I can't understand why input '-' or '+' jump to display no record found.Code:#include <stdio.h>
#include <stdlib.h>
int main()
{
int stop, ch, valid = 0;
do
{
// display title
printf("Individual Salesman Commission\n");
printf("==============================\n");
// prompt and read salesman id
printf("Salesman ID (NO.): ");
scanf("%d", &stop);
// Only give user to pass if it is number
while ( (ch = getchar()) != '\n')
{
// if it is not valid input
if(ch > 1)
{
while ( (ch = getchar()) != '\n');
printf("Invalid input. Please input again...\n");
getchar();
system("cls");
// display title
printf("Individual Salesman Commission\n");
printf("==============================\n");
// prompt and read salesman id
printf("Salesman ID (NO.): ");
scanf("%d", &stop);
} // end if
} // end while
valid = 1; // end loop process
// clear screen display
system("cls");
} while (valid == 0); // loop if the input is invalid
if(stop <= 0 )
{
// Display error message
printf("No record found.\n");
} // end else
printf("Press Enter to exit program...\n");
getchar();
} // end function main