Introduction notes to C + + Basics (III) operator Basics

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The content is based on the dark horse programmer c + + course handout. I added a small part and put it here as a reference for my review in the future. (this introductory course is highly recommended. It's available on website B)

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3 operator

Function: used to perform code operations

In this chapter, we mainly explain the following types of operators:

3.1 arithmetic operators

Function: used to process four operations

Arithmetic operators include the following symbols:

Example 1:

#include<iostream>
using namespace std;

//add , subtract , multiply and divide
int main() 
{
	int a1 = 10;
	int b1 = 3;

	cout << a1 + b1 << endl;
	cout << a1 - b1 << endl;
	cout << a1 * b1 << endl;
	cout << a1 / b1 << endl;  //The output is 3 because the result of dividing two integers is still an integer

	int a2 = 10;
	int b2 = 20;
	cout << a2 / b2 << endl; //The output is 0, also because the result of dividing two integers is still an integer

	int a3 = 10;
	int b3 = 0;
	//cout << a3 / b3 << endl; // An error is reported. The divisor cannot be 0


	//Two decimals can be divided
	double d1 = 0.5;
	double d2 = 0.25;
	cout << d1 / d2 << endl; //The output is 2 because it is exactly divisible. Non divisible decimals will be decimals

	system("pause");

	return 0;
}

Summary:

• In a division operation, the divisor cannot be 0
• The result of dividing two integers is still an integer. Remove the decimal part

Example 2:

#include<iostream>
using namespace std;

//Take the mold, that is, take the remainder
int main() {

	int a1 = 10;
	int b1 = 3;

	cout << 10 % 3 << endl;  //The result is 1

	int a2 = 10;
	int b2 = 20;

	cout << a2 % b2 << endl; //The result is 10

	int a3 = 10;
	int b3 = 0;

	//cout << a3 % b3 << endl; // An error is reported because the divisor cannot be 0 during modulo operation

	//Two decimals cannot be modulo
	double d1 = 3.14;
	double d2 = 1.1;

	//cout << d1 % d2 << endl; // An error is reported because modulo operation can only be performed on integers

	system("pause");

	return 0;
}

Summary:

• Only integer variables can perform modulo operations, which is essentially the remainder
• Two decimals cannot be modulo

Example 3:

#include<iostream>
using namespace std;

//Increasing
int main() 
{
	//1. Pre increment
	int b = 10;
	++b; //Add 1 to the variable
	cout << b << endl; 
    //The result is: 11
    
    //2. Post increment
	int a = 10;
	a++; //Equivalent to a = a + 1
	cout << a << endl; 
    //The result is: 11

	//3. Difference between pre and post
	//Pre increment first + + the variable, and then calculate the expression
	int a2 = 10;
	int b2 = ++a2 * 10;
	cout << b2 << endl; 
    //The result is 110

	//Post increment calculates the expression first, and then calculates the variable++
	int a3 = 10;
	int b3 = a3++ * 10;
	cout << b3 << endl; 
    //The result is: 100

	system("pause");

	return 0;
}

Summary:

• Pre increment first + + the variable, and then calculate the expression
• In contrast to post increment, the expression is calculated first and then++

3.2 assignment operator

Function: used to assign the value of an expression to a variable

The assignment operator includes the following symbols:

Example:

#include<iostream>
using namespace std;

int main() 
{
	//Assignment Operators 

	// Equals=
	int a = 10;
	a = 100; //Reassign a
	cout << "a = " << a << endl;
    //The result is 100

	// Plus equals+=
	a = 10; //Reassign a
	a += 2; // Equivalent to a = a + 2;
	cout << "a = " << a << endl;
    //The result is 12

	// Minus equals-=
	a = 10; //Reassign a
	a -= 2; // Equivalent to a = a - 2
	cout << "a = " << a << endl;
    //The result is 8

	// Multiply equal*=
	a = 10; //Reassign a
	a *= 2; // Equivalent to a = a * 2
	cout << "a = " << a << endl;
    //The result is 20

	// Division equals/=
	a = 10; //Reassign a
	a /= 2;  // Equivalent to a = a / 2;
	cout << "a = " << a << endl;
    //The result is 5

	// Modulus equal to%=
	a = 10; //Reassign a
	a %= 2;  // A = 2;
	cout << "a = " << a << endl;
    //The result is 0

	system("pause");

	return 0;
}

3.3 comparison operator

Function: used to compare expressions and return a true value or false value

The comparison operator has the following symbols:

Example:

#include<iostream>
using namespace std;

int main() 
{
	int a = 10;
	int b = 20;

	cout << (a == b) << endl; //The expression should be enclosed in parentheses, otherwise the output symbol will be regarded as two less than signs
    // 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
	
	system("pause");

	return 0;
}

Note: in the comparison operation of C and C + + languages, "true" is represented by the number "1", and "false" is represented by the number "0".

3.4 logical operators

Function: used to return true or false values according to the value of the expression

Logical operators have the following symbols:

Example 1: logical non

//Logical operator --- not
int main() {

	int a = 10;

	cout << !a << endl; // 0

	cout << !!a << endl; // 1

	system("pause");

	return 0;
}

Summary: reverse operation, true to false, false to true

Example 2: logic and

//Logical operators --- and
int main() {

	int a = 10;
	int b = 10;

	cout << (a && b) << endl; //Be careful to have parentheses
    // 1

	a = 10;
	b = 0;

	cout << (a && b) << endl;// 0 

	a = 0;
	b = 0;

	cout << (a && b) << endl;// 0

	system("pause");

	return 0;
}

Summary: logic and operator summary: 8-word truth = = the same truth is true, and the rest are false==

Example 3: logical or

//Logical operator --- or
int main() {

	int a = 10;
	int b = 10;

	cout << (a || b) << endl; //Be careful to have parentheses
    // 1

	a = 10;
	b = 0;

	cout << (a || b) << endl;// 1 

	a = 0;
	b = 0;

	cout << (a || b) << endl;// 0

	system("pause");

	return 0;
}

Logical or operator summary: 8-character true words are false if they are the same as false, and the rest are true