C for loop, How do I continuously prompt the user? - c

Question

I am learning about loops such as for and while loops, so I decided to put myself to the test and write a program which you can see the code for below. The program gives the user a range of options to enter an option, but the problem I have is that i want to be able to continuously ask the user to "Enter a command" after an operation has completed.
For example, if I entered 1, the necessary code would be executed but then the whole program just ends. How can I enhance this program so it continuously asks the user to enter new commands until the user forcibly exits by entering 0?
#include <stdio.h>
int main()
{
int n;
int credit = 0;
int YN;
printf("Welcome to Cash booking software Version 2.145\n");
printf("--------------------------------------------------------\n");
printf("Use the following options:\n");
printf("0 -- Exit\n");
printf("1 -- Display Credit\n");
printf("2 -- Change Credit\n");
printf("3 -- Remove Credit\n");
printf("\n");
for ( ; ; )
{
printf("Enter a command: ");
scanf("%d", &n);
if (n == 0)
{
return 0;
}
else if (n == 1)
{
printf("Your credit is £%d", credit);
}
else if (n == 2)
{
printf("Enter a new credit value: \n");
scanf("%d", &credit);
printf("Your new credit value is %d", credit);
}
else if (n == 3)
{
printf("Are you sure you want to remove your Credit value? (Y=1/N=2)");
scanf("%d", &YN);
if (YN == 1)
{
credit = 0;
}
else
;
}
return 0;
}
}

Answer 1

As other users explained return 0; inside of the loop is what is causing the problem and moving it out would solve it, But since you're learning about loops I think this is a great example to teach you something.
Usually you should only use a for loop when you have some parameter that defines de number of times the loop will be executed. The fact that you just used for( ; ; ) is a huge red flag for ther is a betther way to do this.
For example the proper way to write an infinite loop in c is while(1){//code in the loop}. So you could change your for loop with this and it will work fine (relocating return 0; in the correct location).
But since in this code you dont really want an infinite loop (usually they're a bad idea), but you want the loop to run until is pressed 0, the best solution is to use a do{} while(); loop where inside of do you check if either 1, 2 or 3 is pressed and perform their functionality, and then in the while condition you check if 0 has been pressed, and only in that case the program exits.
This is how the code would look like:
do{
printf("Enter a command: ");
scanf("%d", &n);
if (n == 1){
printf("Your credit is £%d\n", credit); // \n added
}
else if (n == 2){
printf("Enter a new credit value: \n");
scanf("%d", &credit);
printf("Your new credit value is %d\n", credit); // \n added
}
else if (n == 3){
printf("Are you sure you want to remove your Credit value? (Y=1/N=2):");
scanf("%d", &YN);
if (YN == 1){
credit = 0;
}
}
} while(n != 0);
return 0;
Also note that I added \n in some printf() commands for better visualization.

Answer 2

use continue statement at the end of each condition , and you can use break statement instead of return 0, so the code will be :
if (n == 0)
{
break;
}
else if (n == 1)
{
printf("Your credit is £%d ", credit);
continue;
}
else if (n == 2)
{
printf("Enter a new credit value: \n");
scanf("%d", &credit);
printf("Your new credit value is %d ", credit);
continue;
}
else if (n == 3)
{
printf("Are you sure you want to remove your Credit value? (Y=1/N=2) : ");
scanf("%d", &YN);
if (YN == 1)
{
credit = 0;
continue;
}
else {
continue;
}