Why is the operator input prompt displayed twice in my program?

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1 
I'm having an issue with my C program. It's supposed to ask for an operator input once, but instead it shows up twice. Here is a revised version of my code:

int main() {
    char op;
    int apple, banana, carrot;
    int running = 1;

    while (running) {
        printf("Enter operation: ");
        op = getchar();
        switch (op) {
            case 'x':
                printf("Enter apple weight: ");
                scanf("%d", &apple);
                break;
            case 'y':
                printf("Enter banana weight: ");
                scanf("%d", &banana);
                break;
            case 'z':
                printf("Enter carrot weight: ");
                scanf("%d", &carrot);
                break;
            case 'e':
                running = 0;
                break;
        }
    }
    return 0;
}

When I run this, the prompt 'Enter operation:' appears twice. I expected the break to return directly to the start of the next loop iteration where the prompt is printed once. Any suggestions on what might be wrong? I'm still learning C, so I might be overlooking a small detail.
2

I’ve run into this exact problem before! The culprit is usually the newline character (‘\n’) that’s left in the input buffer after you press Enter. Here’s what worked for me:

Add a space before the %c in scanf:

printf("Enter operation: ");
scanf(" %c", &op);

This little space tells scanf to ignore any whitespace (including newlines) before reading the character. It’s a simple fix that solved my double prompt headache.

Another trick I learned is to use fflush(stdin) after getchar(), but it’s not standard C and might not work on all systems. The scanf method is more reliable in my experience.

Hope this helps! Keep coding and don’t let these small hiccups discourage you.

3

The issue you’re encountering is likely due to the newline character left in the input buffer after getchar(). When you press Enter after inputting the operation, it’s read as another input in the next iteration.

To fix this, you can add a line to clear the input buffer after getchar():

op = getchar();
while (getchar() != '\n');

This will consume any remaining characters in the buffer, including the newline. Alternatively, you could use scanf(" %c", &op) with a space before %c to skip whitespace:

scanf(" %c", &op);

Either method should resolve the double prompt issue. Remember to always handle input carefully in C to avoid unexpected behavior.

4

Hey there! looks like ur getchar() is catching the newline char too. quick fix: add getchar() after ur op = getchar() line to eat up that pesky newline. should stop the double prompt. good luck with ur program!