Making a menu driven program, errors - c

Question

Beginner to C and doing an assignment for a course. Fixed what I think needed to be fixed, but my menu will only go to part A, but not B, C, or D. It quits fine as well. No errors, wondering what is wrong with my code.
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#define PAUSE system("pause")
#define CLS system("cls")
#define FLUSH flush()
// Prototype Functions Here
void highestNumber(int, int, int);
void lowestNumber(int, int, int);
void displayAverage(int, int, int);
void displayMenu();
void flush();
char getUserChoice();
main() {
char userSelection;
int number1 = 0, number2 = 0, number3 = 0;
do {
userSelection = getUserChoice(); // Gets/DisplaysMenu
switch (userSelection) {
case 'A': // Enter a number
printf("Enter a number 1: ");
scanf("%i", &number1);
printf("Enter a number 2: ");
scanf("%i", &number2);
printf("Enter a number 3: ");
scanf("%i", &number3);
break;
case 'B': // Display Highest Number Entered
printf("In Case B");
highestNumber;
break;
case 'C': // Display Lowest Number entered
printf("In Case C");
lowestNumber;
break;
case 'D': // Display Average of Numbers entered
printf("In Case D");
displayAverage;
break;
case 'Q': // Quit the program
printf("You have quit the program\n");
PAUSE;
break;
default: // Invalid Selection
printf("Invalid selection...try again!\n");
PAUSE;
break;
} // end switch
} while (userSelection != 'Q');
PAUSE;
} // end of main
//==============
void highestNumber(int number1, int number2, int number3) {
if (number1 > number2 && number1 > number3) {
printf("The highest number is: %i", number1);
}
else if (number2 > number1 && number2 > number3) {
printf("The highest number is: %i", number2);
}
else if (number3 > number2 && number3 > number1) {
printf("The highest number is: %i", number3);
}
} //end highest number
void lowestNumber(int number1, int number2, int number3) {
if (number1 < number2 && number1 < number3) {
printf("The lowest number is: %i", number1);
}
else if (number2 < number1 && number2 < number3) {
printf("The lowest number is: %i", number2);
}
else if (number3 < number2 && number3 < number1) {
printf("The lowest number is: %i", number3);
}
} // end lowest number
void displayAverage(int number1, int number2, int number3) {
int average = (number1 + number2 + number3) / 3;
printf("The average of the three numbers you entered is: %i", average);
} // display average
void displayMenu() {
CLS;
printf("\n===============================\n");
printf("========== MAIN MENU ==========\n");
printf("===============================\n");
printf("A. Enter a number\n");
printf("B. Display Highest Number entered\n");
printf("C. Display Lowest Number entered\n");
printf("D. Display Average of Numbers entered\n");
printf("Q. Quit the program\n");
printf("Enter your choice: ");
} // end displayMenu
void flush() {
while (getchar() != '\n');
} // end flush
char getUserChoice() {
char result;
displayMenu();
scanf("%c", &result); FLUSH;
result = toupper(result);
return result;
} // end getUserChoice

Answer 1

the following code should perform as you want.
Caveat: there may be some details that you would like to modify such as uncommenting the calls to getchar()
The following code has a number of constraints built it, like must enter the 3 numbers before trying to do any operations on those numbers.
The following code does not use non-portable calls to the shell.
the data is kept locally in the main() function and passed to each of the sub functions that need it.
Notice the function that changes the data is passed pointers to the data so the sub function can change that data.
useless macros were eliminated
the function: flush() was renamed for clarity as to what it does
appropriate error checking added
commented out unneeded if() statements
expanded flushStdin() to allow for either EOF or '\n'
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
// Prototype Functions Here
void enterNumber (int*, int*, int*); // pass address so function can update
void highestNumber (int, int, int);
void lowestNumber (int, int, int);
void displayAverage(int, int, int);
void displayMenu ( void ); // corrected prototypes
void flushStdin ( void );
char getUserChoice ( void );
int main( void ) // only two valid signatures for main()
// this is one of them
{
char userSelection;
int number1; // added local data variables
int number2;
int number3;
int gotSelections = 0; // so cannot try to work with uninitialized data
do
{
userSelection = getUserChoice(); // Gets/DisplaysMenu
switch (userSelection)
{
case '1': // Enter a number
enterNumber( &number1, &number2, &number3 ); // pass expected parameters
gotSelections = 1;
break;
case '2': // Display Highest Number Entered
if( gotSelections )
{ // then data initialized
highestNumber( number1, number2, number3 ); // pass expected parameters
}
else
{ // else tried to pass unitialized data
printf( "must enter numbers before gathering Statistics\n" );
}
break;
case '3': // Display Lowest Number entered
if( gotSelections )
{ // then data initialized
lowestNumber( number1, number2, number3 ); // pass expected parameters
}
else
{ // else tried to pass unitialized data
printf( "must enter numbers before gathering Statistics\n" );
}
break;
case '4': // Display Average of Numbers entered
if( gotSelections )
{ // then data initialized
displayAverage( number1, number2, number3 );
}
else
{ // else tried to pass unitialized data
printf( "must enter numbers before gathering Statistics\n" );
}
break;
case 'Q': // Quit the program
printf("You have quit the program\n");
//system( "pause" );
break;
default: // Invalid Selection
printf("Invalid selection...try again!\n");
//system( "pause" );
break;
} // end switch
flushStdin();
//getchar();
} while (userSelection != 'Q');
//system( "pause" );
//flushStdin();
getchar();
} // end of main
void enterNumber(int * pNumber1, int *pNumber2, int *pNumber3)
{
printf("Enter a number 1:\n ");
if( 1 != scanf("%i", pNumber1) )
{
fprintf( stderr, "scanf for number1 failed" );
flushStdin();
getchar();
exit( EXIT_FAILURE );
}
printf("Enter a number 2:\n ");
if( 1 != scanf("%i", pNumber2) )
{
fprintf( stderr, "scanf failed for number2" );
flushStdin();
getchar();
exit( EXIT_FAILURE );
}
printf("Enter a number 3:\n ");
if( 1 != scanf("%i", pNumber3) )
{
fprintf( stderr, "scanf for number3 failed" );
flushStdin();
getchar();
exit( EXIT_FAILURE );
}
} //end enter number
void highestNumber(int number1, int number2, int number3)
{
if (number1 > number2 && number1 > number3)
{
printf("The highest number is: %i\n", number1);
}
else if (number2 > number1 && number2 > number3)
{
printf("The highest number is: %i\n", number2);
}
else //if (number3 > number2 && number3 > number1)
{
printf("The highest number is: %i\n", number3);
}
} //end highest number
void lowestNumber(int number1, int number2, int number3)
{
if (number1 < number2 && number1 < number3)
{
printf("The lowest number is: %i\n", number1);
}
else if (number2 < number1 && number2 < number3)
{
printf("The lowest number is: %i\n", number2);
}
else //if (number3 < number2 && number3 < number1)
{
printf("The lowest number is: %i\n", number3);
}
} // end lowest number
void displayAverage(int number1, int number2, int number3)
{
int average = (number1 + number2 + number3) / 3;
printf("The average of the three numbers you entered is: %i\n", average);
} // display average
void displayMenu()
{
//system( "cls" );
puts( "\033[H \033[J"); // \033 is octal value for 'escape'
printf("\n===============================\n");
printf("========== MAIN MENU ==========\n");
printf("===============================\n");
printf("1. Enter a number\n");
printf("2. Display Highest Number entered\n");
printf("3. Display Lowest Number entered\n");
printf("4. Display Average of Numbers entered\n");
printf("Q. Quit the program\n");
printf("Enter your choice: ");
} // end displayMenu
void flushStdin()
{
int ch;
while ( (ch = getchar()) != EOF && '\n' != ch );
} // end flush
char getUserChoice()
{
char result;
displayMenu();
if( 1 != scanf(" %c", &result) )
{
fprintf( stderr, "scanf for menu entry failed" );
flushStdin();
getchar();
exit( EXIT_FAILURE );
}
flushStdin();
//getchar();
result = (char)toupper((int)result);
return result;
} // end getUserChoice