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# Simple interest program in C

Updated on 19/07/20243,840 Views

## Introduction

C is a modern programming language that includes a rich set of built-in functions, data types, and operators. It is a robust language and any complex program can be written by using this language. There are many advantages of using this programming language including its simplicity, fast compilation speed, easy debugging process, quick execution of algorithms, etc. Various types of calculations can be executed by using the C programming language. The application of the C program to calculate simple interest is represented here.

## What is Simple Interest?

The interest amount for a loan or principal amount is known as simple interest. This term is used in various sectors such as banking, automobile, finance, etc. Suppose a person borrows some money from the bank for a specific time period. Here the borrowed money is called the principal amount. While paying back the person must give some extra money apart from the principal amount. This extra money is called simple interest which depends upon the principal amount and the time period. Simple interest is basically the borrowing cost. Here a brief idea about simple interest, its definition, formula to calculate simple interest are represented.

## Formula to Calculate Simple Interest

If the principal amount, rate of interest, and time periods are given then the simple interest is calculated as

Simple Interest (SI) = PTR /100

Here, P = Principal amount

T = Time period (in years) for which the money is borrowed

R = Rate of Interest in percentage

Example:

A person borrows Rs 20000 from the bank for a time period of 1 year. The rate of interest is 20% per annum. Find a simple interest.

Solution:

Here, the principal amount = P = Rs 20000

The time period for which the money is borrowed = T = 1 year

The rate of interest per annum = R =20%

Then simple interest for a year = SI = PTR/100

SI = Rs 4000

The person has to pay an extra amount of Rs 4000 along with the principal amount to the bank at the end of one year.

A simple interest program in C programming is written and explained in the next paragraph.

## Logic used in Simple Interest Program in C language

Here the goal is to calculate simple interest value. So, three types of information are required from the user such as the principal amount, the time period for which the money is borrowed, and the rate of interest per annum. These three values are given as input to the computer and simple interest is the output value. The input values are stored in three variables. Then the formula is applied where the three input variables are multiplied and then divided by 100 to get the required output value i.e. simple interest.

Algorithm to write Simple Interest Program in C Programming

The algorithm used to compute simple interest in C language is presented here.

1. Declare three integer values to store three input variables.

2. The variable P represents the principal amount of money; the variable T represents the time period, and the variable R represents the rate of interest. The variable S represents the simple interest.

3. Declare the output variable as an integer value.

4. Write the formula to calculate a simple interest value where all three input variables are multiplied and divided by 100.

5. Print the output value.

## Simple Interest Program in C Language

// Simple Interest Program in C Language

`# include <conio.h># include <stdio.h># include <stdlib.h>int main(){int P, R, T;int S;printf(â€śEnter the principal amount = â€ť);scanf(â€ś%dâ€ť, &P);printf(â€śEnter the rate of interest = â€ť);scanf(â€ś%dâ€ť, &R);printf(â€śEnter the time period = â€ť);scanf(â€ś%dâ€ť, &T);S = P * R * T Â / 100;printf(â€śThe simple interest is = %dâ€ť, S);return 0;}`

Output:

`After debugging and executing the program the output is represented asEnter the principal amount = 20000Enter the rate of interest = 20Enter the time period = 1The simple interest is = 4000`

Keynotes:

1. Here stdio.h means single input single output. This is a built-in header file in the C programming language. It contains information related to input and output functions.

2. conio.h is a header file and it is used to declare console input-output functions.

3. stdlib.h is a header file that signifies the standard library. This file is used to declare various utility functions for memory allocations, algorithms, etc.

4. int main() function is used as the starting point of program execution. It directs the calls to other functions in the program and thus controls program execution.

5. â€śintâ€ť keyword stands for integer data type and it is used to declare integer value. The format specifier â€ś%dâ€ť is used to display an integer value.

6. printf is an output function that indicates â€śprint formattedâ€ť.

7. scanf is an input function that is used to read input from the user.

According to the formula, three values are calculated and divided by 100 to get the output value. As the output is stored in an integer value, in the result only the integer part will be shown and the decimal part will not be shown. So in order to get a clear and correct result the simple interest program in C using float is represented below.

## Simple Interest Program in C Using Float

// Simple Interest Program in C Language

`# include <conio.h># include <stdio.h># include <stdlib.h>int main(){float P, R, T, S;printf(â€śEnter the principal amount = â€ť);scanf(â€ś%fâ€ť, &P);printf(â€śEnter the rate of interest = â€ť);scanf(â€ś%fâ€ť, &R);printf(â€śEnter the time period = â€ť);scanf(â€ś%fâ€ť, &T);S = (P * R * T) Â / 100;printf(â€śThe simple interest is = %fâ€ť, S);return 0;}`

Output:

`After debugging and executing the program the output is represented asEnter the principal amount = 2022Enter the rate of interest = 15Enter the time period = 1The simple interest is = 303.3`

Keynotes:

1. Float is a datatype used to store floating point numbers. Floating point numbers mean numbers with a decimal point. Format specifier %f is used to declare the floating numbers.

## Simple Interest Program in C Using Function

Given below is the simple interest program in C using function:

`# include <conio.h># include <stdio.h># include <stdlib.h>void simple_interest_calculation (float principal, float rate, float time);int main(){float P, R, T, S;printf(â€śEnter the principal amount = â€ť);scanf(â€ś%fâ€ť, &P);printf(â€śEnter the rate of interest = â€ť);scanf(â€ś%fâ€ť, &R);printf(â€śEnter the time period = â€ť);scanf(â€ś%fâ€ť, &T);simple_interest_calculation (P, R, T)return 0;}void simple_interest_calculation (float principal, float rate, float time);{float S;S = (principal * rate* time)/100;printf(â€śThe simple interest is = %fâ€ť, S);}`

Output:

`After debugging and executing the program the output is represented asEnter the principal amount = 2022Enter the rate of interest = 15Enter the time period = 1The simple interest is = 303.3`

A function is defined as a block of codes and it runs whenever it is called. The set of statements inside the curly bracket is used for the computation part by taking input arguments. The function can be called multiple times.

In this program, a function named simple_interest_calculation is defined. This function takes three arguments named principal which is the principal amount, the rate which is the rate of interest, and time which is the time period. The calculation of simple interest is done by the function named simple_interest_calculation.

In the main function, the user will enter the values of the principal amount, rate of interest, and time period. Then simple_interest_calculation is called with these values as arguments. After that, the function does the simple interest computation and the control again moves back to the main function.

## Conclusion

A clear assessment regarding the calculation of simple interest using C programming is explained here. The simple interest formula is defined and how to calculate it in the C programming environment is shown. Three different programs are depicted by using integer data type, float data type, and function.

## FAQs

1. What is C programming?

C is a modern programming language that includes a rich set of built-in functions, data types, and operators.

2. How to calculate simple interest?

If the principal amount, rate of interest, and time periods are given then the simple interest is calculated as

Simple Interest (SI) = PTR /100

P = Principal amount

T = Time period (in years) for which the money is borrowed

R = Rate of Interest in percentage

3. What is stdio.h?

Here stdio.h means single input single output. This is a built-in header file in the C programming language. It contains the information related to the input and output functions.

4. What is int main ()?

int main() function is used as the starting point of program execution. It directs the calls to other functions in the program and thus controls program execution

5. What is printf?

printf is an output function that indicates â€śprint formattedâ€ť.

6. What is scanf?

Scanf is an input function that is used to read input from the user.

7. What is the meaning of int and float in C programming?

â€śintâ€ť keyword stands for integer data type and it is used to declare integer value. The format specifier â€ś%dâ€ť is used to display an integer value. float is a datatype used to store floating point numbers. Floating point numbers mean numbers with a decimal point. Format specifier %f is used to declare the floating numbers.

8. What is the use of function in C programming?

A function is defined as a block of codes and it runs whenever it is called. The set of statements inside the curly bracket is used for the computation part by taking input arguments. The function can be called multiple times.

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