если я соберу все замечания и многое другое:
#include <stdio.h>
int main()
{
int num;
printf("enter a number less than 10 : ");
if (scanf("%d", &num) != 1)
puts("invalid input");
else if (num < 10)
puts("what an obidient savant you are!");
else
puts("wrong number");
return 0; // may be return an other value on error cases ?
}
Примеры:
pi@raspberrypi:/tmp $ gcc -pedantic -Wall c.c
pi@raspberrypi:/tmp $ ./a.out
enter a number less than 10 : 1
what an obidient savant you are!
pi@raspberrypi:/tmp $ ./a.out
enter a number less than 10 : z
invalid input
pi@raspberrypi:/tmp $ ./a.out
enter a number less than 10 : 20
wrong number