c do while loop doesn't work?

do
{
    printf("Enter开发者_运维百科 number (0-6): ", "");
    scanf("%d", &Num);
}while(Num >= 0 && Num <=6);

any ideas?

You're misunderstanding your loop.

Your code is read like this:

Do something While (as long as) num is more than (or equal to) zero And num is less than (or equal to) six

The C compiler is listening to your code and doing exactly what you are (mistakenly) telling it to, which is to keep looping as long as the number is between 0 and 6.

You actually want it to keep looping as long as the number is not between 0 and 6, so you actually want the code to look like this:

Do something While num is less than zero Or num is more than six

Once the user enters a number that is between 0 and 6, the code will see that num is neither less than 0 and nor more than 6, so it will stop the loop. (Because the condition will be false)

You should be able to code that yourself.
Hints: > means 'more than', < means 'less than', and || means 'or'.

It works completely fine for me, as long as Num is declared as an int.

#include <stdio.h>
int main()
{
    int Num;
    do
    {
    printf("Enter number (0-6): ", "");
    scanf("%d", &Num);
    } while(Num >= 0 && Num <=6);

    printf("Done.\n");

    return 0;
}

Did you declare Num as a char, perhaps?

@tom: Here's a sample session with my compiled code; what's different when you run it?

$ gcc a.c && ./a.out
Enter number (0-6): 0
Enter number (0-6): 1
Enter number (0-6): 2
Enter number (0-6): 3
Enter number (0-6): 4
Enter number (0-6): 5
Enter number (0-6): 6
Enter number (0-6): 7
Done.

Maybe you need to add a getchar after scanf to remove '\n' from keyboard buffer:

do
{
    printf("Enter number (0-6): ", "");
    scanf("%d", &Num);
    getchar();
} while(Num >= 0 && Num <=6);

Hope it helps.

This code is working fine with me, I have run your program, user can only enter the values from 0 to 6, do while work in this range, on other values loop break.