4.1.5

Strings

Test yourself

Strings

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

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Concatenation

  • Concatenation is joining two strings together.
  • This can be done with the + sign. E.g:
    • "Hello " + "World" = "Hello World".
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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.
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Length of a string

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

Jump to other topics

1Components of a Computer

1.1Structure & Function of the Processor

1.1.1Von Neumann Architecture

1.1.2Registers

1.1.3Buses

1.1.4Fetch, Decode, Execute Cycle

1.1.5Factors Affecting CPU Performance

1.1.6Pipelining

1.1.7CPU Architecture

1.2Types of Processors

1.2.1CISC & RISC

1.2.2GPUs & Their Uses

1.2.3Multicore & Parallel Systems

1.3Input, Output & Storage

1.3.1Elements of Computer Systems

1.3.2Types of Computer Systems

1.3.3How Magnetic Storage Works

1.3.4Properties of Magnetic Storage

1.3.5Examples of Magnetic Storage

1.3.6How Optical Storage Works

1.3.7Properties of Optical Storage

1.3.8Examples of Optical Storage

1.3.9Types of Optical Disc

1.3.10Random Access Memory

1.3.11Read Only Memory

1.3.12Uses of Flash Memory

1.3.13Properties of Flash Memory

1.3.14What to do When We Run Out of Memory

1.3.15How Virtual Memory Works

2Software & Software Development

2.1Systems Software

2.1.1Operating Systems

2.1.2Managing Memory

2.1.3Paging

2.1.4Segmentation

2.1.5Device Management & Drivers

2.1.6Interrupts

2.1.7Interrupt Service Routine (ISR)

2.1.8Scheduling

2.1.9Types of Scheduling

2.1.10Types of Operating System

2.1.11BIOS

2.1.12Virtual Machines

2.2Applications Generation

2.2.1Applications Software

2.2.2Utilities

2.2.3Encryption Software

2.2.4Defragmentation Software

2.2.5Data Compression Software

2.2.6Backup Software

2.2.7Open Source Software

2.2.8Proprietary Software

2.2.9Licensing Issues

2.2.10Compilers

2.2.11Interpreters

2.2.12Assemblers

2.2.13Compiling a Program

2.2.14Lexical Analysis

2.2.15Compilation Stages

2.2.16Linkers, Loaders & Libraries

2.3Software Development

2.3.1Algorithmic Thinking

2.3.2Waterfall Lifecycle

2.3.3Waterfall Lifecycle - Strengths & Weaknesses

2.3.4Agile Methodology

2.3.5Agile Methodology - Strengths & Weaknesses

2.3.6Extreme Programming

2.3.7Extreme Programming - Strengths & Weaknesses

2.3.8Spiral Methodology

2.3.9Spiral Methodology - Strengths & Weaknesses

2.3.10Rapid Application Development

2.3.11RAD - Strengths & Weaknesse

2.4Types of Programming Language

2.4.1High Level Programming Languages

2.4.2Low Level Programming Languages

2.4.3Programming Paradigms

2.4.4Procedural Programming Languages

2.4.5Assembly

2.4.6Machine Code

2.4.7Modes of Addressing Memory

2.4.8Object-Oriented Languages

2.4.9Classes

2.4.10Objects

2.4.11Encapsulation

2.4.12Polymorphism

3Exchanging Data

3.1Compression, Encryption & Hashing

3.1.1Compression

3.1.2Run Length Encoding

3.1.3Dictionary Coding

3.1.4Encryption

3.1.5Symmetric Encyrption

3.1.6Hashing

3.2Databases

3.2.1Records

3.2.2Databases

3.2.3Relational Databases

3.2.4Entity Relationship Modelling

3.2.5Managing Databases

3.2.6Normalisation

3.2.7SQL

3.2.8Principles of Data Storage

3.2.9Atomicity, Consistency, Isolation & Durability

3.3Networks

3.3.1The Benefits of Networks

3.3.2Network Performance

3.3.3Types of Networks

3.3.4Network Protocols

3.3.5Transmission Protocols

3.3.6What is the Internet?

3.3.7Uniform Resource Locators

3.3.8Domain Name Service

3.3.9Web Hosting

3.3.10Layering Concepts

3.3.11TCP &. OSI Models

3.3.12The Advantages of Layering

3.3.13What's in a Packet?

3.3.14How do Packets get Routed?

3.3.15Did my Data Arrive Safely?

3.3.16Network Hardware

3.3.17Transmission Media

3.3.18Firewalls

3.3.19Proxies

3.3.20Client-Server Model

3.3.21Advantages of the Client Server Model

3.3.22Disadvantages of the Client Server Model

3.3.23Peer-to-Peer Model

3.3.24Advantages of the Peer-to-Peer Model

3.3.25Disadvantages of the Peer-to-Peer Model

3.4Web Technologies

3.4.1HTML

3.4.2CSS

3.4.3JavaScript

3.4.4Search Engine Indexing

3.4.5PageRank Algorithm

3.4.6Server & Client-Side Processing

4Data Types, Data Structures & Algorithms

4.1Data Types

4.1.1Data Types

4.1.2Casting

4.1.3Arrays

4.1.42D Arrays

4.1.5Strings

4.1.6Binary

4.1.7Sign & Magnitude

4.1.8Binary Addition

4.1.9Binary Shifts

4.1.10Hexadecimal

4.1.11Using Hexadecimal

4.1.12Converting Binary & Hexadecimal

4.1.13Converting Denary & Hexadecimal

4.1.14Floating Points in Binary

4.1.15Normalisation of Floating Points

4.1.16Floating Point Addition

4.1.17Floating Point Subtraction

4.1.18Bitwise Manipulation - Shifts

4.1.19Bitwise Manipulation - Masks

4.1.20Character Sets

4.1.21ASCII

4.1.22Unicode

4.2Data Structures

4.2.13D Arrays

4.2.2Linked List

4.2.3Queues

4.2.4Graphs

4.2.5Hash Tables

4.2.6Stacks

4.2.7Trees

4.2.8Binary Search Trees

4.3Boolean Algebra

4.3.1Binary Systems

4.3.2Logic Circuits

4.3.3Boolean Operators

4.3.4Evaluating Expressions

4.3.5Boolean Logic

4.3.6Karnaugh Maps

4.3.7Boolean Identities

4.3.8Boolean Rules

4.3.9Flip Flops

4.3.10Adder 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 & Patents Act (1988)

5.1.4Creative Commons Licensing

5.1.5Regulation of Investigatory Powers Act (2000)

5.2Moral & Ethical Issues

5.2.1Online Activity Tracking

5.2.2Censorship

5.2.3Positive Cultural Impacts

5.2.4Negative Cultural Impacts

5.2.5E-Waste

5.2.6Energy Consumption

5.2.7Positive Environmental Impact

5.2.8Layout, Colour Paradigms & Character Sets

5.2.9Computers in the Workplace

5.2.10Automated Decision-Making

5.2.11Artificial Intelligence

5.2.12Monitoring Behaviour

5.2.13Analysing Personal Information

5.2.14Piracy & Offensive Communication

6Elements of Computational Thinking

6.1Thinking Abstractly

6.1.1Abstraction

6.2Thinking Ahead

6.2.1Inputs & Outputs

6.3Thinking Procedurally

6.3.1Decomposition

6.4Thinking Logically

6.4.1Pseudocode

6.4.2Flow Diagrams

6.5Thinking Concurrently

6.5.1Concurrent Processing

7Problem Solving & Programming

7.1Programming Techniques

7.1.1Variables & Constants

7.1.2Comments

7.1.3Inputs & Outputs

7.1.4Subroutines

7.1.5Scope

7.2Programming Construction

7.2.1Integrated Development Environments

7.2.2The Purpose of Testing

7.2.3Types of Testing

7.2.4Test Plans

8Algorithms

8.1Algorithms

8.1.1Interpreting Algorithms

8.1.2Correcting Algorithms

8.1.3Completing Algorithms

8.1.4Sort Algorithms

8.1.5Bubble Sort

8.1.6Insertion Sort

8.1.7Merge Sort

8.1.8Search Algorithms

8.1.9Linear Search

8.1.10Binary Search

8.1.11Quick Sort Algorithm

8.1.12A* Algorithm

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2D Arrays

Binary