Operators and Expressions

Operator: it refers to the symbols involved in the operation. The variables operated with the operator are called operands

Expression: it is a formula composed of variables or direct quantities and operators. The expression will have a calculation result, which is called the value of the expression

Concepts of operators and expressions

In applications, data is often operated, so le C language provides many types of operators, that is, symbols specially used to tell programs to perform specific operations or logical operations
There are seven common categories:

Operator type	effect
Arithmetic operator	Used to process four operations
Relational operator	Used to compare expressions and return a true or false value
Logical operator	Used to return true or false values based on the value of an expression
Assignment Operators	Used to assign the value of an expression to a variable
Conditional operator	Used for processing condition judgment
Bitwise Operators	Bit operation for processing data
sizeof operator	Used to find byte length

Arithmetic operators and arithmetic expressions

The arithmetic operator in C language is the symbol used to deal with four operations
Let's go straight to the figure above 🚗🚓🚕🛺🚙🛻

operator	name	Real column	Operation result
+	Plus sign	+3	3
-	minus sign	a=4;-a;	-4
+	plus	1+1	2
-	minus sign	2-1	1
*	ride	9*9	81
/	except	6/3	2
%	Mod	6%5	1
++	Self increasing (front)	a=2;b=++a;	b=3;a=3;
++	Self subtraction (front)	a=2;b=- -a;	b=1;a=1;
–	Self increasing (rear)	a=2;b=a++;	b=2;a=3;
–	Self subtraction (rear)	a=2;b=a- -	b=2;a=1;

With regard to self increase and self decrease, we must pay attention to:
(+ sign first) + + a indicates that a is participating in other operations after self increment
(- sign first) - A indicates that a is participating in other operations after subtraction
(+ sign after) a + + indicates that the value of a increases by 1 after participating in the operation
(- sign after) -- ab indicates that the value of a after participating in the operation is minus 1

Arithmetic expression
Expressions connected by arithmetic operators are called arithmetic expressions.
Upper Code:

#include<stdio.h> 
int main()
{
	int a,b,c,x,y,z;
	a=1;
	b=2;
	c=3;
	printf("%d\n",a+b);
	printf("Self increment (front):%d\n" ,++a);  //A increases automatically, 1 + 1 = 2, and is stored in A. at this time, the value in a has changed to 2 (no longer 1), and the output result in the operation is 2. 
	 printf("Self increasing (after):%d\n",a++);   //A operates first, because the value stored in a is 2, so a=2. At this time, the operation is assigned to a=2. The output result of the operation is 2. Then it increases automatically to get a=3. Later, the result is obtained by self increment and stored in a, but it is not used
	 printf("here a Value of:%d\n",a); //In this step, we use, which is equal to 3, so the output of the operation is a=3 
	printf("Self subtraction (after):%d\n",b--);//First b operation, the value assigned to a above is 2, so b=2, the output value is 2, and then self subtraction, 2-1 = 1. At this time, the value stored in b is 1 
	printf("Self subtraction (front):%d\n",--b);//Self subtraction first, because the value stored in b in the previous step is 1, b=1, so 1-1 = 0. Then, during operation, the value of output b is 1
	printf("Self subtraction (front):%d\n",--c);
	printf("The value of remainder is:%d\n",7%5);
}
//The operation result is:
3
 Self increasing (front): 2
 Self increasing (rear): 2
 here a Value of: 3
 Self subtraction (after): 2
 Self subtraction (front): 0
 Self subtraction (front): 2
 The value of remainder is: 2

Relational operators and expressions

The operator that judges the relationship between two data is called relational operator, also known as comparison operator

operator	operation	The Works of Liezi	result
==	Equal to	1==2	0 (false)
!=	Not equal to	1!=2	1 (true)
<	less than	1<2	1 (true)
>	greater than	1>2	0 (false)
<=	Less than or equal to	1<=2	1 (true)
>=	Greater than or equal to	1>=2	0 (false)

Relational operators are binocular operators. They need two variables in operation, such as a > B
Relational expression
Expressions connected by relational operators are called relational expressions

#include<stdio.h> 
main()
{
	int x,y,z;
	//Variable description (Declaration)
    //The variable declaration in the function must be placed at the top of the function body
 
	int max(int a,int b);
	//Function declaration (description)
 
	printf("Enter two integers,Judge size:");
	//Output string
 
	scanf("%d\n %d",&x,&y);
	//Enter values for x and y,
	//scanf() is a built-in input function
 
	z=max(x,y);
	//First call the max() function,
	//Then assign the value returned by the max() function to z
 
	printf("The maximum number is: %d \n",z);
	//Output string
	//printf() is a built-in output function
}
//Main function (main)
 
int max(int a,int b)
{
	if (a>b) return a;else return b;
}
//Custom max function

Logical operators and logical expressions

Logical operators are used to judge whether a compound condition is true or false, and the result is still (true) or (false)

operator	name	The Works of Liezi	result
&&	And	a&&b	If both a and b are true, the result is true, otherwise it is false
!	wrong	!a	If a is false,! A is true, otherwise it is false
II	or	aIIb	True if one or more of a and b are true, otherwise false

Logical expression
Expressions connected by logical operators are called logical expressions
The code was seen by the blogger Xinyuan's wife

#include<stdio.h> 
int main()
{
int age=0; // Age 18-30
int height=0; // Height 165-175 cm
int sc=0; // Figure, 1-hot; 2-ordinary; 3-airport.
int yz=0; // Appearance, 1-beautiful; 2-average; 3-crooked melon split jujube (Cuihua).
printf("Please enter age, height and figure(1-Hot; 2-Ordinary; 3-airport)(Separated by spaces): ");
scanf("%d %d %d",&age,&height,&sc);
printf("Please enter a color value(1-Beautiful; 2-General; 3-Crooked melon split jujube (Cuihua)): ");
scanf("%d",&yz);
if ( ( (age >= 18) && (age <= 30) ) && // Aged between 25 and 30
( (height >= 165) && (height <= 175) ) && // Height between 165-175
 Both must be true
( (sc == 1) ) && // Figure, 1-hot
( (yz == 1) || (yz == 2) ) ) // Appearance, 1-beautiful or 2-average
//One of the two is true
{
printf("Super girl draft qualified, sent to the harem.\n");
}
else
{
printf("If you fail in the super girl draft, you will be given five Liang silver and sent home.\n");
}
}

Assignment operators and assignment expressions

The assignment operator is used to assign the value of a constant, variable or expression to a variable

operator	name	The Works of Liezi	result
=	assignment	a=3;b=2;	a=3;b=2;
+=	Plus equals	a=3;b=2;a+=b;	a=5;b=2
-=	Minus equals	a=3;b=2;a-=b	a=1;b=2
*=	Multiply equal	a=3;b=2;a*=b;	a=6;b=2
/=	Division equals	a=3;b=2;a/=b	a=1;b=2
%=	Modulo equal (remainder)	a=3;b=2;a%=b;	a=1;b=2

a+=b ----------- a=a+b
a-=b ------------a=a-b

#include<stdio.h>
int main()
{
	int a=5;
	int b=(a=5);
	printf("%d\n",b);
	int x,y,z;
	x=y=z=6;
	printf("Buddy:%d%d%d\n",x,y,z);
	int d=1;
	d+=1313;//d=d+1313
	printf("%d",d);
 } 
//Operation results:
5
 Old fellow: 666
1314

Conditional operators and conditional expressions

When writing programs, we often encounter conditional judgment
For example, if a > b is judged, an operation will be executed when a > b is true, and another operation will be executed when a > b is not true

Expression 1? Expression 2 : Expression 3

#include<stdio.h>
int main()
{
    int a = 10;
    int b = 20;
    int max = 0;
    max = (a > b ? a : b);//The effect and meaning of the following sentences
    /*if (a > b)
       max = a;
    else
       max = b;*/
    return 0;
}
/*Conditional Operator 
exp1?exp2:exp3
 If exp1 is true, it returns exp2; if false, it returns exp3*/

Bitwise Operators

Bit operator bit is the smallest unit of information in the computer, generally represented by 0 and 1. Bit operator is to operate its operands bit by bit according to its binary form.

sizeof operator

sizeof operator is provided in C language to obtain the number of bytes of a data or data type in memory

format

sizeof(Type specifier)
sizeof expression

#include<stdio.h>
typedef struct Worke
{
char name[10];
int age;
long ID;
float height;
double weight;
}worker_t;
int main()
{
printf("char    :%lu\n", sizeof( char));
printf("int     :%lu\n", sizeof(int));
printf("long    :%lu\n", sizeof(long));
printf("float   :%lu\n", sizeof(float));
printf("double  :%lu\n", sizeof(double));
printf("worker_t:%lu\n", sizeof(worker_t));
printf("1+2     :%lu\n", sizeof(1+ 2));
printf("1+2.5   :%lu\n", sizeof(1+2.5));
printf("\n");
return 0;
}



char    :1
int     :4
long    :4
float   :4
double  :8
worker_t:32
1+2     :4
1+2.5   :8

Operation priority

Operators in C language include monocular operator, binocular operator and ternary operator, and their priorities are as follows:

1. Priority 1: various parentheses, such as (), [] and member operators;
2. Priority 2: all monocular operators, such as + +, –,!, ~, etc;
3. Priority 3 (arithmetic operator): multiplication operator *, division operator /, remainder operator%
4. Priority 4 (arithmetic operator): addition operator +, subtraction operator -;
5. Priority 5 (shift operator): shift operators <, > >;
6. Priority 6 (conditional operator): greater than operator >, greater than or equal to operator > =, less than operator <, less than or equal to operator < =;
7. Priority 7 (conditional operator): equal operator = =, not equal operator! =;
8. Priority 8 (bitwise operator): bitwise and operator &;
9. Priority 9 (bitwise operator): bitwise XOR operator ^;
10. Priority 10 (bitwise operator): bitwise OR operator |;
11. Priority 11 (logic and operator): logic and operator & &;
12. 12th priority logic and operator: logic or operator |;
13. Priority 13: three item condition operator?:;
14. Priority 14: various assignment operators, such as =, + =, - =, * =, / =;
15. Priority 15: comma operation.

Arithmetic operators > shift operators > conditional operators > bitwise operators > logical operators > assignment

//Code in the blog Fanshi coffee to see
//Example of operator priority (not involving complex):
#include <stdio.h>
main() {
int a = 20;
int b = 10;
int c = 15;
int d = 5;
int 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; // (30 * 15 ) / 5
printf("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;}
//Operation results:
Value of (a + b) * c / d is : 90
Value of ((a + b) * c) / d is : 90
Value of (a + b) * (c / d) is : 90
Value of a + (b * c) / d is : 50

From now on, stick to it and make progress a little bit a day. In the near future, you will thank you for your efforts!

If something goes wrong again, please correct it.

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