Operators in C language

C Language operators

The precedence table of operators and ASCII surface
One 、 Arithmetic operator

• Add (+） reduce （—） ride （*） except （/）
• model （ more than ） Operator （%）： Floating point is not allowed , The remainder depends on the divisor

#include <stdio.h>
int main() {
    
    int i, b, a, c;
    i= 4, b=3;
    a= i+b;
    c= i*a;
    float p, k;
    p= i/b;
    k= i%a;
    printf("a=%d,c=%d,p=%f,k=%f\n",a,c,p,k);
    return 0;
}

[[email protected] c]# ./o
a=7,c=28,p=1.000000,k=4.000000

• Self increasing （++i,–i;i++,i–）

#include <stdio.h>
int main() {
    
    int i;
    i= 4;
    printf("%d\n",++i);
    return 0;
}

[[email protected]shuyi c]# ./o
5

#include <stdio.h>
int main() {
    
    int i;
    i= 4;
    printf("%d\n",i--);
    //printf("%d\n",i);  The output is 
    return 0;
}

[[email protected] c]# ./o
4

Two 、 Relational operator

• Greater than (>） Less than (<） be equal to (==）

#include <stdio.h>
int main() {
    
    int a, b, max;
    printf ("please enter a and b\n");
    scanf ("%d %d",&a, &b);
    if (a>b) max=a;
    if (a<b) max=b;
    if (a==b) max=a;
    printf ("max=%d\n",max);
    return 0;
}
[[email protected] c]# ./o
please enter a and b
55 66
max=66
[[email protected] c]# ./o
please enter a and b
44 44
max=44

• Less than or equal to (<=） Greater than or equal to (>=） It's not equal to (!=） assignment (-=、+=、*=);

#include<stdio.h>
int main(){
    
    int a = 10;
    a +=a *=a -=20;
    printf("%d\n",a);
}

[[email protected] c]# ./ass
200



#include <stdio.h>
int main() {
    
    int a, b, max;
    printf ("please enter a and b\n");
    scanf ("%d %d",&a, &b);
    if (a>=b) max=a;
    if (a<=b) max=b;
    printf ("max=%d\n",max);
    return 0;
}
[[email protected] c]# ./o
please enter a and b
55 66
max=66
[[email protected] c]# ./o
please enter a and b
77 77
max=77

#include <stdio.h>
int main() {
    
    int a, b, max;
    printf ("please enter a and b\n");
    scanf ("%d %d",&a, &b);
    if (a!=b);
    if (a>b) max=a;
    if (a<b) max=b;
    printf ("max=%d\n",max);
    return 0;
}
[[email protected] c]# ./o
please enter a and b
44 44
max=0
[[email protected] c]# ./o
please enter a and b
44 55
max=55

3、 ... and 、 Logical operators （ also 、 perhaps 、 Unless ）
PS： Priority from top to bottom

• Logic is not (! NOT）

#include <stdio.h>
int main() {
    
    int num = 0;
    printf ("Please enter num value: ");
    scanf("%d", &num);
    if (num != 69) {
    
       printf ("num %d is not equal to 69.\n", num);
    }
    return 0;
}
~
[[email protected] c]# ./o
Please enter num value: 69
[[email protected] c]# ./o
Please enter num value: 1
num 1 is not equal to 69.

• Logic and (&& AND）

#include <stdio.h>
int main() {
    
    int a, b, x, y;
    printf ("please enter a and b,x and y\n");
    scanf ("a=%d,b=%d,x=%d,y=%d",&a, &b, &x, &y);
    if (a==b && x==y){
    
    printf ("a=b,x=y\n");
    }
    else
    printf ("sorry,I donot konw.\n");
    return 0;
}
[[email protected] c]# ./o
please enter a and b,x and y
a=1,b=2,x=1,y=1
sorry,I donot konw.
[[email protected] c]# ./o
please enter a and b,x and y
a=1,b=1,x=2,y=2
a=b,x=y

• Logic or (|| OR）

Four 、 An operator

• Move right (>>） Move left (<<）
• Bitwise AND (&）
• Press bit or (|）
• Bitwise XOR (^）
• Take the opposite (~)

5、 ... and 、 Assignment operator

• Equal sign (=）
• Extended assignment operators
  += Add the assignment (a += 3 Equivalent to a = a + 3）
  -= Assignment reduction
  *= Take the assignment
  /= In addition to the assignment
  %= Complementary valuation
  &= Bitwise and assignment
  | = By bit or by assignment
  ^= Assign values by bitwise exclusive or
  <<= Left shift assignment （>>= Right shift assignment ）
  <> When the right operand is another assignment expression , Form multiple assignment expressions

6、 ... and 、 Conditional operator
PS： Conditional operators take precedence over assignment 、 The comma operator , Lower than other operators .

• Relationship expression ？ expression 1 ： expression 2
  Ternary operator ： Conditions ? result 1 : result 2
  Example ：
  Judge a Less than or greater than b, Output Max max

#include <stdio.h>
int main(){
    
  int a, b, max;
  scanf("a=%d,b=%d",&a,&b);
  max=a>b?a:b;
  printf("max=%d\n",max);
  return 0;
}
[[email protected] c]# gcc -o swap swap.c
[[email protected] c]# ./swap
a=2,b=3
max=3

7、 ... and 、 The comma operator （,）

#include<stdio.h>
int main(){
    
    int i = 1;
    int a = (i+100,i++,i);
    printf("%d\n",a);
    return 0;
}
[[email protected] c]# ./comma
2

#include<stdio.h>
int main(){
    
    int i = 1;
    int a = (i=i+100,i++,i);
    printf("%d\n",a);
    return 0;
}
[[email protected] c]# ./comma
102

8、 ... and 、 Pointer operator

• Pointer to the variable (*）
  Definition ： Base type * Pointer variable name ;
  Example 1： Access integer variables through pointer variables

#include <stdio.h>
int main() {
    
    int a, b; # Define two int Variable 
    int * pointer_1, * pointer_2; # Define two pointer variables , Point to int Variable 
    a = 100; b = 10;
    pointer_1 = &a; # Put variables a To the pointer pointer_1
    pointer_2 = &b;
    printf ("a = %d, b = %d \n", a, b);
    printf (" * pointer_1 = %d, * pointer_2 = %d \n", * pointer_1, * pointer_2); # The value of the integer variable pointed to by the output pointer variable 
    return 0;
}

~
[[email protected] c]# gcc -o pointer1 pointer1.c
[[email protected] c]# ./pointer1
a = 100, b = 10
 * pointer_1 = 100, * pointer_2 = 10
[[email protected] c]# vi pointer1.c

Example 2： Than the size

#include <stdio.h>
int main () {
    
    int * p1, * p2, * p, a, b;
    scanf ("%d, %d", &a, &b);
    p1 = &a; p2 = &b;
    if (a < b) {
    
       p = p1; p1 = p2; p2 = p;
       }
       printf ("a = %d, b = %d\n", a, b);
       printf ("max = %d, min = %d\n", * p1, * p2);
    return 0;
}
r
[[email protected] c]# ./pointer2
4,6
a = 4, b = 6
max = 6, min = 4

Example 3： The arithmetic

#include <stdio.h>
int main () {
    
    int maxsum = 123;
    double temp = 888.8889922111111;
    temp  += (float)maxsum;
    printf ("%7.3f, %d\n", (float)temp, (int)temp);
    return 0;
}
[[email protected] c]# gcc -o compulsion compulsion.c
[[email protected] c]# ./compulsion
1011.889, 1011

Nine 、 Find byte operator （sizeof）

• When sizeof( And data types （ Such as int,float,char … etc. ） When used together , Returns the amount of memory allocated to the data type .

#include<stdio.h>
int main()
{
    
    printf("%d\n",sizeof(char));
    printf("%d\n",sizeof(int));
    printf("%d\n",sizeof(float));
    printf("%d\n", sizeof(double));
    return 0;
}

• When sizeof When used with expressions , Returns the size of the expression .

#include<stdio.h>
int main() {
    
    int a = 1, b = 3;
    printf ("%d\n", sizeof ( a + b ));
    return 0;
    }
    
[[email protected] c]# gcc -o sizeof1 sizeof1.c
[[email protected] c]# ./sizeof1
4

Ten 、 Cast operators

example 1： Decimal to integer

#include <stdio.h>
int main () {
    
    float f = 8.88;
    int i;
    i = (int) f;
    printf ("f = %f, i = %d \n", f, i);
    return 0;
}

[[email protected] c]# gcc -o compulsion compulsion.c
[[email protected] c]# ./compulsion
f = 8.880000, i = 8

example 2： Integer to decimal

#include <stdio.h>
int main () {
    
    int maxsum = 123;
    printf ("%lf\n", (double) maxsum);
    return 0;
}

[[email protected] c]# gcc -o compulsion compulsion.c
[[email protected] c]# ./compulsion
123.000000

11、 ... and 、 member operator

• member operator (.）
• Indirect member operator (–>）

Twelve 、 Subscript operator （[ ]）

PS： Precedence and associativity of operators