C++| Ingenious work from 0 to 1 introductory programming [video + courseware + notes + source code]
table of Contents
3 operator
Role: used to execute the operation of the code.
In this chapter, we mainly explain the following types of operators:
Operator type effect Arithmetic Operator Used to handle the four arithmetic operations Assignment operator Used to assign the value of an expression to a variable Comparison operator Used to compare expressions and return a true or false value Logical Operators Used to return true or false based on the value of the expression
3.1 Arithmetic operators
Role : Used to process four arithmetic operations.
Arithmetic operators include the following symbols:
Operator the term Example result + Positive sign +3 3 - negative -3 -3 + plus 10 + 5 15 - Less 10 - 5 5 * Multiply 10 * 5 50 / except 10 / 5 2 % Modulus (take remainder) 10 % 3 1 ++ Pre-increment a=2; b=++a; a=3; b=3; ++ Post-increment a=2; b=a++; a=3; b=2; -- Pre-decrement a=2; b=--a; a=1; b=1; -- Post-decreasing a=2; b=a--; a=1; b=2;
Example 1
#include <iostream>
using namespace std;
int main()
{
int a1 = 10;
int b1 = 3;
cout << a1 + b1 << endl; // 13
cout << a1 - b1 << endl; // 7
cout << a1 * b1 << endl; // 30
cout << a1 / b1 << endl; // 3 两个整数相除,结果依然是整数,将小数部分去除
int a2 = 10;
int b2 = 20;
cout << a2 / b2 << endl; // 0
int a3 = 10;
int b3 = 0;
//错误！两个数相除，除数不可以为0！
//cout << a3 / b3 << endl; //报错，除数不可以为0。
//两个小数可以相除
double d1 = 0.5;
double d2 = 0.25;
cout << d1 / d2 << endl; // 2 运算结果可以是整数
d1 = 0.5;
d2 = 0.22;
cout << d1 / d2 << endl; // 2.27273 运算结果可以是小数
system("pause");
return 0;
}Summary: In the division operation, the divisor cannot be 0.
Example 2
#include <iostream>
using namespace std;
int main()
{
int a1 = 10;
int b1 = 3;
cout << a1 % b1 << endl; // 1
int a2 = 10;
int b2 = 20;
cout << a2 % b2 << endl; // 10
int a3 = 10;
int b3 = 0;
//两个数相除，除数不可以为0，所以做不了取模运算
// cout << a3 % b3 << endl; // 报错。取模运算时，除数不能为0！
//两个小数是不可以做取模运算的
double d1 = 3.14;
double d2 = 1.1;
// cout << d1 % d2 << endl; // 报错
system("pause");
return 0;
}Summary: Only integer variables can perform modulo operation.
Example 3
#include <iostream>
using namespace std;
int main() //递增
{
//1、前置递增
int a = 10;
++a; //让变量+1
cout << "a = " << a << endl; // 11
//2、后置递增
int b = 10;
b++; //让变量+1,等价于b = b + 1
cout << b << endl; // 11
//3、前值和后置的区别
//前置递增：先对变量进行++，再计算表达式
int a2 = 10;
int b2 = ++a2 * 10;
cout << "a2 = " << a2 << endl; // 11
cout << "b2 = " << b2 << endl; // 11 * 10 -> 110
//后置递增：先计算表达式，后对变量进行++
int a3 = 10;
int b3 = a3++ * 10;
cout << "a3 = " << a3 << endl; // 11
cout << "b3 = " << b3 << endl; // 100
system("pause");
return 0;
}
Summary: Pre-increment ++ is performed on the variable first, and then the expression is calculated, and post-increment is the opposite.
3.2 Assignment operator
Role: Used to assign the value of an expression to a variable .
The assignment operator includes the following symbols:
Operator the term Example result = Assignment a=2; b=3; a=2; b=3; += Plus equals a=0; a+=2; a=2; -= Minus is equal to a=5; a-=3; a=2; *= Multiply equals a=2; a*=2; a=4; /= Divide equal to a=4; a/=2; a=2; %= Modulo equal a=3; a%2; a=1;
Example
#include <iostream>
using namespace std;
int main() // 赋值运算符
{
// =
int a = 10;
a = 100;
cout << "a = " << a << endl; // a = 100
// +=
a = 10;
a += 2; // a = a + 2;
cout << "a = " << a << endl; // a = 12
// -=
a = 10;
a -= 2; // a = a - 2
cout << "a = " << a << endl; // a = 8
// *=
a = 10;
a *= 2; // a = a * 2
cout << "a = " << a << endl; // a = 20
// /=
a = 10;
a /= 2; // a = a / 2;
cout << "a = " << a << endl; // a = 5
// %=
a = 10;
a %= 2; // a = a % 2;
cout << "a = " << a << endl; // a = 0
return 0;
}3.3 Comparison operators
Function: Used to compare expressions and return a true or false value.
Comparison operators have the following symbols:
Operator the term Example result == equal to 4 == 3 0 != not equal to 4 != 3 1 < Less than 4 < 3 0 > more than the 4 > 3 1 <= Less than or equal to 4 <= 3 0 >= greater or equal to 4 >= 1 1
Example
#include <iostream>
using namespace std;
int main() // 比较运算符
{
int a = 10;
int b = 20;
// ==
cout << (a == b) << endl; // 0
// !=
cout << (a != b) << endl; // 1
// >
cout << (a > b) << endl; // 0
// <
cout << (a < b) << endl; // 1
// >=
cout << (a >= b) << endl; // 0
// <=
cout << (a <= b) << endl; // 1
return 0;
}Note: In C and C++ language comparison operations, "true" is represented by the number "1", and "false" is represented by the number "0" .
3.4 Logical operators
Function: It is used to return true or false value according to the value of the expression.
Logical operators have the following symbols:
Operator the term Example result ! non- !a If a is false, then !a is true; if a is true, then !a is false. && versus a && b If both a and b are true, the result is true, otherwise it is false. || or a || b If one of a and b is true, the result is true, and when both are false, the result is false.
Example 1: Logical NOT
#include <iostream>
using namespace std;
int main()
{
//逻辑运算符 --- 逻辑非
int a = 10;
//在C++中，除了0都为真
cout << !a << endl; // 0
cout << !!a << endl; // 1
system("pause");
return 0;
}Summary: True becomes false, and false becomes true.
Example 2: Logical AND
#include <iostream>
using namespace std;
int main()
{
//逻辑运算符 --- 逻辑与 &&
int a = 10;
int b = 10;
cout << (a && b) << endl; // 1
a = 10;
b = 0;
cout << (a && b) << endl; // 0
a = 0;
b = 0;
cout << (a && b) << endl; // 0
//同真为真，其余为假！
system("pause");
return 0;
}Summary: logical AND operator summary: the same truth is true, the rest are false .
Example 3: Logical OR
#include <iostream>
using namespace std;
int main()
{
//逻辑运算符 --- 逻辑或
int a = 10;
int b = 10;
cout << (a || b) << endl; // 1
a = 10;
b = 0;
cout << (a || b) << endl; // 1
a = 0;
b = 0;
cout << (a || b) << endl; // 0
//逻辑或运算符总结：同假为假，其余为真！
system("pause");
return 0;
}Logical OR operator summary: the same false is false, the rest are true .