REPEAT: key INPUT ("Press X to exit") UNTIL key =="X" This code uses: Selection Sequencing Iteration

Answer 1

The code snippet you've provided is a simple loop structure that demonstrates iteration. Let's break down the concepts you mentioned:

1. Selection: This refers to making choices in code based on conditions (like if-else statements). In your snippet, there isn't an explicit selection structure, but the use of key == "X" can be thought of as a condition being evaluated.

2. Sequencing: This involves executing statements in a specific order. Your code follows this principle as it clearly defines the order of operations - prompting for a key press, checking the key pressed, and continuing the loop until the condition (i.e., key being "X") is met.

3. Iteration: This is the repeated execution of a block of code. Your use of REPEAT...UNTIL is a prime example of iteration, as it repeats the instructions until the specified condition is satisfied.

To summarize, while your code shows clear examples of iteration and sequencing, selection is less evident in the structure provided. If you were to add an if-statement to handle different key presses, it would explicitly illustrate the selection concept as well. Here’s how you might expand the snippet to include selection:

REPEAT 
    key = INPUT("Press X to exit or any other key to continue") 
    IF key != "X" THEN 
        PRINT("You pressed: " + key) 
    END IF 
UNTIL key == "X"

This expanded version includes a selection structure (IF statement) while still demonstrating sequencing and iteration.