Arrays & Strings

Arrays

Arrays are really useful when you have access to large amounts of related data, but you don't want to store in multiple variables.

Arrays

An array is a data structure that stores a fixed number of values under a single identifier.
The values must be of the same type.

Array elements

Each piece of data inside an array is called an element.
Each element has an index, which is its position within the array.
We start counting the indices from 0.

Arrays in pseudocode

An array of ten items can be created using the following syntax:
- array name_of_array[10]
Values can be assigned as follows:
- name_of_array[0] = "Hello"
Values can be accessed as follows:
- print(name_of_array[0])

2D Arrays

A 2D array is the data structure which consists of an array of arrays.

2D Array

A 2D array is a data structure where arrays are filled with other arrays.
This can be used to represent a 2D surface, or records.

Accessing elements

To access an individual array, we can access the array as usual:
- array = my2DArray[4]
To access an individual element, we use this syntax:
- array[5][0]
This would get the first element of the sixth array.

Applications of 2D arrays

2D arrays are often used to represent a 2D surface, for example a chess board:
- Each element of the 2D array could contain the chess piece in that location.
2D arrays can be used to represent a database:
- The outer array stores a collection of records.
- The inner arrays store a single record.

Strings

Strings are special cases of arrays or lists, where each element is a character. There are many methods we can apply to them:

Concatenation

Concatenation is joining two strings together.
This can be done with the + sign. E.g:
- "Hello " + "World" = "Hello World".

Accessing a character

Remember, strings are just lists. So we can access a specific character in the exact same way as we access a list element:
- string[3] would get the fourth character.

Length of a string

The length of a string is given by the len function:
- len("Hello") would give 5.

Substrings

A substring is a part of a longer string.
In pseudocode, we use the function:
- stringname.subString(startPos, numberOfChars)
This takes a substring starting at the 'startPos'th character, and takes the stated number of characters.

1Components of a Computer

1.1Structure & Function of the Processor

1.1.1Structure of the CPU

1.1.2Fetch, Decode, Execute Cycle

1.1.3Factors Affecting CPU Performance

1.1.4CPU Architecture

1.2Types of Processors

1.2.1CISC & RISC

1.2.2Multicore & Parallel Cores

1.3Input, Output & Storage

1.3.1Computer Systems

1.3.2Magnetic Storage

1.3.3Optical Storage

1.3.4Types of Optical Storage

1.3.5Types of Memory

1.3.6Flash Memory

1.3.7Virtual Memory

2Software & Software Development

3Exchanging Data

4Data Types, Data Structures & Algorithms

4.1Data Types

4.1.1Data Types

4.1.2Arrays & Strings

4.1.3Representing Numbers

4.1.4Binary Arithmetic

4.1.5Hexadecimal

4.1.6Converting Binary Numbers

4.1.7Floating Points in Binary

4.1.8Floating Point Arithmetic

4.1.9Bitwise Manipulation

4.1.10Character Sets

4.2Data Structures

4.2.1Arrays, Linked Lists & Queues

4.2.2Graphs, Hash Tables & Stacks

4.2.3Trees

4.3Boolean Algebra

4.3.1Computational Logic

4.3.2Boolean Logic

4.3.3Karnaugh Maps

4.3.4Boolean Identities

4.3.5Flip Flops & Adder Circuits

5Legal, Moral, Cultural & Ethical Issues

5.1Computing Related Legislation

5.1.1Data Protection Act (1998)

5.1.2Computer Misuse Act (1990)

5.1.3Copyright Designs and Patents Act (1988)

5.1.4Regulation of Investigatory Powers Act (2000)

5.2Moral & Ethical Issues

5.2.1Online Activity Tracking

5.2.2Censorship

5.2.3Cultural Issues

5.2.4Environmental Issues

5.2.5Layout, Colour Paradigms & Character Sets

6Elements of Computational Thinking

6.1Thinking Abstractly

6.1.1Abstraction

6.2Thinking Procedurally

6.2.1Decomposition

6.3Thinking Logically

6.3.1Pseudocode & Flow Diagrams

7Problem Solving & Programming

7.1Programming Techniques

7.1.1Programming Fundamentals

7.1.2Modularity

7.2Programming Construction

7.2.1Integrated Development Environments

7.2.2Testing

8Algorithms

8.1Algorithms

8.1.1Interpreting, Correcting & Completing Algorithm

8.1.2Sort Algorithms

8.1.3Insertion & Merge Sort

8.1.4Search Algorithms

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