The control statements used to implement branch structure in c language mainly include if statement and switch statement.

Relational operator

operator	meaning
>	greater than
>=	Greater than or equal to
<	less than
<=	Less than or equal to
==	be equal to
!=	Not equal to

Relational expression:

The formula linking two expressions with relational operators is called relational expression. The general form of relational expression is:

Expression 1 relational operator expression

Function: compare the size of two expressions and return a logical value.

"=" is an assignment operator and "= =" is a relational operator

Since there is no data of logical type in c language, "1" represents "true" and "0" represents "false"

Logical operator

operator	!	&&	||
name	Logical non	Logic and	Logical or
Associativity	Right combination	Left combination	Left combination
priority	high	>	low

Logical operator

x	y	!x	x&&y	x||y
0	0	1	0	0
0	Not 0	1	0	1
Not 0	0	0	0	1
Not 0	Not 0	0	1	1

The order of precedence of various operators from high to low

operator	!	Arithmetic operator	Relational operator	&&And||	Assignment Operators
Associativity	Right combination	Left combination	Left combination	Left combination	Right combination
priority	high	>	>	>	low

Conditional operators and conditional expressions

Conditional operator: composed of "?" and ":" symbols, it is used for conditional evaluation. It is a ternary operator and requires three operands.

Conditional expression: the formula connecting three expressions is called conditional expression, and its general form is:

Expression 1? Expression 2: expression 3

If else statement

1. Double branch if statement   Its general form is:

if (expression)

  Statement 1;

else

  Statement 2;

2. Single branch if statement     Its general form is:

if (expression)

  sentence;

3. Multi branch if statement

if (expression 1)

  Statement 1;

else if (expression 2)

  Statement 2;

...

else if (expression n-1)

  Statement n-1;

else

  Statement n;

General form of switch statement:

switch (expression)

{     case constant expression 1: statement 1; break;

      case constant expression 2: Statement 2; break;

....

      case constant expression n: statement n; break;

    default: statement n+1; break;

}

 

#include<stdio.h>
#include<math.h>
int main()
{
 int a, b, c;
 float area;
 double s;
 printf("Please enter the three sides of the triangle:");
 scanf_s("%d,%d,%d", &a, &b, &c);
 s=(a + b + c) / 2.0;
 if (a + b <= c || b + c <= a || a + c <= b)
  printf("Does not form a triangle\n");
 else {
  area = sqrt(s * (s - a) * (s - b) * (s - c));
  printf("The area of the triangle is:%f\n", area);
 }
 return 0;
}

 

 

#include<stdio.h>
int main()
{
 int x; float y;
 printf("Please enter x Value of:");
 scanf_s("%d", &x);
 if (x != 0)
  y = 1.0 / x;
 else
  y = 0;
 printf("%d,%f", x, y);
 return 0;
}

 

 

#include<stdio.h>
int main()
{
 char c = 'm';
 int i = 10, j = 20, k = 30;
 float x = 13e+5, y = 10.85;
 printf("%d,%d,", 'a' + 5 < c, -i - 2 * j >= k + 1);
 printf("%d,%d,", 1 < j < 5, x - 5.25 <= x + y);
 printf("%d,%d\n", i + j + k == -2 * j, k == j == i + 5);
 return 0;
}

 

 

#include<stdio.h>
int main()
{
 int a = 3, b = 3, c = 2, d;
 printf("%d,", !a && !b && c);
 printf("%d,", !a || !b || c);
 printf("%d\n", a >= b && b > c);
 d = c-- || (b = 6) && a++;
 printf("a=%d,b=%d,c=%d,d=%d\n", a, b, c, d);
 return 0;
}

 

 

#include<stdio.h>
int main()
{
 int x, y;
 printf("Please enter two integers:");
 scanf_s("%d,%d", &x, &y);
 printf("The maximum of the two integers is:%d\n", x > y ? x : y);
 return 0;
}

 

 

#include<stdio.h>
int main()
{
 int a, b;
 printf("Please enter two integers:");
 scanf_s("%d%d", &a, &b);
 if (a > b)
  printf("The maximum number of two integers is:%d\n", a);
 else
  printf("The maximum of the two integers is:%d\n", b);
 return 0;
}

 

 

#include<stdio.h>
#include<math.h>
int main()
{
 double x, y;
 printf("input x Value of:");
 scanf_s("%lf", &x);
 if (x <= 1)
  y = exp(x);
 else
  y = pow(x, 2) - 1;
 printf("f(%f)=%.2f\n", x, y);
 return 0;
}

 

 

#include<stdio.h>
int main()
{
 float x;
 scanf_s("%f", &x);
 if (x < 0)
  x = -x;
 printf("%f", x);
 return 0;
}

 

 

#include<stdio.h>
int main()
{
 int x, y;
 printf("x=");
 scanf_s("%d", &x);
 if (x)
  y = 1;
 else
  y = -1;
 printf("y=%d", y);
 return 0;
}

 

 

#include<stdio.h >
int main()
{
 float a, b, c, t;
 scanf_s("%f,%f,%f", &a, &b, &c);
 if (a > b)
 {
  t = a; a = b, b = t;
 }
 if(a>c)
 {
  t = a, a = c, c = t;
 }
 if(b>c)
 {
  t = b, b = c, c = t;
 }
 printf("%5.2f,%5.2f,%5.2f\n", a, b, c);
 return 0;
}

 

 

#include<stdio.h >
int main()
{
 int a, b, c, max;
 scanf_s("%d%d%d", &a, &b, &c);
 if (a > b)
  if (a > c)
   max = a;
  else
   max = c;
 else
  if (b > c)
   max = b;
  else
   max = c;
 printf("max=%d\n", max);
 return 0;
}