Input looping......it appears once extra time!?

This is a discussion on Input looping......it appears once extra time!? within the C Programming forums, part of the General Programming Boards category; I am doing a program to ask the user to input a char with my menu however,if the user input ...

  1. #1
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    Input looping......it appears once extra time!?

    I am doing a program to ask the user to input a char with my menu

    however,if the user input a invalid char,i have to ask him to input again

    this is a part of my program:
    ==============================================

    do {
    printf("Menu:\n");
    printf("(a) Enter two dates, compute the number of days between them\n");
    printf("(b) Enter a date, return its day of the week\n");
    printf("(c) Enter a month and year, produce a calendar for the month\n");
    printf("(q) Quit\n\n");
    printf("Which one do you want to do (a/b/c/q)? ");
    scanf("%c",&choose);
    } while ((choose!='a')&&(choose!='b')&&(choose!='c')&&(cho ose!='q'));
    ==============================================

    and this is the output:
    ==============================================

    Menu:
    (a) Enter two dates, compute the number of days between them
    (b) Enter a date, return its day of the week
    (c) Enter a month and year, produce a calendar for the month
    (q) Quit

    Which one do you want to do (a/b/c/q)? s <---invalid input
    Menu:
    (a) Enter two dates, compute the number of days between them
    (b) Enter a date, return its day of the week
    (c) Enter a month and year, produce a calendar for the month
    (q) Quit

    Which one do you want to do (a/b/c/q)? Menu:
    (a) Enter two dates, compute the number of days between them
    (b) Enter a date, return its day of the week
    (c) Enter a month and year, produce a calendar for the month
    (q) Quit

    Which one do you want to do (a/b/c/q)?
    ==============================================

    as above,the menu appears once extra time.......

    also,it the user input two char, the menu displays two extra times.....

    what is the method to debug this problem?
    is that my while loop problem?
    Last edited by siumui; 11-15-2002 at 08:38 PM.

  2. #2
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    oh....
    now i understand why it display extra times.....
    thank!


    how do i use fgets() ?
    I am sorry that i am a beginner and actually I don't learn this function yet.....

  3. #3
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    thx you!

  4. #4
    ATH0 quzah's Avatar
    Join Date
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    Or you could just do:

    scanf( "%c%*c", &mychar );

    However, the best way to use scanf is to not use^H^H^H^H^H^H^Hwrite a function that will clear out the input stream when you're done, and call it after scanf.

    Something akin to:

    while(fgetc(stdin)!='\n');


    Quzah.
    Hope is the first step on the road to disappointment.

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