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.

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
```

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.

**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**.

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

Sum = 1275