getchar()

I've got a simple program which asks users for a number 1- 10 and then checks if its a digit or not. At the end I want to prompt the user if they want to continue or exit
and if they want to continue I want to go back to the top.

I put the user's data in an array called c[i] for each character using getchar() and a
loop.

I've read that to clear the input buffer I need to do something like:

while( (d = getchar()) && d != '\n' && d != EOF)
d = getchar;

Problem, input buffer doesn't get cleared. If it put another clear buffer at the top then the user must hit enter but they don't know that.


insert

Code:

---

int main()
{
 
   
    int i, j;
    char c[100];
    int lengthOfInput = 0;
    char d = 0;
   
    j = 0;
   
    while ( j == 0 )
    {

    // initialize array
   
    for (i = 0; i <= 100; ++i)
    {
        c[i] = '\0';
    }
   
    /* Ask for input */
    printf("Enter a number from 1-10.\n");
    for (i = 0; c[i - 1] != '\n'; ++i) {
        c[i] = getchar();
        lengthOfInput += 1;
    }
   
   
    /* Take care of 10 */
    if (((lengthOfInput-1) == 2) && (c[0] == '1') && (c[1] == '0'))
        printf("\'10 divided by 25 is %.1f'\n", 10.0/25.0);
    else if ((lengthOfInput-1) == 1)
    { 
        if (isdigit(c[0]))
        {
            switch(c[0])
            {
                   
                case '4':
                    printf("You chose %c. 4 + 10 is %d.\n", c[0], 4 + 10);
                    break;
                default:
                    printf("You chose %c.\n", c[0]);
                    break;
            }
        }
        else
        {
            printf("Not a valid digit\n");
        }
    }
    else
        printf("Not a valid digit 2.\n");
       
       
        printf("Hit 0 to continue\n");
       
        while ((d = getchar()) && d != '\n' && d != EOF) {
            d = getchar();
            if (d != '0')
                j = 1;
        }
    }
   
   
}

---

Code:

---

// wrong
while( (c = getchar()) && c != '\n' && c != EOF)
c = getchar;


// better
while( (c = getchar()) && c != '\n' && c != EOF)
c = getchar();

---

You need to watch your compiler's warnings and errors... it should have complained about the missing brackets.


And here's a little trick for you... If you use scanf() instead of getchar(), you can tell it to ignore "whitespace" (spaces, tabs, \n, etc) in the buffer like this...

Code:

---

scanf (" %c", &charvar);

---

Note the space between the " and % ...

Yes, you are right, it would complain. I typed it in wrong. In the code I had it right.

@bbray,

Since you declared d as a char type variable, you ought to read this.

Quote:

---

Originally Posted by kermit

@bbray,

Since you declared d as a char type variable, you ought to read this.

---

Thanks! I went back to the drawing board(mostly) and implemented the change you pointed out. It works!!

Here's my new program.

Code:

---


#include <stdio.h>
#include <ctype.h>


int main ()
{

    int c, i, count, tenCheck, e;
    char number[10];
    char d;
   
    d = '1';
    while (d == '1')
    {
       
   
    /* Initialize array */
    for (i = 0; i < 10; ++i)
    {
        number[i] = 0;
    }
   
    /* Get number */
    i = 0;
    count = 0;
    printf("Enter a number between 1 and 10\n");
    while ((c = getchar()) && c != EOF && c != '\n') // Clear input buffer in case of previous iteration
    {
        number[i] = c;
        ++count;
        ++i;
    }
       
    /* Check if 10 was chosen */
    tenCheck = 0;
    if ((count == 2) && (number[0] == '1') && (number[1] == '0'))
    {
        printf("10 divided by 25 is %.1f\n", 10.0/25.0);
        ++tenCheck;
    }
    if (tenCheck == 0)
    {
    /* Check for digit */
    e = 0; // Initializes case if '0' is chosen
    for (i = 0; i < count; ++i)
    {
        if ((count == 1) && (isdigit(number[0])))
        {
            switch (number[i])
            {
                case '4':
                    printf("4 + 10 is %d\n", 4+10);
                    break;
                case '0':
                    printf("You entered \'0\'.\n");
                    printf("Try again.\n");
                    e = 1;
                    break;
                default:
                    printf("You chose %c.\n", number[i]);
                    break;
            }
        }
        else
            printf("Not a digit\n");
       
    }
    }
    /* Check if zero was entered, if so re-run program */
    if (e == 1)
    {
        d = '1';
    }
    else
    {
        /* Prompt if user wants to run again or not */
        c = 0;
        printf("\nEnter 1 to continue, enter any other key to end.\n");
        while ((c = getchar()) && c != EOF && c != '\n')
        {
            d = c;
        }
    }
    }
       
}

---