Function to repeat a certain menu in C - c

Question

I am new to C programming language. I want the following code to repeat the main menu after the "Transaction successful" and also store a new balance after an amount is entered.How do i go about it. Here is the code
#include<stdio.h>
int main()
{
int mainmenu, amt, balance = 0;
printf("1.Pay \n");
printf("2.Balance \n");
printf("3.Transaction history \n");
scanf("%d",&mainmenu);
if(mainmenu == 1){
printf("Select Amount \n");
printf("$0.50 \n");
printf("$1.00 \n");
printf("$1.50 \n");
printf("$2.00 \n");
scanf("%d",&amt);
if(amt == 1){
balance = balance + 0.5;
printf("Transaction Successful \n");
}
if(amt == 2){
balance = balance + 1;
printf("Transaction Successful \n");
}
if(amt == 3){
balance = balance + 1.5;
printf("Transaction Successful \n");
}
if(amt == 4){
balance = balance + 2;
printf("Transaction Successful \n");
}
}
if(mainmenu == 2){
printf("\n");
printf("Balance = %d",balance,"\n");
}
if(mainmenu == 3){
printf("No Transaction History At The Moment");
}
}

Answer 1

Simplest way is probably just to use a while loop in this case.
while(1){
//mainmenu here
printf("4. Exit Program");
scanf("%d", &mainmenu);
//if statements/functions here
}
This would require you to add in a fourth option in order to exit out of the while loop, so it doesn't run endlessly (you could also use other methods to know when to exit). A good aspect of this is if they accidentally put in something invalid such as 5 or 7, it doesn't cause any bugs but rather just runs the loop again.
Keep in mind that you'd have to put all your if statements within the while loop, or put them in a different function and call that function after you get the user's input.
P.S. Unrelated but switch statements would probably be a bit easier than if else statements here. They're not necessary but could make your life a little easier.

Answer 2

There are two different methods you can use. A while loop, or a for loop.
The syntax for both are like so:
while(condition) {
statement(s); // execute this section of code until the condition is met
}
and
for (initilization; condition; increment){
statement(s); // execute this section of code until the condition is met
}
if you want an infinite loop, you can use TRUE as the condition in the while loop like:
while(TRUE) {
statement(s); // execute this section of code indefinitely
}
or you can leave the parameters empty in the for loop like so:
for( ; ; ){
statement(s); // execute this section of code indefinitely
}
in your case, it would look like:
#include<stdio.h>
int main()
{
int mainmenu, amt, balance = 0;
while(TRUE){
printf("1.Pay \n");
printf("2.Balance \n");
printf("3.Transaction history \n");
scanf("%d",&mainmenu);
if(mainmenu == 1){
printf("Select Amount \n");
printf("$0.50 \n");
printf("$1.00 \n");
printf("$1.50 \n");
printf("$2.00 \n");
scanf("%d",&amt);
if(amt == 1){
balance = balance + 0.5;
printf("Transaction Successful \n");
}
if(amt == 2){
balance = balance + 1;
printf("Transaction Successful \n");
}
if(amt == 3){
balance = balance + 1.5;
printf("Transaction Successful \n");
}
if(amt == 4){
balance = balance + 2;
printf("Transaction Successful \n");
}
}
if(mainmenu == 2){
printf("\n");
printf("Balance = %d",balance,"\n");
}
if(mainmenu == 3){
printf("No Transaction History At The Moment");
}
}
}
or:
#include<stdio.h>
int main()
{
int mainmenu, amt, balance = 0;
for( ; ; ){
printf("1.Pay \n");
printf("2.Balance \n");
printf("3.Transaction history \n");
scanf("%d",&mainmenu);
if(mainmenu == 1){
printf("Select Amount \n");
printf("$0.50 \n");
printf("$1.00 \n");
printf("$1.50 \n");
printf("$2.00 \n");
scanf("%d",&amt);
if(amt == 1){
balance = balance + 0.5;
printf("Transaction Successful \n");
}
if(amt == 2){
balance = balance + 1;
printf("Transaction Successful \n");
}
if(amt == 3){
balance = balance + 1.5;
printf("Transaction Successful \n");
}
if(amt == 4){
balance = balance + 2;
printf("Transaction Successful \n");
}
}
if(mainmenu == 2){
printf("\n");
printf("Balance = %d",balance,"\n");
}
if(mainmenu == 3){
printf("No Transaction History At The Moment");
}
}
}