if else statement, sample programs, program to try

If–Else Statement

It is a decision-making statement in the C programming language which allows the program to test for one or more conditions (Boolean value) and execute a set of statements depending on the condition.

  • The statements in the if block are executed if the condition evaluates to true.

  • If the condition is false, the statements in the else block are executed.

Syntax:

if (condition)
{
    statements in if block
}
else
{
    statements in else block
}
  


Note

  • In C, zero and null values are treated as false.

  • Any non-zero or non-null value is treated as true.

  • The else part is optional.

Example

#include<stdio.h>

int main()
{
    int num;
    printf("Enter a number \n");
    scanf("%d",&num);

    if(num < 10)
    {
        printf("The value is less than 10");
    }
    else
    {
        printf("The value is greater than 10");
    }

    return 0;
}

If…Else If Statement

An if statement can be followed by an optional else if…else statement, which is very useful for testing multiple conditions using a single decision structure.

Important Points

  • An if can have zero or one else, and it must come after any else if blocks.

  • An if can have zero to many else if blocks, and they must come before the else.

  • Once an else if condition succeeds, none of the remaining else if or else blocks will be tested.

Syntax

if(boolean_expression 1)
{
    /* Executes when the boolean expression 1 is true */
}
else if(boolean_expression 2)
{
    /* Executes when the boolean expression 2 is true */
}
else if(boolean_expression 3)
{
    /* Executes when the boolean expression 3 is true */
}
else
{
    /* Executes when none of the above conditions is true */
}

Note

Multiple conditions can also be tested using logical operators:

  • AND (&&)

  • OR (||)

  • NOT (!)

Example

#include<stdio.h>

int main()
{
    int marks;
    printf("Enter marks\n");
    scanf("%d",&marks);

    if(marks > 75)
    {
        printf("First class");
    }
    else if(marks > 65)
    {
        printf("Second class");
    }
    else if(marks > 55)
    {
        printf("Third class");
    }
    else
    {
        printf("Fourth class");
    }

    return 0;
}

Nested If–Else Statement

It is always legal in C programming to nest if–else statements, which means you can use one if or else if statement inside another if or else if statement.

Syntax

The syntax for a nested if statement is as follows:

if(boolean_expression 1)
{
    /* Executes when boolean_expression 1 is true */

    if(boolean_expression 2)
    {
        /* Executes when boolean_expression 2 is true */
    }
    else
    {
        /* Executes when boolean_expression 2 is false */
    }
}
else
{
    /* Executes when boolean_expression 1 is false */
}

Example

#include<stdio.h>

int main()
{
    int num;
    printf("Enter a number\n");
    scanf("%d",&num);

    if(num < 10)
    {
        if(num == 1)
        {
            printf("The value is:%d\n", num);
        }
        else
        {
            printf("The value is greater than 1");
        }
    }
    else
    {
        printf("The value is greater than 10");
    }

    return 0;
}

Summary

  • Decision-making or branching statements are used to select one path based on the result of an evaluated expression.

  • They are also called control statements because they control the flow of execution of a program.

  • C provides if and if-else constructs for decision-making statements.

  • We can nest if-else within one another when multiple paths must be tested.

  • The else-if ladder is used when we need to check several conditions based on the result of an expression.


Sample Programs


Check whether the given number is even or odd.
#include <stdio.h>
main()
{
long int n;
system("clear");
printf("Enter the number\n");
scanf("%ld",&n);
if(n%2==0)
  {
  printf("the number is even\n");
  }
else
  {
  printf("the number is odd\n");
  }
}
Check whether the given character is vowel or not
#include <stdio.h>
main()
{
char c;
system("clear");
printf("Enter a character\n");
scanf("%c",&c);
if(c=='a' || c=='e' || c=='i' || c=='o'||c=='u')
  {
  printf("vowel character\n");
  }
else
  {
  printf("not vowel\n");
  }
 }
 Read length of 3 sides and check whether it forms a triangle.
#include <stdio.h>
main()
{
int a,b,c;
system("clear");
printf("Enter three sides \n");
scanf("%d%d%d",&a,&b,&c);
if(a+b>c && b+c >a && a+c >b)
  {
  printf("the sides will form a triangle\n");
  }
else
  {
  printf("cannot form a triangle\n");
  }
}
check the quadrant of given point
#include <stdio.h>
main()
{
int x,y;
system("clear");
printf("Enter the point\n");
scanf("%d%d",&x,&y);
if(x>0 && y>0)
  {
  printf("first qudrant\n");
  }
else if ( x<0 && y>0 )
  {
  printf("second qudrant\n");
  }
 else if (x<0 && y<0 )
  {
   printf("third qudrant\n");
   }
 else if ( x>0 && y <0 )
 {
   printf("fourth quadrant\n");
 }
else
    {
   printf("the point is at origin\n");
     }
}

biggest of 3 numbers
#include <stdio.h>
main()
{
int a,b,c;
system("clear");
printf("Enter three numbers\n");
scanf("%d%d%d",&a,&b,&c);
if(a>b && a>c)
 { printf("biggest=%d\n",a);}
else if(b >a && b >c)
  {printf("biggest=%d\n",b);}
else
  {printf("biggest=%d\n",c);}
}
 
Roots of a quadratic equation/
The standard form of a quadratic equation is:

ax^2 + bx + c = 0, where
a, b and c are real numbers and
a != 0

The term b^2-4ac is known as the discriminant of a quadratic equation. It tells the nature of the roots.

    If the discriminant is greater than 0, the roots are real and different.
    root1=(-b+sqrt(discriminant))/(2*a) root2=(-b-sqrt(discriminant))/(2*a)

    If the discriminant is equal to 0, the roots are real and equal.
    root1=-b/(2*a) root2=-b/(2*a)

    If the discriminant is less than 0, the roots are complex and different.
    realpart=-b/(2*a) imagpart=sqrt(-discriment)/(2*a)
    root1=realpart+imagpart i  root2= realpart+ imagpart i
*/
#include <math.h>
#include <stdio.h>
int main() {
    double a, b, c, discriminant, root1, root2, realPart, imagPart;
    printf("Enter coefficients a, b and c: ");
    scanf("%lf %lf %lf", &a, &b, &c);

    discriminant = b * b - 4 * a * c;

    // condition for real and different roots
    if (discriminant > 0) {
        root1 = (-b + sqrt(discriminant)) / (2 * a);
        root2 = (-b - sqrt(discriminant)) / (2 * a);
        printf("root1 = %.2lf and root2 = %.2lf\n", root1, root2);
    }

    // condition for real and equal roots
    else if (discriminant == 0) {
        root1 = root2 = -b / (2 * a);
        printf("root1 = root2 = %.2lf;\n", root1);
    }

    // if roots are not real
    else {
        realPart = -b / (2 * a);
        imagPart = sqrt(-discriminant) / (2 * a);
        printf("root1 = %.2lf+%.2lfi and root2 = %.2f-%.2fi\n", realPart, 
         imagPart,           realPart, imagPart);
    }

    return 0;
} 
Write a C program that reads employee's ID, name, status (‘F’ for full-time and ‘P’ for part-time) and basic pay. DA and HRA for full-time employees are 75% and 10% of basic pay respectively. Part-time employees have basic pay only. Print the total salary of the employee. ( university question)
#include <stdio.h>
int main() {
    int emp_id;
    char emp_name[50];
    char status;  // 'F' for Full-time, 'P' for Part-time
    float basicPay, totalSalary;

    // Taking employee details as input
    printf("Enter Employee ID: ");
    scanf("%d", &emp_id);

    printf("Enter Employee Name: ");
    scanf(" %[^\n]", emp_name);  // Reads full name with spaces

    printf("Enter Employee Status (F for Full-time, P for Part-time): ");
    scanf(" %c", &status);

    printf("Enter Basic Pay: ");
    scanf("%f", &basicPay);

    // Calculate total salary based on status
    if (status == 'F' || status == 'f') {
        totalSalary = basicPay + (0.75 * basicPay) + (0.10 * basicPay); // DA = 75%, HRA = 10%
    } else {
        totalSalary = basicPay;  // Part-time employees get only basic pay
    }

    // Display the result
    printf("\nEmployee Details:\n");
    printf("ID: %d\n", emp_id);
    printf("Name: %s\n", emp_name);
    printf("Status: %s\n", (status == 'F' || status == 'f') ? "Full-time" : "Part-time");
    printf("Total Salary: %.2f\n", totalSalary);

    return 0;
}



Try the following program using if else
1)Compare two numbers( a==b , a>b or b>a)
2)Check whether the given number is even or odd.
3)Find the biggest of 3 numbers(use if else if)
4)Read internal marks( out of 50) and external mark( out of 100) and print passed /failed in internal or external or failed in both.( use KTU criteria..45% for pass)
5)Check whether the given number is zero, positive or negative.
6)Find the roots of a quadratic equation ( ax^2+bx+c)Test the program using the following sets of data:
a  b  c
2 6 l
3 3 0
1 3 1
0 12 -3
3 6 3
2 -4 3
7)Read length of 3 sides and check whether it forms a triangle.
(All you have to do is use the Triangle Inequality Theorem, which states that the sum of two side lengths of a triangle is always greater than the third side. If this is true for all three combinations of added side lengths, then you will have a triangle.)
8)Check the type of a triangle after reading the three sides ( scalene, isosceles, equilateral)
9) Check the type of a triangle after reading the three vertices ( scalene, isosceles, equilateral)

Note:
From the vertices length of the sides can be computed using the distance formulae.
A scalene triangle is a triangle that has three unequal sides.
An isosceles has two equal sides and two equal angles.
An equilateral triangle is a triangle with all three sides of equal length and also has three equal 60 degree angles.

10) Read a mark ( out of 100) and print the corresponding grade.
Percentage Range Grade
>=90 O
>=85 and <90 A+
>= 80 and <85 A
> =70 and <80 B+
> =60 and <70 B
> =50 and <60 C
>=45 and <50 P
<45 F
11) An Employee's total weekly pay equals the hourly wage multiplied by the total hours worked plus any overtime pay.Overtime pay equals the total overtime hours multiplied by 1.5 times the hourly wage.More than 40 hours/week of working time is considered to be overtime.

Write a C Program that takes as inputs hourly wage and total hours worked in the week and displays an employee's total weekly pay.
12)Check whether a given year is Leap Year or not. A year is leap year if following conditions are satisfied
    1) Year is multiple of 400
    2) Year is multiple of 4 and not multiple of 100.
13)Write a program to check the quadrant of a given point(x,y).
14)Write a program to get the absolute value of number without using the abs() function
15)Write a program that accepts the length of three sides of a triangle as input and determine whether or not the triangle is a right triangle
16)Given three points (x1,y1 ) ,(x2,y2) and (x3,y3), check whether they form a triangle.
17.Check whether the given character is upper case or lower case.
18.Check whether a number is divisible by 3 and 5.Program must produce the following output ( use if else if)
  output: divisible by 3 and 5
               divisible by 3 only
               divisible by 5 only
               not divisible by 3 and 5
19.Find the biggest of 3 numbers ( use nested if)
20.Read the age and print the following ( use nested if)
age <18 Minor
age >=18 and age <45 eligible for vaccine in the second phase
age >=45 senior ..eligible for vaccine in the first phase.
        

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