# C Program to find the sum of first 50 natural numbers

For a better understanding, we always recommend you to learn the basic topics of C programming listed below:

In this C program, Here we want to find out the sum of the first 50 natural numbers. For doing this, we have to declare the integer variable 'num, Sum'. And set sum = '0'. By using a For loop  calculate 'sum=sum+num', 50 times. Then display the Sum.

## How to calculate the sum of n natural numbers?

In Mathematics using Arithmetic Progression, we can find out the sum of n numbers by using the formula " Sn = n/2*[2*a+(n-1)*d]". For example, The Sum of 50 natural numbers is,
'S50 = 50/2*[2*a+(50-1)*d]', a is the first term in Arithmetic Progression and 'd' is the common difference of A.P. Here first 'term = a = 1' and Common 'Difference = d = 1'
So

``````
S50 = 25*[2*1+(49)*1]

= 25*[2+49]

= 51*25

= 1275```
```

## What is the syntax of for loop?

In this program, `for loop` is used. The syntax of for loop is given by

``````
for (initializationStatement; testExpression; updateStatement)

{
// codes
}
```
```

Here the initialization statement is executed only once. Initially, evaluate the test expression. If the test expression is False, terminate the for a loop. But if the test expression is True, then run the code inside the `for loop` and update the expression. This process continues until the test expression is False. This type of loop will use only when the number of iterations is finite.

### ALGORITHM

STEP 1: Include the header files to use the built-in header files into the C program.

STEP 2: Declare the integer variables num, Sum, and set sum=0.

STEP 3: Set num=1.

STEP 4: By using the `for loop` with the condition 'num<=50', do step 5.

STEP 5: Calculate sum=sum+num.

STEP 6: Repeat step 4.

STEP 7: Display sum.

## C Source Code

```                                          ```#include <stdio.h>

void main() {
int num, sum = 0;
for (num = 1; num <= 50; num++) {
sum = sum + num;
}
printf("Sum = %d\n", sum);
}```
```

## OUTPUT

`Sum = 1275`
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