Having trouble with scanf function

This is a discussion on Having trouble with scanf function within the C Programming forums, part of the General Programming Boards category; Here are two functions for a simple program. I am trying to get information from the keyboard but for some ...

  1. #1
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    Nov 2001
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    Having trouble with scanf function

    Here are two functions for a simple program. I am trying to get information from the keyboard but for some reason the program does not take the info. In the Get_ballance function no matter what number is entered inD, and ballance ==0. For the Get_Trans function the program does not even pause for input and returns back to main.

    Thanks in advance,
    O'D

    The rest of the file is attached in case you need to look at it.




    /*------------------------------------------------------------------------------------------*/

    void Get_Ballance (double *Ballance)
    {
    double inD=0; /*temp variable*/
    printf("Enter the begining ballance: ");
    scanf ("%f",&inD);
    printf("%4.2f",inD);

    *Ballance = inD;

    /*test*/printf("\n Ballance = ");
    printf("%4.2f",*Ballance);
    printf("\n InD= ");
    printf("%4.2f",inD);

    }

    /*-------------------------------------------------------------------------------------------*/
    void Get_Trans (char *code,double *amount)
    {
    char inC;
    double inD;

    printf("\nChoose from the following options: ");
    printf("\nEnter 'C' for a check. ");
    printf("\nEnter 'D' for a deposit. ");
    printf("\nEnter 'E' to end.");
    scanf ("%c",&inC);
    printf("\n code = ");
    printf("%c",inC);
    }
    Attached Files Attached Files

  2. #2
    and the hat of wrongness Salem's Avatar
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    > scanf ("%f",&inD);
    This should be
    scanf ("%lf",&inD);

    You're reading into a double.

    > For the Get_Trans function
    Before you do this...
    scanf ("%c",&inC);

    Do this
    while ( getchar() != '\n' ) continue;

    So your code looks like this
    while ( getchar() != '\n' ) continue;
    scanf ("%c",&inC);

    Some may tell you to use fflush(stdin), but they are wrong.

  3. #3
    Registered User C_Coder's Avatar
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    aaarrrrggghhh scanf
    the way to use scanf is to not use it. When you use scanf with numbers the newline character is left in the input buffer, so the next time you call scanf it dosent read anything!!!!!
    an alternative is to use fgets followed by sscanf.
    Code:
    char temp[5];
    double InD;
    
    printf("\nEnter a number ");
    fgets(temp, sizeof(temp)-1, stdin);
    sscanf(temp, "%lf", &InD);
    This reads all input out of the input buffer.
    All spelling mistakes, syntatical errors and stupid comments are intentional.

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