Two Pseudocode examples with While loops

Problem:
Design an algorithm that will prompt for and receive prices of several items. After the last price is entered, the sentinel amount of –1 is entered. The algorithm should calculate the number of items purchased, total cost of the purchase before tax and with the tax of 7.5%, and display the results on the screen.

A. Defining diagram:

|Input |Processing |Output |
| |Prompt for prices | |
|price |Get all prices |num_items |
|(several prices) |Calculate num_items |cost |
| |Calculate total_cost |tax |
| |Calculate cost and tax |total_cost |
| |Display num_items | |

B. Solution algorithm: (with a sentinel-controlled loop)

Calculating_Cost 1. set num_items to zero, cost to zero // this is a MUST. Why? 2. prompt for price //need to initialize price get price //before checking it in WHILE 3. WHILE price is NOT –1 4. cost = cost + price //this accumulates all prices 5. add 1 to num_items //keeps track of number or items 6. prompt for price get