Option problem

This is a discussion on Option problem within the C Programming forums, part of the General Programming Boards category; Hello, I'm new to this forum and programming in general,but I'd like to learn,and I already started with C programming. ...

  1. #1
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    Option problem

    Hello, I'm new to this forum and programming in general,but I'd like to learn,and I already started with C programming.

    But in a program I'm recently writing I have a problem.It's a small program,nothing fancy for someone with my level and experience.But I wanted to give the user three options like this:

    1. Option
    2. Option
    3. Option

    And I wondered if you guys can help me out with a code to make any other inputs into the program other then these three options illegal,with a message to please try again from the following options.

    Any ideas?

  2. #2
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    Use switch ,

    Code:
    #include<stdio.h>
    
    main()
    {
            int op;
            printf("Please Enter the option ( 1 / 2 / 3 ) : ");
            scanf("%d",&op);
            switch(op)
            {
                    case 1:
                    printf( "You have entered one \n" );
                    break;
                    case 2:
                    printf( "You have entered two \n" );
                    break;
                    case 3:
                    printf( "You have entered three \n" );
                    break;
                    default:
                    printf( "Invalid option\n" );
            }
    }

  3. #3
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    Thank you.

  4. #4
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    The code is almost what I'm looking for,only with two things missing.

    How do you make the program stop to display the results,because getchar() doesn't seem to work,other then system("pause"),and I read it's not a good idea to use system calls.

    And the other thing is,how could I make the program return to the original options displayed the first time if you hit the wrong key and type "try again"?

  5. #5
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    How do you make the program stop to display the results,because getchar() doesn't seem to work,other then system("pause"),and I read it's not a good idea to use system calls.
    You can either run your program for the console / command-line (where your program will exit, but the output will still be visible) or use a different function at the end. stdio.h provides several functions that require hitting enter before moving on. None of them are completely ideal for that purpose, but at least they're standardized. In the real world, non-GUI programs usually just exit, as they are usually run from the console anyway (or they're intended to just disappear once they're done).

    Having said that about 'real-world' apps, there's nothing THAT wrong with using system("pause") as long as it's just part of a learning exercise, or a program for fun. Just keep in mind that your code won't be portable on other systems, and you might be missing out on a better way to do things.

    And the other thing is,how could I make the program return to the original options displayed the first time if you hit the wrong key and type "try again"?
    Have you learnt about loops yet? A do / while loop would be best. You put your code in the "do" block, and then repeat it while the input is invalid. As soon as they enter something valid, the loop exits.

  6. #6
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    you may use getch() instead of getchar(), getch() is included in conio.h

    example:
    Code:
    #include <stdio.h>
    #include <conio.h>
    
    int main()
    { 
     printf("Press something.\n");
     getch();
     printf("Done something.\n");
     getch();
    
     return 0;
    }
    karthigayan, if you dont mind, i will use your code in this example.
    you should use a WHILE loop in here, here is an example:

    Code:
    #include<stdio.h>
    #include<conio.h>
    
    main()
    {
            int op;
            printf("Please Enter the option ( 1 / 2 / 3 ) : ");
             
            while(op != 1 && op != 2 && op != 3)
            {        
            scanf("%d",&op);
    
            switch(op)
            {
                    case 1:
                    printf( "You have entered one \n" );
                    break;
                    case 2:
                    printf( "You have entered two \n" );
                    break;
                    case 3:
                    printf( "You have entered three \n" );
                    break;
                    default:
                    printf( "Try again\n" );
            }
          }
    }
    if this seems confusing, the != sign means if 'not equal'. so if OP is
    not 1 nor 2 or 3, then that means the user typed an incorrect number
    so the loop keeps going. however, if OP is equal to either 1, 2, or 3
    then the loop exits. simple, eh?

    Cheers, ComputerWarrior.
    Last edited by ComputerWarrior; 08-02-2010 at 11:24 AM.

  7. #7
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    Quote Originally Posted by ComputerWarrior View Post
    you may use getch() instead of getchar(), getch() is included in conio.h

    example:
    Code:
    #include <stdio.h>
    #include <conio.h>
    
    int main()
    { 
     printf("Press something.\n");
     getch();
     printf("Done something.\n");
     getch();
    
     return 0;
    }
    conio.h and getch() are not part of the "standard" language as defined in the C99 standard. Some implementations (compilers and libraries) support them.

    [Edit: Removed comment about now corrected while line.]
    Last edited by pheininger; 08-02-2010 at 02:27 PM. Reason: Original code corrected.

  8. #8
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    sorry 'bout that, i was in a hurry so i must have forgotten the && signs...
    thanks for pointing that out pheininger!

  9. #9
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    Thanks guys,I'm interested in one more thing.I saw on certain programs that you can "refresh" the window from the text,in order to show the next available text or options.Can you guys tell me what code it is?

  10. #10
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    I saw on certain programs that you can "refresh" the window from the text,in order to show the next available text or options.
    I'm not sure what you mean here. You can call fflush() on output streams, which ensures that all text you have asked to be outputted is actually outputted. It's useful for debugging when your program crashes after an output statement before the output is actually performed.

  11. #11
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    It's something to do with what system clearscreen does,but I was wondering if you could advise of a better way of doing it.

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