# C Program: Calculate sum of Prime numbers with Do-While Loop

## C Do-While Loop: Exercise-9 with Solution

Write a C program that calculates and prints the sum of prime numbers up to a specified limit (e.g., 50) using a do-while loop.

**Sample Solution:**

**C Code:**

```
#include <stdio.h>
int isPrime(int num) {
if (num < 2) {
return 0; // Not a prime number
}
for (int i = 2; i * i <= num; i++) {
if (num % i == 0) {
return 0; // Not a prime number
}
}
return 1; // Prime number
}
int main() {
int limit;
int num = 2; // Starting from the first prime number
int sum = 0;
// Prompt the user to enter a limit
printf("Input the limit for prime numbers: ");
scanf("%d", &limit);
// Calculate and print the sum of prime numbers up to the specified limit
do {
if (isPrime(num)) {
sum += num; // Add prime numbers to the sum
}
num++; // Move to the next number
} while (num <= limit);
// Print the sum of prime numbers
printf("Sum of prime numbers up to %d: %d\n", limit, sum);
return 0; // Indicate successful program execution
}
```

Sample Output:

Input the limit for prime numbers: 50 Sum of prime numbers up to 50: 328

Input the limit for prime numbers: 7 Sum of prime numbers up to 7: 17

**Explanation:**

Here are key parts of the above code step by step:

- int isPrime(int num): Function to check if a number is prime. Returns 1 for prime numbers, 0 otherwise.
- int limit;: Variable to store the user-specified limit.
- int num = 2;: Initializes the variable to start checking prime numbers from 2.
- int sum = 0;: Initializes the variable to store the sum of prime numbers.
- printf("Enter the limit for prime numbers: ");: Prompts the user to enter the limit.
- scanf("%d", &limit);: Reads the user-specified limit.
- do { ... } while (num <= limit);: Do-while loop to calculate the sum of prime numbers up to the specified limit.
- if (isPrime(num)) { sum += num; }: If the current number is prime, add it to the sum.
- num++;: Move to the next number.
- } while (num <= limit);: Continue the loop until the specified limit is reached.
- printf("Sum of prime numbers up to %d: %d\n", limit, sum);: Print the sum of prime numbers.
- return 0;: Indicates successful program execution.

**Flowchart: **

**C Programming Code Editor:**

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