Get another grade and increment the grade counter
(Display Listing 7.)
After adding the grade to the sum, the code in the body of the loop solicits another grade from the user.
When the user enters the new grade (or -1), the code in the body of the loop increments the variable named count.
This variable keeps track of the number of actual grades entered.
Control then transfers control back to the conditional clause at the top of the loop.
The value of count was also initialized to zero when the variable was declared.