Answer:
The final value of "sum" will be 15, and the program will output:
```
The sum of the first 5 natural numbers is 15
```
You can modify the program to handle different values of "n" by changing the input and displaying appropriate output.
Explanation:
To write a program in QBASIC that inputs a number "n" and prints the sum of the first "n" natural numbers, you can follow these steps:
1. Prompt the user to enter the value of "n" using the INPUT statement.
2. Declare a variable, let's say "sum," to store the sum of the numbers.
3. Initialize the "sum" variable to 0.
4. Use a FOR loop to iterate from 1 to "n" (inclusive).
5. Inside the loop, add the current number to the "sum" variable.
6. After the loop, use the PRINT statement to display the value of "sum."
Here's an example of how the program would look like:
```
INPUT "Enter the value of n: ", n
sum = 0
FOR i = 1 TO n
sum = sum + i
NEXT i
PRINT "The sum of the first", n, "natural numbers is", sum
```
Let's say the user enters the value 5 for "n". The program will calculate the sum as follows:
```
sum = 0
sum = sum + 1 // 1st iteration
sum = sum + 2 // 2nd iteration
sum = sum + 3 // 3rd iteration
sum = sum + 4 // 4th iteration
sum = sum + 5 // 5th iteration
```
The final value of "sum" will be 15, and the program will output:
```
The sum of the first 5 natural numbers is 15
```
You can modify the program to handle different values of "n" by changing the input and displaying appropriate output.