Need help on making a menu system for my program

[Graham93]

I have been given the task to create a system where I have to create a system for conversions which are in four sections weight , measurement , distance and time so for example this would be main page.

Main menu

-----------------------------------------------------------------
Please type the name of the category you would view _

1.Weight
2. Measurement
3.Distance
4.Time
-----------------------------------------------------------------
Then this would go into sub menu. Example if I typed Distance In
-----------------------------------------------------------------
Conversions for Distance

Please type on the conversion you would like to use
1.Mile's to kilometre
2. Kilomere to mile's
3.Main me
-----------------------------------------------------------------
Then you would do the conversion. But I know how I wanted it to layout but I have no idea to start and this menu system
If any one can give some code that will help or a starting point it would be very much appreciated

[Chinchila]

You could use fgets and sscanf to get an input from the user and then do if clauses or switches for the options (As in If (input==1) printf("The menu"), etc...)

[king_zart]

it would be sth like this...

#include <stdio.h>
#include<stdlib.h>
int menu(void);
int distance(void);
 int sw;
int main()
{
    menu();
}


int menu()
{
    system("cls");


 printf(" 1.Weight\n");
 printf(" 2.Measurement\n");
 printf(" 3.Distance\n");
 printf(" 4.Time \n ");
  sw=getch();
  sw=sw-'0';
   switch(sw)
   {
     case 1:
     //code....
     break;


    case 2:
    //...
    break;


    case 3:
    distance();
    break;


    case 4:
    //...
    break;


    default:
    menu();
    break;
   }
}
int distance()
{
    system("cls");
    printf(" 1.Mile's to kilometre\n");
    printf(" 2.Kilomere to mile's\n");
    printf(" 3.Main me\n");
  sw=getch();
  sw=sw-'0';
   switch(sw)
   {
     case 1:
     //code...
     break;


    case 2:
    //code...
    break;


    case 3:
    main();
    break;


    default:
    distance();
    break;
   }
}

[anduril462]

king_zart's solution uses switch statements, which are a great way to handle menu choices, however there are some potential problems with other parts of his program.

The first thing that jumps out is the use of global variables (sw in this case). There are almost always better solutions. Declare the variable in the appropriate function and pass it around as needed. Read this to learn why globals are bad: Global Variables Are Bad.

Second, cls is a Windows specific command, so unless you're using Windows, this wont work. Even if you are, other people may not be, so they can't use it. Plus, many people find it annoying when the terminal keeps clearing itself.

Third, getch() is non-standard function. You could use getchar(), but that comes with it's own set of problems, since if you hit the enter key, it will treat that as a menu choice. scanf("%d", &choice) is one option, though I might use fgets to read a whole line, and sscanf or strtol to parse out the numeric choice.

Lastly, don't use recursion to repeat menus. This can be a problem when your program is used for a long time without ever quitting. What happens is that each function call gets placed on the stack, and they keep piling up because the function never gets a chance to return. Eventually this can cause you program to crash. Instead, I recommend a do loop:

do {
    valid_choice = 1;  // assume user input is valid
    print menu choices
    read input  // set to something invalid like -1, if reading fails
    switch (input) {
        case 1:
            get miles
            convert to km
            print result
            break;
       ...
       case 3:
           break;  // go back to main menu
       default:
           valid_choice = 0;  // bad input
           break;
    }
} while (!valid_input  || input != 3);

Note, depending on whether you read the menu choice as an int or a char, you may need to use case 1: or case '1': (note the single quotes).

[Graham93]

Thank's for everyone's input it helped me alot.

[whiteflags]

I still prefer a menu function though, something like:

function menuChoice:
   display choices
   get a choice
   while choice is not valid:
      display error
      get a choice
   end while
   return choice

It can be really easy to use.

 while ((choice = menuChoice()) != QUIT_CHOICE) ...

[binbag]

Hi I am doing trying to do a conversion code also but cant get the conversions to work properly
I have done a miles to kilometres conversion at the bottom

#include <stdio.h>#include<stdlib.h>


int menu();
int distance();
int sw;
int main()
{
    menu();
    float value;
    value=distance();
    printf("%f", value);
    return 0;


}




int menu()
{
system("cls");


printf(" Please selcet a category\n");
printf(" 1.Weight\n");
printf(" 2.Measurement\n");
printf(" 3.Distance\n");
printf(" 4.Tempereture \n ");
sw=getch();
sw=sw-'0';
switch(sw)
{
case 1:
//code....
break;




case 2:
//...
break;




case 3:
distance();
break;




case 4:
//...
break;




default:
menu();
break;
}
}
int distance()
{
system("cls");
printf(" 1.Miles to kilometres\n");
printf(" 2.Kilomeres to miles\n");
printf(" 3.Return to the Main menu\n");
sw=getch();
sw=sw-'0';
switch(sw)
{
case 1:
MtoK();
break;




case 2:
//code...
break;




case 3:
main();
break;




default:
distance();
break;
}
}
int MtoK()
{
float miles, kilometres;
system("cls");
printf("\t\tMiles to Kilometres Conversion\n");
printf("\t\t------------------------------\n");
printf("\t\tEnter number of Miles: ");
kilometres=miles/0.621371192;


printf("\t\t%2.2f mile(s) == %2.2f kilometre(s)",miles, kilometres);
printf("\n\n\tPress enter to return to the Main Menu");
getchar();
          return kilometres;
}

[Salem]

@binbag - you've got your own thread here -> Help me
No need to hijack someone else's thread, even if you seem to be in the same class, or have the same kind of question.

Though you should really read post #4 to understand why the example you copy/pasted is not the best approach.