Computer Science (9-1) - 0984 CIE

Arrays

Overview

Imagine storing the marks of 100 students in 100 separate variables, then trying to add them up. It would be unbearable. An array solves this by holding many values of the same type under a single name, each reachable by a number called its index, so a short loop can sweep through them all.

In this lesson you will learn to declare and use one-dimensional and two-dimensional arrays in the Cambridge pseudocode style, understand why arrays are so useful, and write values into and read values from an array using iteration, with full worked routines you can adapt in the exam.

Objectives

1 Declare and use one-dimensional (1D) and two-dimensional (2D) arrays
2 Understand the use of arrays
3 Write values into, and read values from, an array using iteration

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Flashcards

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Lesson Note

Almost every real program handles lists of data: scores, names, prices, pixels. Arrays are the basic structure for storing such lists, and the programming paper expects you to declare them, put data in, take data out, and process them with loops. Master the array-and-loop pattern and a whole class of problems becomes routine.

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Lesson Evaluation

Congratulations on completing the lesson on Arrays. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.

You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.

Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.

What must be true of all the items stored in one array? A. they must be integers B. they must be the same data type C. they must be strings D. they must be unique Answer: B
What is used to identify the position of an element in an array? A. its value B. its data type C. its index D. its identifier Answer: C
Which declaration creates a 1D array of 8 integers indexed 1 to 8? A. DECLARE A : INTEGER B. DECLARE A : ARRAY[1:8] OF INTEGER C. DECLARE A : ARRAY OF 8 D. DECLARE A[8] Answer: B
Which loop structure is normally used to process every element of a 2D array? A. a single WHILE loop B. a REPEAT loop C. a nested (loop inside a loop) D. no loop is needed Answer: C
Before adding all elements of an array into a variable Total, Total should first be: A. set to the first element B. set to 0 C. left undeclared D. set to the array length Answer: B

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