While loop loops infinitely when checking if variable is a digit - c

Question

I'm pretty new to programming so answer to this one might be simple but i can't find it. When checking wether the variable is over 1000 or under 1 the program works but whenever i input a letter the program just loops infinitely. Anyways here's the code and thanks for your help:
printf("Player 1 enter A number between 1 and 1000: ");
scanf("%d", &num);
while(num<1 || num>1000 || !isdigit(num)){
printf("please enter different number: ");
scanf("%d", &num);
}

Answer 1

scanf is a poor choice for reading input from the user.
You probably want this:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>
// Get a number from the user
// number: pointer to the number
// return value: 1 if the user has typed a number
// 0 if the user ha not typed a number
int GetNumber(int *number)
{
char inputbuffer[20];
fgets(inputbuffer, sizeof inputbuffer, stdin); // read raw line from user
if (!isdigit(inputbuffer[0])) // if first char isn't a digit
return 0; // it's not a number, return 0
*number = strtol(inputbuffer, NULL, 10); // convert to number
return 1;
}
int main()
{
int num;
printf("Player 1 enter A number between 1 and 1000: ");
while (!GetNumber(&num) || num < 1 || num > 1000) {
printf("please enter different number: ");
}
printf("number = %d\n", num);
return 0;
}
Alternative version of GetNumber:
int GetNumber(int *number)
{
char inputbuffer[20];
fgets(inputbuffer, sizeof inputbuffer, stdin);
char *endptr;
*number = strtol(inputbuffer, &endptr, 10);
if (*endptr != '\n') // if user input ends with somethign else than
return 0; // \n it's not a number (e.g: "123a")
return 1;
}