C Program 16: To Print The Fibonacci Series Using Recursion

Aim: To print fibonacci series
Fibonacci series is the one in which every third number is the sum of first two.
The series is 1,1,3,4,7,11,18....
//To print the fibonacci series using recursion
#include<stdio.h>
#include<conio.h>
int fibo(int x);
void main()
{
     int a=1, b=1, n,p;
     printf("Enter the number of digits you want to print: ");
     scanf("%d", &n);
     printf("The fibonacci series is:\n%d\n%d", 1 , 1);
     fibo(n);
     getch();
}
int fibo(int x)
{
    static int a =1 , b=1, temp, c;
    if (x-2==0)
    {
               return 0;
    }
    else
    {
        c=a+b;
        printf("\n%d", c);
        temp=b;
        b=c;
        a=temp;
        fibo(x-1); //using recursion
    }
}

The code is fairly simple. We have printed the first two number using a simple printf statement in the main function. Then we have called the fibo()
Now, say we want to print the first 25 numbers in the series. that would mean value of n is 25. But we have already printed first two numbers in main function. So, in the fibo(), in if statement, we would put a condition for x-2 numbers i.e. 23 numbers.
Now, we would use simple arithmetic operation c=a+b; 
This would give us the third number. Then we have performed swapping of the numbers. And then we have called the same fibo() function. 

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C Program 15: To Find the Factorial of a number using for loop

Aim: To find factorial of a number
Factorial of a number like 4 would be 4*3*2*1=24
Following would be the code:
// To find the factorial of a given number using for loop
#include<stdio.h>
#include<conio.h>
void main()
{
     int fact, a;
     printf("Enter the number: ");
     scanf("%d", &a);
     fact=factorial (a);
     printf("The factorial of the given number is: %d\n", fact);
     getch();
     
}
int factorial(int x)
{
    int f=1,i;
    for(i=x; i>=1; i--)
    {
             f=f*i;
    } 
    return f;
}

Just a for loop for(i=x; i>=1; i--) is used. 

In case, you want to do the same through recursion.. check this link:

TO FIND FACTORIAL OF A NUMBER USING RECURSION

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C Program 14: To Find The Factorial of a Number Using Recursion

Aim: To find the factorial using recursion.
What is Recursion? when a function calls itself, the phenomenon is referred to as recursion and it is one of the most powerful features of C. Most of the algorithms that are developed using C use recursion.
Code: 
// To find the factorial of a given number using recursion
#include<stdio.h>
#include<conio.h>
void main()
{
     int fact, a;
     printf("Enter the number: ");
     scanf("%d", &a);
     fact=factorial (a);
     printf("The factorial of the given number is: %d\n", fact);
     getch();
     
}
int factorial(int x)
{
    int f;
    if (x==1)
    {
            return(1);
    }
    else 
    {
         f=x*factorial(x-1); //using recursion
    }
    return f;
}

The real part is in the function factorial. The function takes x as a parameter which is the number whose factorial we want to find. Say, we want to find 4! that means x would be equal to 4.
Now, we would use if else statement. If the value of x is 1, the function would return 1. 
Else, the following formula would be used:
f=x*factorial(x-1);
Note that we are using the same function once again. We are using factorial() inside factorial().  This is RECURSION.
But this time the value passed to the function isn't 4. It is 3 i.e. 4-1
thus, on successive calls the function would call itself and pass parameters like - 4,3,2,1. When function has 1 as parameter, if statement would be executed and control would return to the second last function i.e. the one with parameter 2.
Thus, we would get 4*3*2*1 = 24

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C Program 13: To Swap Two Numbers Using Pointers

Aim: Swap two numbers using pointers.
Following is the code:
//To swap two numbers using pointers
#include<stdio.h>
#include<conio.h>
void swap(int *a, int *b)
{
     int temp;
     temp = *a;
     *a=*b;
     *b=temp;
    // printf ("The value of a is: %d \n ", *a );
     //printf("The value of b is: %d\n ", * b);
}
void main()
{
     int *a, *b;
     printf("enter the two numbers: ");
     scanf("%d%d", &a, &b);
     swap (&a,&b);
     printf ("The value of a is: %d \n", a );
     printf("The value of b is: %d \n ", b);
     getch();
}

Theory: We will perform the swapping in function swap. So, the function swap has two arguments - *a and *b. An * before a means a is actually the value at address of a. So, if the value at address of a is 53, *a would take up that value.
Now, we use the basic swapping operation. We will put the *a into a temporary variable and then *b into *a and again temp into *b. This concludes the swapping. Now, if we want to print the resulting numbers in the swap function itself, we will need to use *a and *b in printf statement instead of a and b. This is because we want to print the value at a and b. If we don't do that, address of the a and b would be printed or some garbage value.
Now, coming back to main function, we must make sure that we pass address of a and b (&a, &b) to the swap function else we won't receive the correct output.

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C Program 12: To Print The Given Rectangle Pattern

Aim: To print this pattern 

*-***********

***-*********

*****-*******

*******-*****

*********-***

***********-*

Code: 

#include<stdio.h>

#include<conio.h>

void main()

{

     int i, j, k;

     for (i=0; i<=5; i++)

     {

         for (j=1; j<=i+(i+1); j++)

         {

             printf("*");

         }

        printf("-");

        for (k=1; k<=11-(i+i); k++)

         {

             printf("*");

         }

         printf("\n"); 

     } 

getch();         

         

}

For this pattern we will need to use three for loops. First loop would be for the number of lines in our pattern. Those are 6 and that's why the condition in the first for loop is i<=5

Now, we will try to divide our pattern in our two parts - one on the left side of dash and other on the right side.

The one at left side is printed in series like 1,3,5,7,9,11. So, all we need to do is to try to use a condition on the second for loop which tries to print this series. This is done through the condition j<=i+(i+1) 

The condition may obviously vary depending upon an individual's logical ability.

Similarly, in the third for loop, we would try to reverse the series - 11,9,7,5,3,1 And hence we will get the desired pattern.

Output: 

In case, you still have doubts.. feel free to contact me. 

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C Program 11: To Print a Right Angled Triangle

Aim:  To print this pattern
*
**
***
****
*****
Code:
#include<stdio.h>
#include<conio.h>
void main()
{
     int i, j, n;
     printf("Click on number of lines you want to print: ");
     scanf("%d", &n);
     for (i=1; i<=n; i++)
      {
               for (j=1; j<=i; j++)
               {
                   printf("*");
               }
               printf("\n");
      }
getch();
}

Theory:  The pattern is the simplest pattern. One thing you should remember while creating patterns is that the first for loop is always for the number of lines you want to cover with your pattern. Here we have asked the user to enter how many lines he wants to print the pattern in.
Then we have used the condition for (i=1; i<=n; i++) to print the stars according to the way we want. The choice is condition depends upon your logical capabilities and may differ.
This is the output:

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C Program 10: To Find The Smallest Number in an Array

Aim: To Find the smallest number in an array
Code:
#include<stdio.h>
#include<conio.h>
void main()
{
     int i, arr[5], smallest;
     printf("Enter the values in an array: ");
     for (i=0; i<=5; i++) /* enter values into array */
     {
         scanf("%d", &arr[i]);
     }
     /* checking the smallest no. */
     smallest = arr[0];
     for (i=0; i<=5; i++)
     {
         if (arr[i] < smallest )
         {
                    smallest = arr[i];
         }
     }
     printf("The smallest number is: %d", smallest);
     getch();
     
}

First we will ask the user to enter the values into the array. Now, we will take an integer smallest and put the initial value of array arr[0] into it.  Now, we have to compare each value present in array with the smallest. If this value is less than the value in  smallest we will replace the value of the latter with the value present in array at that time.

We will repeat that procedure 6 times for our array contains six values.

Following is the sample output:

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C Program 9: To Calculate Sum And Average of Array

Aim: to calculate the sum and average of an array
Theory: We will ask the user to input the values into the array and then we would find out the sum and average.
Following is the code:
#include<stdio.h>
#include<conio.h>
void main()
{
    int arr[5], sum= 0, i=0, j;
    float avg;
    printf("enter the values into the array: ");
    scanf("%d%d%d%d%d%d", &arr[0], &arr[1], &arr[2], &arr[3], &arr[4], &arr[5], &arr[6]);
    printf("The Values you entered are: ");
    for (j=0; j<=5; j++)
    {
        printf("%d\n", arr[j]);
    }
    //finding the sum
    while (i<=5)
    {
          sum = sum + arr[i];
          i++;
    }
    printf("The sum is of the array is: %d \n", sum);
    //finding average
    avg= sum/5;
    printf("The average of the array is: %f", avg);
    getch();
    

}

First, as already mentioned, we would ask the user to input the values into array. One should prefer to use a for loop for the same purpose. However, I have stuck to the very basic form of inputting values into array. Then we will use for loop to print the values entered by the user.
Now, we will find the sum. This is also possible using for loop but we can accomplish this with while loop as well. We can find the sum using this statement sum = sum + arr[i]; 
Once we find the sum, we will display the output. Then we will apply formula for finding the average of an array which is very simple avg = sum/5
This way we will get the following output:

This is a very basic program using arrays. In case, you have any doubts, contact me. 

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C Program 8: To find area of equilateral, isosceles and scalene triangle.

Aim: to find the area of triangle.
Theory: To find area of triangle isn't as simple as it seems to be. There are three kinds of triangles - equilateral (where all sides are equal), isosceles (where two sides are equal) and scalene (where all three sides are of different length).
We will write code to ask the user for what kind of data he has and then on basis of that data we would apply the mathematical formulae.
Here's the code: 

//to find area of all traingles
#include<stdio.h>
#include<conio.h>
#include<math.h>
void isosceles();
void equilateral();
void scalene();
void oneside();
void twosides();
void threesides();
int main()
{
    int type;
    printf("enter the type of traingle:  1 = Isosceles 2=Equilateral 3=scalene :\n ");
    scanf("%d", &type);
    if (type==1)
    {
    isosceles();
    } //calling isosceles function
    else if (type==2)
    {
    equilateral();
    }//calling equilateral function
    else
    {
    scalene();
    } //calling scalene function
    getch();
    return 0;
}
void isosceles() //function1
{
    int choose;
    printf(" choose one option:  1= All sides are known 2= Two sides and one angle is known: \n");
    printf("enter your choice: ");
    scanf("%d", &choose);
    if (choose == 1)
    threesides(); //calling threesides
    else
    twosides(); //calling twosides
   
}
void equilateral() //function2
{
     float root, length, area;
     printf("enter the length of the triangle: ");
     scanf("%f", &length);
     root = sqrt (3);
     area= (root * length *length)/4;
     printf("The area of traingle is: %f", area);
}
void scalene() //function3
{
     int choice;
     printf("Enter your choice: 1= all sides are known \n 2 = Two sides and one angle is known \n 3= One side and two angles are known \n ");
     scanf("%d", &choice);
     if (choice==1)
     threesides();
     else if (choice==2)
     twosides();
     else
     oneside();
}

void oneside() //function4
{
     float angle1, angle2, third_angle, angle4, angle5, angle6, side1, side2, side3, s, areaofthreesides;
     printf("Enter the two angles which are known: ");
     scanf("%f%f", &angle1, &angle2);
   
    third_angle = 180 - (angle1 + angle2);
     //printf("%f", third_angle);
     //finding angles in radian
     //angle4 = (3.14 * angle1)/180;
     //angle5 = (3.14 * angle2)/180;
    //  angle6 = (3.14 * third_angle)/180;
   
     printf("enter the side of the triangle: ");
     scanf("%f", &side1);
   
     //finding other two sides
     side2 = (side1 * sin (angle2))/ sin (angle1);
     side3 = (side2 * sin (third_angle))/ sin (angle2);
   
     //apply formula of calculating area when three sides are given
     s=(side1+side2+side3)/2;
     printf("s = %f", s);
     s = s * (s-side1) * (s-side2)* (s-side3);
     printf("s =: %f", s);
     areaofthreesides = sqrt(s);
     printf("the area of the triangle is: %f", areaofthreesides);
 
}

void twosides() //function5
{
     float side1, side2, angle, angleinradian, area, sines;
     printf("enter the two sides of the triangle: ");
     scanf("%f%f", &side1, &side2);
     printf("enter the angle in degree: ");
     scanf("%f", &angle);
          //finding area
     //angleinradian = (3.14 * angle)/180;
     sines = sin (angle);
     area = (side1 * side2* sines)/2;
     printf("the area of the triangle is: %f", area);
}

void threesides() //function6
{
     float s, areaofthreesides, x, y, z, a, b, c;
     printf("enter the three sides of triangle: ");
     scanf ("%f%f%f", &x, &y, &z);
     s=(x+y+z)/2;
     printf("s = %f", s);
     s = s * (s-x) * (s-y)* (s-z);
     printf("s =: %f", s);
     areaofthreesides = sqrt(s);
     printf("the area of the triangle is: %f", areaofthreesides);
}

Explanation: In main function, we have used conditional statements to check what kind of data is available with the user. According to the input, triangle can be of three types, isosceles, scalene or equilateral.
Isosceles Triangle:
If the user chooses the isosceles triangle option, the control of program would jump to the function isosceles().
There user would be asked if he knows all the sides of the triangle or two sides and one angle? 
If the user chooses the first option, the control goes to the function threesides()
For three sides, we would use the formula which would consist of three parts. 
1. First we will find out s which is equal to (x+y+z/2) where x,y,z, are sides of triangle known to user and entered by him. 
2. then we will calculate s * (s-x) * (s-x) * (s-x) and put the result in s. 
3. Now, we will take square root of the final value in s using the sqrt() function which is used using <math.h> header file.

If the user knows only two sides, then the control would go to twosides() function.
In this function, user would be asked to enter two sides of the triangle and one angle. 
First we would take sine of the angle and use it in main formula - (side1*side2* sines)/2 where sines is the sine of the angle entered by the user.
 Equilateral Triangle
If in first step, user chooses the option with equilateral triangle, control would go to equilateral() function. the formula use here is (squareroot of 3 *length *length) /4 
We will find square root of 3 separately and then use it in this formula.
Scalene Triangle
If user selects option with scalene triangle, the control would go to scalene() function. Here user would be asked if he knows all sides, two sides and one angle or one side and two angles.
On the basis of his choice, control would shift to threesides(), twosides(), oneside() function.
The execution of the first two functions is already discussed. The last function would be executed as follows:
We will first find out the third angle using formula angle1+angle2+angle3 = 180 
Then we will find out other two sides of the triangle using the concept from formula a/sin a1 = b/sin a2 = c/sin a3
where a,b,c are sides of triangle and a1, a2, a3 are three angles of the triangle. Once we find out sides of triangle, we would use the formula same as used in threesides() function.
In case of any doubt, feel free to contact me.. :)

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C Program 7: To find the area and perimeter of rectangle and circumference of circle

Aim: The length & breadth of a rectangle and radius of circle are input through the keyboard. Write a program to calculate the area and perimeter of the rectangle, and the circumference of the circle.

Theory: you need to know about three mathematical formulas and here you go.. This is the code..

//to find area and perimeter of rectangle and circumference of circle

#include<stdio.h>

#include<conio.h>

int main()

{

    int l,b,i;

    float r, area, peri, circum;

    printf("Calculating the area and perimeter of rectangle\n");

    printf("Enter the Length and breadth of rectangle: ");

    scanf("%d%d", &l, &b);

    peri= 2*(l+b);

    area= l*b;

    printf("The area of the rectangle is: %f\n", area);

    printf("The perimeter of the rectangle is: %f\n", peri);

    for(i=0; i<80; i++)

    {

             printf("*");

    }

    printf("\n");

    printf("Calculating the radius of circle\n");

    printf("Enter the radius of the circle\n");

    scanf("%f", &r);

    circum=2*3.14*r;

    printf("The cirumference of the circle is: %f", circum);   

    getch();

    return 0;

}

First we calculated the area and perimeter of rectangle using formulae: 

scanf("%d%d", &l, &b);

peri= 2*(l+b);

Then we calculate the circumference of circle using formula: circum=2*3.14*r;

Ignore the for loop used inside the program. That isn't actually required. I just used it to make the output look more organized.

Here's the output:

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C Program 6: To convert the temperature from Fahrenheit to Celsius.

Aim: Temperature of a city in Fahrenheit degree is input through the keyboard. Write a program to convert this temperature into Centigrade degrees.

Theory: This is one of the basic programs that one should know to make in the C but the only tough part is remembering the formula for conversion of temperature from one scale to another. There is no logic in that. It's just a mathematical formula which you need to keep in mind. The Formula is C= 5(F+32)/9

Code:

//to convert temperature from Fahrenheit to Celsius

#include<stdio.h>

#include<conio.h>

int main()

{

    float fahf, celf;

    printf("Enter the temperature in Fahrenheit: ", fahf);

    scanf("%f", &fahf);

    celf=5*(fahf-32)/9;

    printf("The temperature in Celsius is: %f", celf);

    getch();

    return 0;

}

We just took two variables and then used the formula which I mentioned above in the theory portion. Here's the output:

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C Program 5: To find the average and percentage of marks obtained

Aim: If marks obtained by a student in five different subjects are input through the keyboard, write a program to find out the aggregate marks and percentage marks obtained by the student. Assume that the maximum marks that can be obtained by a student in each subject is 100.

Theory: Again, as in the previous program, this program also needs to basic mathematical formulae.

1. To find the average. The formula is to calculate sum of marks obtained in five subjects/ total number of subject

2. To find the percentage. The formula is to calculate ( the sum of marks obtained*100)/total marks obtained.

The code for this program is:

//to find average and percentage of marks obtained in five subject (out of 100)

#include<stdio.h>

#include<conio.h>

int main()

{

    int a,b,c,d,e;

    float sum,avg, per;

    printf("Enter the marks obtained in five subjects: ");

    scanf("%d%d%d%d%d", &a, &b, &c, &d, &e);

    sum=a+b+c+d+e;

    avg=sum/5; //calculating average marks

    per=sum*100/500; //calulating percentage

    printf("The average marks are:%f\n", avg);

    printf("The percentage is: %f\n", per);

    getch();

    return 0;

}

We asked the user to enter the marks obtained in five subjects. Then we calculate their sum and apply formula for finding average marks obtained and the percentage of the marks obtained. 

The output would be like this:

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C Program 4: To Convert distance in Km to cm, feet, inch and meter.

Aim: the distance between two cities (in km.) is input through the keyboard. Write a program to convert and print this distance in meters, feet, inches and centimeters.

Theory: This program needs no complex coding. It's a simple program where you need to know four basic mathematical formulae. Once you know them, you can easily code this program in C.

Here's the code:

//to convert distance from km to m, cm, feet and inches

#include<stdio.h>

#include<conio.h>

int main()

{

    float km, m, cm, feet, inch;

    printf("Enter the distance in kilometers: ");

    scanf("%f", &km);

    m=km*1000;

    cm=m*100;

    feet=km*3280.8;

    inch=feet*12;

    printf("The distance in meters is %f\n", m);

    printf("The distance in centimeters is %f\n", cm);

    printf("The distance in feet is %f\n", feet);

    printf("The distance in inches is %f\n", inch);

    getch();

    return 0;

}

We used four formulae in the code and calculated the values and then printed the result. That's all. It's too easy. Isn't it?

Here's the snapshot of output:

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C Program 3: To calculate the gross salary when the basic salary is entered through keyboard

Aim: Ramesh's basic salary is input through the keyboard. His dearness allowance is 40% of basic salary, and house rent allowance is 20% of basic salary. Write a program to calculate his gross salary.

Theory: We need to take input from user and then apply the simple formula to calculate the gross salary i.e. gross salary= basic salary+ dearness allowance+ house rent allowance.

Following would be the program code:

//to calculate the gross salary

#include<stdio.h>

#include<conio.h>

int main()

{

    int bs, gs, da, hr;

    printf("Enter the basic salary:");

    scanf("%d", &bs);

    da=40*bs/100; //given that dearance allowance is 40% of basic salaray

    hr=20*bs/100; //given that house rent is 20% of basic salaray

    gs= bs + da + hr; //formula to calculate gross salary

    printf("The gross salary is: %d", gs);

    getch();

    return 0;

}

First we asked the user to enter the basic salary and then take the input using the scanf("%d", &bs); statement. Now, we calculate the dearness allowance using this statement da=40*bs/100; Similary we will calculate the house rent allowance according to the values mentioned in the question and then we would use our main formula to calculate the gross salary  i.e. gs= bs + da + hr; 

Outpur: 

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C Program 2: To Reverse A Number Using An Array

Aim: To reverse a number(digits entered) using an array
Theory: At first, we would need to ask the user about how many digits he is going to enter or what is the length of the number which he wants to reverse. Then we would ask him to enter the digits of the number one by one and then we reverse the digit and print the reverse number.
Following would be the code:
//to reverse the digits in an array
#include<stdio.h>
#include<conio.h>
int main()
{
    int i,j,n,k, a[10];
    a[10]=0;
    printf("enter the number of digits of number you want to reverse: ");
    scanf("%d", &n);
    n=n-1;
    printf("enter the digits one by one: \n");
    for (i=0; i<=n; i++)
    {
        scanf("%d",&a[i]);
    }
 
    for (j=n; j>=0; j--)
    {
        printf("%d", a[j]);
}

    getch();
    return 0;
}


We would use two for loops in the program to accomplish our objective. Before that, we would ask the user to enter the digits he is going to enter. Then, using a for loop, we would get the input one by one. The loop for(i=0; i<=n; i++) serves this purpose.
The next loop with 'j' is used to reverse the number. We use decrement operator in the loop so as to get the number reversed.
What actually happens is, we now print the array from backwards, for eg. when you entered a number 12, the numbers were stored like this in array:
a[0]=1;
a[1]=2;
When you used the decrement counter, you also changed the initialization and condition in the second for loop. The for loop begins with its execution from n, i.e. it first prints a[n] or a[1] in this case.
It works like:
a[1]=2;
a[0]=1;
Thus, the result becomes 21.

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C Program 1: To Print The Sum of First Five Natural Numbers Using Arrays

Aim: To print the sum of first five natural numbers using arrays
Theory: For achieving the desired result, we need to put first five natural numbers in form of array. So, we use a for loop so as to enter the first give natural numbers in an array and then calculate their sum.
The code for the following would be:

//to print the sum of first 5 natural numbers
#include<stdio.h>
#include<conio.h>
int main()
{
    int i,a[10], sum=0;
    for (i=0; i<=4; i++)
    {
        a[i]=i;
        printf("%d\n", a[i]);
        sum=sum+a[i];
     }
     printf("The sum is %d", sum);
    getch();
    return 0;

}


Note that we would initialize the variable for storing the sum to 0. If we don't do that, the sum would initially have a garbage value which would give wrong output.
The first statement a[i]=i;  would allow us to store first five natural numbers in the array form. Then using the next statement, we printed all the first five natural numbers and then we calculate their sum using the statement sum=sum+a[i];
Thus, at the end we get the desired output.

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What To Expect Here?

I knew I could simply start with posting the C Programs which I need to code myself just to increase my efficiency in C programming. In fact, I have already posted a few on PerCepTion which is my personal blog but I felt it would not be a good idea to clutter my personal blog with C Programs. Many of my readers are already disappointed with that move so I decided to make things right and started this one.
So, by now, from the title you can guess that this blog is going to have 100 C Programs which I will be going to code to prepare myself for the campus placement interviews which I am going to have in the month of August.
Till then I intend to post programs here so as to share my work with each one of you who would read this blog.
Well, you might be thinking what's the difference? There are hundreds of blogs which already have this kind of structure and posts; then why should you come here often?
You would see the difference once I will start posting. Not many bloggers explain their code that perfectly which is quite a bad thing. And that's why I felt the need for this..
So stay tuned.. I hope you enjoy visiting this blog :) 

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