Q.Let us answer the following questions using the pesudocode given in example 4.9:

Example 4.9's pseudocode adds inputs until 0 is entered (0 itself excluded; later values never read).

Trace of 6, 7, 4, 8, 2, 5, 0 (3 and 1 are never read): sum runs 6→13→17→25→27→32, count runs 1…6.

1. sum = 32 (6+7+4+8+2+5; the loop stops at 0, so 3 and 1 are ignored).
2. count = 6.
3. num is input once before the loop (priming read, so the very first value can be tested) and again at the loop's end — this way the sentinel 0 is checked before being added.
4. sum / count is the average — sum holds the total of exactly count numbers. …

The idea. Example 4.9 computes the average of numbers entered until the user types 0 (the sentinel). Its shape: initialise sum and count to 0; INPUT num once; WHILE num ≠ 0 → add num to sum, add 1 to count, INPUT num again; finally average = sum / count. Answering the five questions is a matter of dry-running that pseudocode on the given inputs.

Dry-run for inputs 6, 7, 4, 8, 2, 5, 0, 3, 1:

The 3 and 1 typed after 0 are never read — the algorithm has already left the loop.

1) What will the sum be? 32 (= 6 + 7 + 4 + 8 + 2 + 5). The sentinel 0 adds nothing and stops the loop before 3 and 1.

2) Value of count? 6 — six numbers were processed before the sentinel.

3) Why input num twice? It is the priming read pattern. The first INPUT (before the loop) fetches a value so the WHILE condition has something to test on the very first pass; the second INPUT (at the bottom of the body) fetches the next value so it is tested before being processed. Together they guarantee the sentinel 0 is never added to sum or counted.

4) Why divide sum by count? sum holds the total of exactly count genuine numbers, and average is defined as total ÷ how-many. Dividing by a fixed number (like 5) would be wrong because the user decides how many numbers to enter.

5) Any other approach? Yes, several:

• Count-controlled: first ask "how many numbers?" (n), then loop exactly n times — no sentinel needed. …