1.2.25

ASCII & Unicode

Test yourself on ASCII & Unicode

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American Standard Code for Information Interchange

The American Standard Code for Information Interchange (ASCII) character set is the most common character set.

7-bit

7-bit

  • Initially, each character in ASCII was represented by a seven-bit binary code.
  • That means there was a maximum of 128 characters.
    • This was enough to include all commonly used letters and symbols in the English language.
  • When each letter is represented by seven bits, an 8-bit system can use the extra bit as a check digit.
8-bit

8-bit

  • An extended ASCII uses all 8 bits.
  • The additional bit allows for an extra 128 characters to be represented.
  • With that extension, most Western languages can use the same character set.
  • Note: In your exam, the representation of ASCII will use 8 bits.

Unicode

Unicode is a character set which was released because of the need to standardise character sets internationally.

Unicode

Unicode

  • Unicode aims to represent every possible character in the world.
  • The most common form of Unicode is UTF-8 and uses between eight and 32 bit binary codes to represent each character.
Compatability

Compatability

  • The first 256 characters in Unicode are identical to extended ASCII, which makes it backwards compatible with documents encoded using older character sets.
  • Characters may not be recognised or displayed correctly if the computer it is being read on is using a different character set from the computer it was created on.
Types of characters

Types of characters

  • Unicode represents characters from all major alphabets of the world.
  • Unicode is also used to represent emojis!

Logical Ordering

Both ASCII and Unicode store characters in a logical, numerical order.

ASCII - example

ASCII - example

  • Denary
    • 'A' = 65
    • 'B' = 66
    • 'a' = 97
    • 'b' = 98
  • Hex
    • 'A' = 41
    • 'B' = 42
    • 'a' = 61
    • 'b' = 62
Unicode - examples

Unicode - examples

  • 'A' = U+0391
  • 'B' = U+0392
  • 'a' = U+0061
  • 'b' = U+0062
Notes

Notes

  • The codes for uppercase letters are different from the codes for lowercase letters.
  • The character for 'B' will be one more than the character code for 'A', and so on.
Jump to other topics
1

Computer Systems

1.1

Systems Architecture

1.1.1Fetch-Execute Cycle1.1.2Common CPU Components & Their Function1.1.3Von Neumann Architecture1.1.4Factors Affecting CPU Performance1.1.5Embedded Systems1.1.6Exam-Style Questions - Von Neumann Architecture1.1.7Diagnostic Misconceptions - Embedded vs General
1.2

Memory & Storage

1.2.1Types of Memory1.2.2Flash Memory1.2.3Properties of Flash Memory1.2.4Running Out of Memory1.2.5Virtual Memory1.2.6Units of Capacity1.2.7Calculating Capacity Requirements1.2.8Solid State Storage1.2.9Properties of Solid State Media1.2.10Magnetic Storage1.2.11Properties of Magnetic Media1.2.12Examples of Magnetic Storage1.2.13Optical Storage1.2.14Properties of Optical Media1.2.15Examples of Optical Storage1.2.16Types of Optical Disk1.2.17Number Bases1.2.18Converting Number Bases1.2.19Hexadecimal1.2.20Using Hexadecimal1.2.21Converting Denary & Hexadecimal1.2.22Binary Addition1.2.23Binary Shifts1.2.24Representing Text1.2.25ASCII & Unicode1.2.26Representing Images1.2.27Converting Binary & Images1.2.28Representing Sound1.2.29Data Compression1.2.30Grade 9 - Storage1.2.31Exam-Style Questions - Primary Memory1.2.32Exam-Style Questions - Storage1.2.33Exam-Style Questions - Data Conversions1.2.34Diagnostic Misconceptions - RAM vs ROM1.2.35Diagnostic Misconceptions - Bits, Nibbles & Bytes1.2.36Diagnostic Misconceptions - Bits Required to Store1.2.37End of Topic Test - Computer Systems1.2.38End of Topic Test - Representation
1.3

Computer Networks, Connections & Protocols

1.3.1Benefit of Networks1.3.2Types of Networks1.3.3Network Performance1.3.4Networks: How Do Packets Get Routed?1.3.5Client-Server Model1.3.6Pros & Cons of Client-Server Model1.3.7Peer-to-Peer Model1.3.8Pros & Cons of Peer-to-Peer Model1.3.9Network Hardware1.3.10Transmission Media1.3.11What is the Internet?1.3.12URLs1.3.13DNS & Web Hosting1.3.14The Cloud1.3.15Pros & Cons of the Cloud1.3.16Star & Mesh Network Topologies1.3.17WiFi1.3.18WiFi Frequency & Channels1.3.19WiFi Encryption1.3.20IP Addresses1.3.21MAC Addresses1.3.22Network Protocols1.3.23Transmission Protocols1.3.24Application Protocols1.3.25Layers1.3.26Advantages of Layering1.3.27Exam-Style Questions - Networking Models1.3.28Exam-Style Questions - Network Protocols1.3.29Diagnostic Misconceptions - LAN vs WAN
1.4

Network Security

1.4.1Forms of Attack1.4.2Penetration Testing1.4.3Malware1.4.4How Malware Spreads1.4.5Social Engineering1.4.6Phishing1.4.7Cracking Passwords1.4.8Denial of Service Attacks1.4.9Data Interception1.4.10Methods of Data Interception1.4.11SQL Injection1.4.12Network Administration1.4.13Network Forensics1.4.14Protecting Against Malware1.4.15Firewalls1.4.16User Access Levels1.4.17Passwords1.4.18Encryption1.4.19End of Topic Test - Networks
1.5

Systems Software

1.5.1System Software1.5.2Utility Software1.5.3Operating Systems1.5.4User Interfaces1.5.5Memory & Process Management1.5.6File Management1.5.7Device Management1.5.8User Management1.5.9Encryption Software1.5.10Defragmentation Software1.5.11Data Compression Software1.5.12Backup Software
1.6

Ethical, Legal, Cultural & Environmental Concern

1.6.1Open Source Software1.6.2Proprietary Software1.6.3Licensing Issues1.6.4Ethical Issues - The Digital Divide1.6.5Ethical Issues - Net Neutrality1.6.6Ethical Issues - Working Conditions1.6.7Ethical Issues - Censorship1.6.8Exam-Style Questions - Ethical Issues1.6.9Data Protection Act 19981.6.10Computer Misuse Act (1990)1.6.11Copyright Designs & Patents Act (1988)1.6.12Creative Commons Licensing1.6.13Freedom of Information Act (2000)1.6.14Cultural Issues1.6.15Environmental Issues1.6.16Online Activity Tracking & The Internet of Things1.6.17Stakeholders1.6.18Other Impacts of Digital Technology on Society1.6.19End of Topic Test - Software & Issues1.6.20Diagnostic Misconceptions - Open Source
2

Computational Thinking, Algorithms & Programming

2.1

Algorithms

2.1.1Computational Thinking - Abstraction2.1.2Computational Thinking - Decomposition2.1.3Algorithmic Thinking2.1.4Pseudocode2.1.5Flowchart Diagrams2.1.6Interpreting Algorithms2.1.7Correcting Algorithms2.1.8Completing Algorithms2.1.9Search Algorithms2.1.10Binary Search2.1.11Linear Search2.1.12Overview of Sort Algorithms2.1.13Bubble Sort2.1.14Merge Sort2.1.15Insertion Sort2.1.16Exam-Style Questions - Sorting Algorithms
2.2

Programming Fundamentals

2.2.1Variable Declaration & Assignment2.2.2Input & Output2.2.3Program Flow - Sequence2.2.4Program Flow - Selection2.2.5Program Flow - Iteration2.2.6Arithmetic Operators2.2.7Relational Operators2.2.8Boolean Operators2.2.9Data Types2.2.10Casting2.2.11Arrays2.2.12Strings2.2.13File Handling2.2.14Structuring Data - Records2.2.15Structured Query Language2.2.16Random Number Generation2.2.17End of Topic Test - Programming2.2.18Exam-Style Questions - Translation2.2.19Diagnostic Misconceptions - Comparison Operators2.2.20Diagnostic Misconceptions - = & ==2.2.21Diagnostic Misconceptions - Types of Data2.2.22Diagnostic Misconceptions - Last Line of Code2.2.23Diagnostic Misconceptions - Array Index
2.3

Producing Robust Programs

2.3.1Defensive Design2.3.2Validation & Sanitisation2.3.3Authentication & Contingencies2.3.4Maintainability2.3.5Purpose of Testing2.3.6Types of Testing2.3.7Test Plans2.3.8Types of Errors2.3.9End of Topic Test - Programming2.3.10Exam-Style Questions - Testing
2.4

Boolean Logic

2.4.1Binary Systems2.4.2Logic Circuits2.4.3Boolean Logic2.4.4Boolean Operators2.4.5Grade 9 - Logic
2.5

Programming Languages & IDEs

2.5.1High-Level vs Low-Level Languages2.5.2Translation - Compliers & Interpreter2.5.3Translation - Assemblers2.5.4Integrated Development Environments2.5.5Exam-Style Questions - Translation

Practice questions on ASCII & Unicode

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

  1. 1
    Why are the first 256 characters in Unicode identical to extended ASCII?Multiple choice
  2. 2
    What characters are supported by Unicode?Multiple choice
  3. 3
    Which of these can be represented using Unicode?True / false
  4. 4
    Why does Unicode use more bits per character than ASCII?Multiple choice
  5. 5
    Characters in conventional computers are stored in what number system?Multiple choice
Answer all questions on ASCII & Unicode

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Representing Text

Representing Images