Common reason why you would get such an error message despite of no syntax error being spotted after compilation are:
1)you are not passing the memory address of the variable to a scanf statement. for example:
int n;
scanf("%d",n); // wrong statement
scanf("%d",&n);//correct statement
In case of a string ,it is not necessary to place '&' :
char ans[10];
scanf("%s",ans);//correct statement
2)your user defined function is falling into an infinite loop;
void recur(int x)
{
recur(x);
}
3)if you are playing with strings in your code the it is preferable that you use fflush(stdin) after every input statement;
scanf("%s",ans);
fflush(stdin);
