;    // (30 * 15) / 5printf("Value of ((a + b) * c) / d is : %d\n", e);e = (a + b) * (c / d);   // 30 * (15/5)printf("Value of (a + b) * (c / d) is : %d\n", e);e = a + (b * c) / d;     // 20 + (150/5)printf("Value of a + (b * c) / d is : %d\n", e);return 0;
}

流程控制 - 决策结构

C编程语言将任何非零和非null值假定为true，如果为零或null，则假定为false值。

if 语句

#include <stdio.h>int main() {int a = 10;if(a < 20) {printf("a is less than 20\n");}printf("value of a is : %d\n", a);return 0;
}

if...else 语句

#include <stdio.h>int main() {int a = 100;if(a < 20) {printf("a is less than 20\n");} else {printf("a is not less than 20\n");}printf("value of a is : %d\n", a);return 0;
}

嵌套 if 语句

#include <stdio.h>int main() {int a = 100;int b = 200;if(a == 100) {if(b == 200) {printf("Value of a is 100 and b is 200\n");}}printf("Exact value of a is : %d\n", a);printf("Exact value of b is : %d\n", b);return 0;
}

switch 语句

#include <stdio.h>int main() {char grade = 'B';switch(grade) {case 'A' :printf("Excellent!\n");break;case 'B' :case 'C' :printf("Well done\n");break;case 'D' :printf("You passed\n");break;case 'F' :printf("Better try again\n");break;default :printf("Invalid grade\n");}printf("Your grade is %c\n", grade);return 0;
}

嵌套 switch 语句

#include <stdio.h>int main() {int a = 100;int b = 200;switch(a) {case 100: printf("This is part of outer switch\n");switch(b) {case 200:printf("This is part of inner switch\n");}}printf("Exact value of a is : %d\n", a);printf("Exact value of b is : %d\n", b);return 0;
}