Program keeps looping - C++ - c++

Question

The following program does not work properly. It is supposed to be a calculation game which should not loop over and over. I'm not exactly sure what's going on. I tried rearranging some things but that did not help. I noticed that after the user inputs the numbers and answers the question, it just goes to mainMenu even though it should go to display.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
//Declaration Statement
double num1;
double num2;
double answer;
int choice;
void pauseProgram()
{
printf("\nPress any key to continue...");
getchar();
}
//Function Title
void title(char * programTitle)
{
int len = strlen(programTitle);
system("cls");
printf("\n");
for(int i=1; i<40 - len/2;i++) printf(" ");
printf("%s\n",programTitle);
}
void intro()
{
title("Calculation Game");
printf("\nThis program will test your math abilites");
pauseProgram();
}
void userInput()
{
title("Calculation Game");
printf("\nPlease enter positive numbers only\n");
printf("Enter a number:");
scanf("%lf",&num1);
getchar();
printf("Enter another number:");
scanf("%lf",&num2);
getchar();
printf("What is %lf + %lf?",num1,num2);
scanf("%lf",&answer);
if (num1<0 or num2<0)
{
printf("\nSorry, you must enter a positive value! Please try again.");
userInput();
pauseProgram();
}
}
void display()
{
title("Calculation Game");
if (answer=num1+num2)
printf("\nWow you got the right answer\n");
else if (answer!=num1+num2)
printf("\nHmmm...maybe we should review this math concept again!\n");
pauseProgram();
}
void goodbye()
{
title("Calculation Game");
printf("\nFor further information call: 1-800-123-4567\n");
pauseProgram();
}
void mainMenu()
{
title("Calculation Game");
printf("\n1.\tPlay Game");
printf("\n2.\tExit\n");
printf("\nEnter 1 or 2:");
scanf("%d",&choice);
getchar();
if (choice==1)
userInput();
if (choice=2)
goodbye();
if (choice!=1 or choice!=2);
{
printf("\nPlease enter either 1 or 2! Please try again.");
mainMenu();
}
}
//Main program
int main()
{
do
{
intro();
mainMenu();
userInput();
if (answer==num1+num2 or answer!=num1+num2)
{
display();
}
}while(1);
goodbye();
}

Answer 1

As I mentionned in my comment, you can probably see the main() function enters an infinite loop:
do {
...
} while (1)
This loop will not stop until told so. For instance, you can tell the program to exit in your pauseProgram() function :
void pauseProgram()
{
printf("\nPress any key to continue...");
getchar();
exit(0);
}
or in your goodbye() function :
void goodbye()
{
title("Calculation Game");
printf("\nGame designed by David Liubart\n");
printf("\nFor further information call: 1-800-123-4567\n");
pauseProgram();
exit(0);
}
Finally, you could use a break instruction anywhere in the loop in order to exit the loop.