Arrays

This lesson introduces arrays. Arrays are data structures that can store and collect a number of items with the same data type. These arrays are used to store a collection of data, and can also be used to reference the data throughout the program. You can also pick specific points of data from these arrays to use. Items can be added to and subtracted from preexisting arrays. This can remove the use of multiple variables, which can make the program easier to read and less complicated. There are multiple types of arrays as well. Fixed arrays are arrays with a size that has been set when it was created. Dynamic arrays are arrays that are designed to have data points be removed or added. These arrays don't have a fixed size. ^[1]

Objectives and Skills

Objectives and skills for this lesson include:

• Understand single and multi-dimensional arrays
• Understand dynamic arrays
• Understand associative arrays
• Use arrays to implement program functionality

Readings

1. Rebus: Programming Fundamentals
2. Wikipedia: Array data type
3. Wikipedia: Dynamic array
4. Wikipedia: Associative array

Multimedia

1. YouTube: Programming For Beginners - Arrays
2. YouTube: Programming For Beginners - Dictionaries and Hashes
3. YouTube: Static Arrays vs. Dynamic Arrays
4. YouTube: An Overview of Arrays and Memory (Data Structures and Algorithms #2)
5. YouTube: What is an Array? - Processing Tutorial
6. YouTube: Multidimensional Arrays

Practice

• Defined-Value Arrays
• Fixed-Length Arrays
• Dynamic Arrays

Examples

Activities

Complete the following activities using pseudocode, a flowcharting tool, or your selected programming language. Use separate functions for input, each type of processing, and output. Avoid global variables by passing parameters and returning results. Create test data to validate the accuracy of each program. Add comments at the top of the program and include references to any resources used.

Lesson Summary

• Depending on the language, array types may overlap (or be identified with) other data types that describe aggregates of values, such as lists and strings. Array types are often implemented by array data structures, but sometimes by other means, such as hash tables, linked lists, or search trees.^[3] In Python, the built-in array data structure is a list.^[4]
• Each element in an array will be assigned an index position. Most programming languages will begin at index position 0. This allows the program to recall data stored in a specific position. for instance, an array named "months" would have the data value "March" stored at index position 2. A program can reference this value by referring to "months[2]".^[5]
• Arrays can have multiple axes (more than one axis). Each axis is a dimension. Thus a single-dimension array is also known as a list. A two-dimension array is commonly known as a table.^[6]
• Arrays are an important complex data type used in almost all programming. We continue to concentrate on simple one dimension arrays also called a list. Most programmers develop a series of user-defined specific task functions that can be used with an array for normal processing. These functions are usually passed the array along with the number of elements within the array. Some functions also pass another piece of data needed for that particular functions task.^[7]
• Finding a specific member of an array means searching the array until the member is found. It’s possible that the member does not exist and the programmer must handle that possibility within the logic of his or her algorithm.^[8]
• It is important to follow the "Don't Repeat Yourself" (DRY) principle. Rather than having to keep repeating yourself, you can use loops to visit each element of an array and the loop control variable as an array index. This allows for more efficient code and smaller programs.^[9]

Key Terms

array

Data structure consisting of a collection of elements (variables or values), each identified by at least one index or key.^[10] It can also be defined as an ordered collection of items indexed by contiguous inters.^[11]

array member

An item or value in an array.^[12]

dimension

An axis of an array. Defines the amount of associated pieces of data that can be stored.^[13]

don’t repeat yourself

A principle of software development aimed at reducing repetition of software patterns, replacing it with abstractions, or repetition of the same data, using data normalization to avoid redundancy.^[14]

dynamic array

A random access, variable-size list data structure that allows elements to be added or removed. The size can be changed when new items are added.^[15]

flexible coding

Using the size of an array to determine the number of loop iterations required.^[16]

index notation

Used to specify the elements of an array. Most current programming languages use square brackets [] as the array index operator.^[17] There are different methods for referring to the elements of a list, a vector, or a matrix, depending on whether one is writing a formal mathematical paper for publication, or when one is writing a computer program. ^[18]

linear search

Sequentially checks each element of the list for the target value until a match is found or until all the elements have been searched.^[19]

list

Lists are a form of compiled data, in which there are two types, linear lists which are similar to static arrays, and linked lists, which are similar to dynamic arrays. They can compile multiple different data types.^[20]

offset

The method of referencing array members by starting at zero.^[21]

parallel array

A form of implicit data structure that uses multiple arrays to represent a singular array of records.^[22] Also known as structure an array (SoA), multiple arrays of the same size such that i-th element of each array is closely related and all i-th elements together represent an object or entity.^[23]

sort

Arranging data according to their values.^[24]

static array

An array with its length not changing. Items can be replaced or changed but no more can be added or subtracted.^[25]

table

A two dimensional array.^[26] A data structure used to organize information, just as it is on paper. There are many different types of computer-related tables, which work in a number of different ways. The following are examples of the more common types.^[27]

Assessments

• Quizlet: Flash Cards
• Quizlet: Aditional Flash Cards
• Quizlet: Quiz

See Also

• TutorialsPoint: Arrays in Computer Programming

References