C programs for If-Else

Programming Practices for If-Else

1. C program to find the greatest number among three numbers :

#include <stdio.h>
int main(void)
{
    int a, b, c;
    printf(" Enter the number1 = ");
    scanf("%d", &a);
    printf("\n Enter the number2 = ");
    scanf("%d", &b);
    printf("\n Enter the number3 = ");
    scanf("%d", &c);
    if (a > b)
    {
        if (a > c)
        {
            printf("\n Greatest number = %d \n",a);
        }
        else
        {
            printf("\n Greatest number = %d \n",c);
        }
    }
    else if (b > c)
    {
        printf("\n Greatest number = %d \n",b);
    }
    else
    {
        printf("\n Greatest number = %d \n",c);
    }
    return 0;
}

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2.C program to find out whether a given year is a leap year or not :

#include <stdio.h>
int  IsLeapYear(int year)
{
    // Function to check leap year.
    if (year % 4 != 0)
        return 0;
    if (year % 100 != 0)
        return 1;
    return (year % 400) == 0;
}
int main()
{
    unsigned int uiYear=0;
    printf("Enter the year:");
    scanf("%u",&uiYear);
    (IsLeapYear(uiYear)? printf("Leap Year."): printf("Not Leap Year."));
    return 0;
}

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3.C program to convert temperature from Fahrenheit to Celsius and Celsius to Fahrenheit :

The basic formula to convert Fahrenheit and Celsius to each other.
Celsius to Fahrenheit: (°C × 9/5) + 32 = °F
Fahrenheit to Celsius: (°F − 32) x 5/9 = °C


#include <stdio.h>
int main()
{
    float fh,cl;
    char ch;
    printf("\n\n Press c to convert temperature from Fahrenheit to Celsius.");
    printf("\n\n Press f to convert temperature from Celsius to Fahrenheit.");
    printf("\n\n Enter your choice (c, f): ");
    scanf("%c",&ch);
    if((ch =='c') ||(ch =='C'))
    {
        printf("\n\nEnter temperature in Fahrenheit: ");
        scanf("%f",&fh);
        cl= (fh - 32) / 1.8;
        printf("\n\nTemperature in Celsius: %.2f\n\n",cl);
    }
    else if((ch =='f') ||(ch =='F'))
    {
        printf("\n\nEnter temperature in Celsius: ");
        scanf("%f",&cl);
        fh= (cl*1.8)+32;
        printf("\n\nTemperature in Fahrenheit: %.2f\n\n",fh);
    }
    else
    {
        printf("\n\nInvalid Choice !!!\n\n");
    }
    return 0;
}
 

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4. C program to check sign of a given number:

The MSB bit of a number defines their sign. If the MSB bit is set, the number will be negative.


#include <stdio.h>
int main()
{
    int sign = 0;
    int data = 0;
    printf("\n\n Enter the number  = ");
    scanf("%d",&data); //Get the number
    sign = (data > 0) - (data < 0); // check the sign of the number
    if(sign == 1)
    {
        printf("\n\n Enter number is a positve number\n");
    }
    else if(sign == -1)
    {
        printf("\n\n Enter number is a negative number\n");
    }
    else
    {
        printf("\n\n Enter number is zero\n");
    }
    return 0;
}

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5.C program to check whether triangle is equilateral, scalene or isosceles:

Before writing the program, we should know the properties of isosceles, equilateral and scalene triangles.

Isosceles triangle: In geometry, an isosceles triangle is a triangle that has two sides of equal length.

Equilateral triangle: In geometry, an equilateral triangle is a triangle in which all three sides are equal.

Scalene triangle: A scalene triangle is a triangle that has three unequal sides.


#include <stdio.h>
int main(void)
{
    int triSide1, triSide2, triSide3;
    /* Get sides of a triangle from the user */
    printf("\n Enter first side of triangle: = ");
    scanf("%d", &triSide1);
    printf("\n Enter second side of triangle: = ");
    scanf("%d",&triSide2);
    printf("\n Enter third side of triangle: = ");
    scanf("%d",&triSide3);
    if((triSide1==triSide2) && (triSide2==triSide3))
    {
        /* If all sides are equal, then Equilateral triangle*/
        printf("\n Equilateral triangle.\n\n");
    }
    else if((triSide1==triSide2) || (triSide1==triSide3) || (triSide2==triSide3))
    {
        /* If two sides are equal, then Isosceles triangle*/
        printf("\n Isosceles triangle.\n\n");
    }
    else
    {
        /* If none sides are equal, then Scalene triangle*/
        printf("\n Scalene triangle.\n\n");
    }
    return 0;
}
 

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6. C program to enter week number and print day of week:

#include <stdio.h>

int main()
{
    /* Declare constant name of weeks */
    const char * WEEKS[] = { "Monday", "Tuesday", "Wednesday", 
                            "Thursday", "Friday", "Saturday", 
                            "Sunday"};
    int week;

    /* Input week number from user */
    printf("Enter week number (1-7): ");
    scanf("%d", &week);
	
    if(week > 0 && week < 8)
    {
        /* Print week name using array index */
        printf("%s", WEEKS[week-1]);
    }
    else
    {
        printf("Invalid input! Please enter week number between 1-7.");
    }

    return 0;
}

*************************************************************************

7.C program to check whether the triangle is valid or not if sides are given:

#include <stdio.h>
int main(void)
{
    int a, b, c, sum; //variable to store angles
    // Get three sides of triangle from the user
    printf("\n Enter 1 side of triangle: = ");
    scanf("%d", &a);
    
    printf("\n Enter 2 side of triangle: = ");
    scanf("%d", &b);
    
    printf("\n Enter 3 side of triangle: = ");
    scanf("%d", &c);
    
    //check validity of triangle
    if((a + b > c) && (a + c > b) && (b + c > a))
    {
        printf("\n Valid triangle.\n\n");
    }
    else
    {
        printf("\n Not valid triangle.\n\n");
    }
    return 0;
}

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8.C program to enter student marks and find percentage and grade:

A college has the following rules for grading system:

1. Below 25 – F
2. 25 to 45 – E
3. 45 to 50 – D
4. 50 to 60 – C
5. 60 to 80 – B
6. Above 80 – A

Ask the user to enter mark of 5 subjects and print the corresponding grade.


#include <stdio.h>
int main(void)
{
    float subMark[5]= {0};
    float per = 0.0;
    int i = 0;
    float sum = 0.0;
    /* Get subject Marks from user */
    for(i=0 ; i <5; i++) { printf("\n Enter subject %d marks: ",i); scanf("%f",&subMark[i]); //check validty of marks if(subMark[i]> 100)
        {
            printf("\n Enter valid number ! \n");
            i--;
        }
        else
            sum  += subMark[i];
    }
    /* total marks */
    printf("\n total marks = %f\n", sum);
    /* Calculate percentage */
    per = (sum / 500.0)*100;
    printf("\n Percentage = %.2f\n", per);
    /*Grade according to the percentage */
    if(per >= 80)
    {
        printf("\n Grade A");
    }
    else if(per >= 60)
    {
        printf("\n Grade B");
    }
    else if(per >= 50)
    {
        printf("Grade C");
    }
    else if(per >= 45)
    {
        printf("\n Grade D");
    }
    else if(per >= 25)
    {
        printf("\n Grade E");
    }
    else
    {
        printf("\n Grade F");
    }
    return 0;
}
 

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9.Write a C program to input basic salary of an employee and calculate gross salary according to given conditions.

Basic Salary <= 10000 : HRA = 20%, DA = 80%
Basic Salary is between 10001 to 20000 : HRA = 25%, DA = 90%
Basic Salary >= 20001 : HRA = 30%, DA = 95%

#include <stdio.h>

int main()
{
    float basic, gross, da, hra;

    /* Input basic salary of employee */
    printf("Enter basic salary of an employee: ");
    scanf("%f", &basic);


    /* Calculate D.A and H.R.A according to specified conditions */
    if(basic <= 10000)
    {
        da  = basic * 0.8;
        hra = basic * 0.2;
    }
    else if(basic <= 20000)
    {
        da  = basic * 0.9;
        hra = basic * 0.25;
    }
    else
    {
        da  = basic * 0.95;
        hra = basic * 0.3;
    }

    /* Calculate gross salary */
    gross = basic + hra + da;

    printf("GROSS SALARY OF EMPLOYEE = %.2f", gross);

    return 0;
}

 

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