Exercise 3-4: Input to one-dimensional array (array_input.c)

Maximilian Fernaldy - C2TB1702

To repeat an action a certain number of times, we can use the for loop. First we initialize the iterator variable i and set it as 0, then set it to stop before the array length (because the highest index is equal to the array length minus one, due to the array being zero-indexed). Finally in the loop we ask for input from the user, and insert the input into the array with arr[i] = new_entry;.

#include <stdio.h>

#define ARRAY_LENGTH 5

int main() {
    int arr[ARRAY_LENGTH], sum = 0, new_entry;
    for (int i = 0; i < ARRAY_LENGTH; i++) {
        printf("Enter new number into array: ");
        scanf("%d", &new_entry);
        arr[i] = new_entry;
        sum += arr[i];
    }
    
    printf("Your inputs are:\n");
    for (int i = 0; i < ARRAY_LENGTH; i++) {
        printf("arr[%d] = %d\n", i, arr[i]);
    }
    printf("Sum is %d\n", sum);

    return 0;
}

still inside the for brackets, we add the new entry to an accumulating variable sum. After the iterator variable i reaches 5, the condition for the for loop returns False and the loop stops after the fifth iteration. It then continues to execute the code block after the loop, printing the inputs with another for loop and finally printing out the sum of the input numbers. We can see that it also works with negative integers.