operator

Role: Operations used to execute code

In this chapter, we will focus on the following types of operators:

Operator type	Effect
Arithmetic Operators	For four operations
Assignment Operators	Used to assign the value of an expression to a variable
Comparison operator	Used for comparison of expressions and returns a true or false value
Logical operators	Used to return true or false values based on the value of an expression

1. Arithmetic Operators

Role: For four operations

Arithmetic operators include the following symbols:

operator	term	Example	Result
+	Positive sign	+3	3
-	Minus sign	-3	-3
+	plus	10 + 5	15
-	reduce	10 - 5	5
*	ride	10 * 5	50
/	except	10 / 5	2
%	Modular (Remaining)	10 % 3	1
++	Pre-increment	a=2; b=++a;	a=3; b=3;
++	Postincrement	a=2; b=a++;	a=3; b=2;
–	Pre-Decreasing	a=2; b=–a;	a=1; b=1;
–	Posterior Decrease	a=2; b=a–;	a=1; b=2;

Example 1:

//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;  //Divide two integers and the result is still an integer

	int a2 = 10;
	int b2 = 20;
	cout << a2 / b2 << endl; 

	int a3 = 10;
	int b3 = 0;
	//Cout << A3 / B3 << endl; // Error, divisor cannot be 0


	//Two decimals can be divided
	double d1 = 0.5;
	double d2 = 0.25;
	cout << d1 / d2 << endl;

	system("pause");

	return 0;
}

Summary: In a division operation, the divisor cannot be zero

Example 2:

//Modeling
int main() {

	int a1 = 10;
	int b1 = 3;

	cout << 10 % 3 << endl;

	int a2 = 10;
	int b2 = 20;

	cout << a2 % b2 << endl;

	int a3 = 10;
	int b3 = 0;

	//Cout << A3% B3 << endl; // Divider cannot be 0 in modulo operation

	//Two decimal numbers are not modular
	double d1 = 3.14;
	double d2 = 1.1;

	//cout << d1 % d2 << endl;

	system("pause");

	return 0;
}

Summary: Only integer variables can be modulated

Example 3:

//Incremental
int main() {

	//Postincrement
	int a = 10;
	a++; //Equivalent to a = a + 1
	cout << a << endl; // 11

	//Pre-increment
	int b = 10;
	++b;
	cout << b << endl; // 11

	//Difference
	//Pre-increment adds ++ to the variable before calculating the expression
	int a2 = 10;
	int b2 = ++a2 * 10;
	cout << b2 << endl;

	//Post-increment first evaluates the expression, then ++ the variable
	int a3 = 10;
	int b3 = a3++ * 10;
	cout << b3 << endl;

	system("pause");

	return 0;
}

Summary: Pre-increment adds ++ to the variable before calculating the expression, and then adds up the opposite

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2. Assignment Operators

Role: Used to assign the value of an expression to a variable

Assignment operators include the following symbols:

operator	term	Example	Result
=	assignment	a=2; b=3;	a=2; b=3;
+=	Add equals	a=0; a+=2;	a=2;
-=	Subtract equals	a=5; a-=3;	a=2;
*=	Multiply equals	a=2; a*=2;	a=4;
/=	Divide equals	a=4; a/=2;	a=2;
%=	Modulo equals	a=3; a%2;	a=1;

Example:

int main() {

	//Assignment Operators

	// =
	int a = 10;
	a = 100;
	cout << "a = " << a << endl;

	// +=
	a = 10;
	a += 2; // a = a + 2;
	cout << "a = " << a << endl;

	// -=
	a = 10;
	a -= 2; // a = a - 2
	cout << "a = " << a << endl;

	// *=
	a = 10;
	a *= 2; // a = a * 2
	cout << "a = " << a << endl;

	// /=
	a = 10;
	a /= 2;  // a = a / 2;
	cout << "a = " << a << endl;

	// %=
	a = 10;
	a %= 2;  // a = a % 2;
	cout << "a = " << a << endl;

	system("pause");

	return 0;
}

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3. Comparison Operators

Role: Used to compare expressions and return a true or false value

The comparison operator has the following symbols:

operator	term	Example	Result
==	Equal to	4 == 3	0
!=	Not equal to	4 != 3	1
<	less than	4 < 3	0
>	greater than	4 > 3	1
<=	Less than or equal to	4 <= 3	0
>=	Greater than or equal to	4 >= 1	1

Example:

int main() {

	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
	
	system("pause");

	return 0;
}

Note: In the comparative operation between C and C++, True is represented by the number 1 and False is represented by the number 0.

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4. Logical Operators

Role: Used to return true or false values based on the value of an expression

Logical operators have the following symbols:

operator	term	Example	Result
!	wrong	!a	If a is false, then! a is true; If a is true, then! a is false.
&&	and	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 if both are false, the result is false.

Example 1: Logical NOT

//Logical Operator - Not
int main() {

	int a = 10;

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

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

	system("pause");

	return 0;
}

Summary: True to False, False to True

Example 2: Logical and

//Logical Operator--And
int main() {

	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

	system("pause");

	return 0;
}

Summary: Summary of Logic and Operators: True as True, False as Others

Example 3: Logical or

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

	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

	system("pause");

	return 0;
}

Summary of logic or operator: duplicate false, remaining true

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Reference resources: https://www.bilibili.com/video/BV1et411b73Z?p=15&t=271