C - Part 67

Calculate Area of a Circle using math.h library: C

We can calculate area of circle if we know the value of its radius. So using that, we shall write the logic in c program to calculate the area of a circle, and we will us math.h library functions in this program.

Related Read:
Basic Arithmetic Operations In C

 
#include < stdio.h >
#include < math.h >

int main()
{
    float radius;

    printf("Enter radius of circle\n");
    scanf("%f", &radius);

    printf("Area of circle is %f \n", (M_PI * pow(radius, 2)));

    return 0;
}

Output:
Enter radius of circle
2.0
Area of circle is 12.566371

Scanf(): For user input

In above c program we are asking user to enter the values for variable a and b. You can know more about scanf() method/function in this video tutorial: Using Scanf in C Program

Calculate Area of a Circle using math.h library: C

[youtube https://www.youtube.com/watch?v=eTfQ6AmwGow]

YouTube Link: https://www.youtube.com/watch?v=eTfQ6AmwGow [Watch the Video In Full Screen.]

math.h library file has a constant M_PI which has the value of PI. Since it’s a constant variable we can not change its value in our program. We’re also using pow() method/function present in math.h header file.

Formula for calculating Area of a circle

Formula for calculating Area of a circle is PI * radius * radius. We take value of radius from user and using above formula calculate area of the circle and output result to the console window. Since we’re using math.h library file we use M_PI and pow() methods for the expression.

i.e., area = M_PI * pow(radius, 2);

For full C programming language free video tutorial list visit:C Programming: Beginner To Advance To Expert

Calculate Area of a Circle without using math.h library: C

We can calculate area of circle if we know the value of its radius. So using that, we shall write the logic in c program to calculate the area of a circle, without using math.h library functions.

Related Read:
Basic Arithmetic Operations In C

 
#include < stdio.h >

int main()
{
    float radius;
    const float PI = 3.14;

    printf("Enter the value for radius \n");
    scanf("%f", &radius);

    printf("Area of the circle is %f\n", (PI * radius * radius));

    return 0;
}

Output:
Enter the value for radius
5.0
Area of the circle is 78.500003

Scanf(): For user input

In above c program we are asking user to enter the values for variable a and b. You can know more about scanf() method/function in this video tutorial: Using Scanf in C Program

Calculate Area of a Circle without using math.h library: C

[youtube https://www.youtube.com/watch?v=9-_G0N4HnLc]

YouTube Link: https://www.youtube.com/watch?v=9-_G0N4HnLc [Watch the Video In Full Screen.]

Whenever we declare and initialize a constant, its a convention to make use of capital letter variable. That way we can easily spot and identify a constant in our program. And as we already know, value of constant can not be changed through out the program execution.
Ex: const float PI = 3.14;

Formula for calculating Area of a circle

Formula for calculating Area of a circle is PI * radius * radius. We take value of radius from user and using above formula calculate area of the circle and output result to the console window.

Note that we’ve not used math.h library and any of its methods/functions in our program.

For full C programming language free video tutorial list visit:C Programming: Beginner To Advance To Expert

Swap 2 numbers using Multiplication and Division: C

In this video tutorial we shall learn how to swap two integer numbers without using a temporary variable and by simply making use of multiplication and division.

 
#include < stdio.h >

int main()
{
    int a, b;

    printf("Enter 2 integer numbers\n");
    scanf("%d %d", &a, &b);

    printf("You entered a = %d and b = %d\n", a, b);

    a = a * b;
    b = a / b;
    a = a / b;

    printf("After swapping a = %d and b = %d\n", a ,b);

    return 0;
}

Output:
Enter 2 integer numbers
3
5
You entered a = 3 and b = 5
After swapping a = 5 and b = 3

Scanf(): For user input

In above c program we are asking user to enter the values for variable a and b. You can know more about scanf() method/function in this video tutorial: Using Scanf in C Program

Swap 2 numbers using only Multiplication and Division: C

[youtube https://www.youtube.com/watch?v=AcMEvVD0D4U]

YouTube Link: https://www.youtube.com/watch?v=AcMEvVD0D4U [Watch the Video In Full Screen.]

Swapping 2 Numbers In C using only Multiplication and Division: Logic

In our above program we are asking user to enter integer value for a and b.
If the user enters 10 and 5 for a and b respectively. Then our program executes below logic to swap the values of variable a and b.

Step 1: Multiply values of a and b and store it in variable a.
i.e.,
a = a * b;
50= 10 * 5;
So a = 50;

Step 2: Now divide value of b from value of a and store it in variable b.
i.e.,
b = a / b;
10= 50 / 5; (value of a = 50 according to Step 1)
So value of variable b is now 10.

Step 3: Now divide value of b from value of a and store it in variable a.
i.e.,
a = a / b;
5= 50 / 10; (Value of a = 50 from Step 1, and Value of b = 10 from Step 2)
Now the value of a = 5;

Finally value of a = 5(from step 3) and value of b = 10(from step 2).

This is how we swap the value of variable a and b by just making use of multiplication and division in C programming language.

For full C programming language free video tutorial list visit:C Programming: Beginner To Advance To Expert

Swap 2 numbers using Addition and Subtraction: C

In this video tutorial we shall learn how to swap two integer numbers without using a temporary variable and by simply making use of addition and subtraction.

 
#include < stdio.h >

int main()
{
    int a, b;

    printf("Enter 2 integer numbers for, a and b\n");
    scanf("%d %d", &a, &b);

    printf("You entered a = %d and b = %d\n", a ,b);

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

    printf("After swapping a = %d, b = %d\n", a, b);

    return 0;
}

Output:
Enter 2 integer numbers, for a and b
30
20
You entered a = 30 and b = 20
After swapping a = 20, b = 30

Scanf(): For user input

In above c program we are asking user to enter the values for variable a and b. You can know more about scanf() method/function in this video tutorial: Using Scanf in C Program

Swap 2 numbers using only Addition and Subtraction: C

[youtube https://www.youtube.com/watch?v=mm4XJ2DEVS4]

YouTube Link: https://www.youtube.com/watch?v=mm4XJ2DEVS4 [Watch the Video In Full Screen.]

Swapping 2 Numbers In C using only addition and subtraction: Logic

In our above program we are asking user to enter integer value for a and b.
If the user enters 30 and 20 for a and b respectively. Then our program executes below logic to swap the values of variable a and b.

Step 1: Add values of a and b and store it in variable a.
i.e.,
a = a + b;
50 = 30 + 20;
So a = 50;

Step 2: Now subtract value of b from value of a and store it in variable b.
i.e.,
b = a – b;
30= 50 – 20; (value of a = 50 according to Step 1)
So value of variable b is now 30.

Step 3: Now subtract value of b from value of a and store it in variable a.
i.e.,
a = a – b;
20= 50 – 30; (Value of a = 50 from Step 1, and Value of b = 30 from Step 2)

Finally value of a = 20(from step 3) and value of b = 30(from step 2).

This is how we swap the value of variable a and b by just making use of addition and subtraction in C programming language.

For full C programming language free video tutorial list visit:C Programming: Beginner To Advance To Expert

Swap 2 Numbers Without Using a Temporary Variable: C

Today lets learn how to swap 2 integer numbers without using a temporary variable in C. We’re using arithmetic operation in our logic. We’re using addition and subtraction in this c program to swap the 2 numbers.

 
#include < stdio.h >

int main()
{
    int x = 10, y = 5;

    printf("Before swapping x = %d and y = %d\n", x, y);

    x = x + y - ( y = x );

    printf("After swapping x = %d and y = %d\n", x, y);

    return 0;
}

Output:
Before swapping x = 10 and y = 5
After swapping x = 5 and y = 10

Swap 2 Numbers Without Using a Temporary Variable: C

[youtube https://www.youtube.com/watch?v=tTzdGK5t-X4]

YouTube Link: https://www.youtube.com/watch?v=tTzdGK5t-X4 [Watch the Video In Full Screen.]

Swapping 2 Numbers In C using addition, subtraction and assignment operators: Logic

Here we take 2 variables, x and y; We store 10 in x and 5 in y.

We add the values of x(10) and y(5) and then subtract the value returned when we assign x value to y.

Note: When we assign a value to a variable, the same value is returned.
Ex: temp = (a = 10);
In this statement, when we assign 10 to a, the whole expression returns 10 and we can store it in variable temp, for our reference.