Understanding Computer Science (WJEC)
This unit teaches you fundamental principles and concepts related to computer science. These include topics such as such as hardware, logical operations, communication, data representation, operating systems, programming principles, software engineering, and more.
There are many hardware components that you need to learn about during this class. Here are the important ones and their functions:
Central Processing Unit (CPU)
The main part of the PC that runs it
Can process hundreds of millions of instructions each second
Stores data in binary (0s and 1s)
CPU components
Controller: Manages instruction execution
Arithmetic and Logic Unit (ALU): Performs calculations and data comparisons
Registers: Fast, temporary storage (e.g., Accumulator, Program Counter)
Internal Memory: Level 1 cache for fast data access
Buses: Buses allow data to be transferred to different parts of the computer
Address Bus: Transfers storage addresses
Data Bus: Moves data between components
Control Bus: Sends control signals
Cores
Cores are multi-core processors that compute multiple instructions
different devices mean different number of cores
the more the power instructions they can compute simultaneously
Input and Output Devices
Input Devices - devices that take in information from the user
Examples: Mouse, keyboard, microphone, digital camera, scanners, touch screens
Output Devices - devices that relay out info to the user
Examples: Monitor, speakers, printer, projector
Storage
Primary Storage: Refers to memory directly accessible by the CPU, like RAM, used for temporary data storage during processing.
Secondary Storage: Includes devices like hard drives, used for long-term data storage and retrieval.
Data Capacity
Data capacity refers to the amount of data that can be stored, transmitted, or processed by a computer system.
Units: Bit, byte, kilobyte (kB), megabyte (MB), gigabyte (GB), terabyte (TB)
Additional Hardware Components
Motherboard: Main circuit board with CPU, RAM, and other components
Graphics Processing Unit (GPU): Handles graphic calculations, can be integrated or dedicated
Sound Cards: Enable audio output and input, converting analog to digital and vice versa
Embedded Systems
a combination of software and hardware that performs a specific task
Logical operations in computer science are fundamental operations that manipulate boolean values.
Propositional Logic
Boolean algebra evaluates statements to true or false
Propositional logic manipulates statements to simplify or derive logical statements
In computer science, truth tables are used to represent the outputs of logical expressions for all possible input combinations, aiding in understanding and designing logic circuits or algorithms.
Logical Operaions also include a lot of laws that you need to know that make solving easier. Similar to laws in math
Identity Law: A+0=AA + 0 = AA+0=A
Associative Laws: Order of operation doesn't matter with same type operators
Commutative Laws: Order of operands doesn't matter
Distributive Law: X.(Y+Z)=X.Y+X.ZX . (Y + Z) = X . Y + X . ZX.(Y+Z)=X.Y+X.Z
Annulment Law: A+1=1A + 1 = 1A+1=1
Idempotent Law: A+A=AA + A = AA+A=A
Inverse Law: A+Aˉ=1A + Ā = 1A+Aˉ=1
Annulment Law (AND): A.0=0A . 0 = 0A.0=0
Identity Law (AND): A.1=AA . 1 = AA.1=A
Idempotent Law (AND): A.A=AA . A = AA.A=A
Complement Law: A.Aˉ=0A . Ā = 0A.Aˉ=0
Double Complement Law: AˉAˉ=AĀĀ = AAˉAˉ=A
Absorptive Law: A+(A.B)=AA + (A . B) = AA+(A.B)=A
Absorptive Law: A.(A+B)=AA . (A + B) = AA.(A+B)=A
Networks: A network connects multiple computer systems together
Pros of Networks in Computer Science:
Communication between devices and users
Resource sharing (files, printers, internet)
Collaboration among users in different locations
Scalability to accommodate more devices
Centralized management of resources and security
Cost-effective for organizations
Flexibility in accessing resources
Cons of Networks in Computer Science:
Security risks (breaches, cyber attacks)
Complexity in setup and maintenance
Downtime leading to disruptions
Bandwidth limitations affecting performance
Dependency on network for operations
Privacy concerns with data transmission
Compatibility challenges among devices and protocols
Types of networks include Local Area Network and Wide Area Network
only difference is how far the computer systems are within the network and their reach to other systems.
Connectivity
Network Interface Card (NIC): Connects a computer to a network
Connection Methods: Wired (copper, fiber-optic) or wireless (Wi-Fi)
Typical Speeds:
Wired: 100 Mbps to 10 Gbps
Wireless: 54–108 Mbps, affected by distance and conditions
Packets: contain data for a computer system
can share data between the network and to other computer systems
IP Addresses:
unique id assigned to every device,
people have this too in their respective countries.
Assigned by DHCP server or manually
types of IP addresses
IPv4: 32-bit address, e.g., 192.168.1.1
IPv6: 128-bit address, e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334
Protocols
Ethernet Protocol: defines rules for data transmission network (LAN)
Wifi Protocol: checks wifi security for user safety and data safety
Email protocol: various protocols that save data in servers and transfer it to computer systems to keep data safe and encrypted
The Nature of Data
Data: Raw facts and figures (e.g., text, numbers, pictures, sounds, videos).
Information: Data that has been processed to be meaningful.
Counting Systems
Image Representation
an image is made of pixels, the more in pixel in the image, the better the resolution is
Each pixel is a binary number representing color.
Black and white use 1 (black) and 0 (white).
Color images use more bits for RGB values.
Character Representation
Stored as binary numbers.
Character sets map characters to binary numbers.
ASCII is a character encoding standard used in computers and communication equipment to represent text and control characters
Data Types
Integer: Whole numbers (e.g., 42, -11).
Real: Decimal numbers (e.g., 12.9, -17.5).
Boolean: True or False (e.g., 1, 0).
Character: Single symbol (e.g., 'A', '7').
String: Sequence of characters (e.g., "Hello").
Operating systems in computer science involve managing a computer system and the resources within a system.
Management
RAM Management: Prevents programs and data from corrupting each other.
Process Management: Ensures efficient CPU usage without interference between processes.
Security Management: Manages user accounts and passwords.
Providing User Interface
Copying, deleting, moving, sorting, and searching files or folders.
Accessing system settings.
Providing command line and graphical user interfaces (GUIs).
Allowing multiple windows open at once.
Customizing the interface (e.g., desktop background).
Switching between tasks
HCI VS GUI
Human-Computer Interaction (HCI) focuses on users interacting with computers, emphasizing usability and user experience.
Graphical User Interface (GUI) uses graphical icons for user-friendly interaction, contrasting with command-line interfaces.
HCI studies user behaviors to design easy-to-use interfaces.
GUIs visually represent functions for navigation ease.
Both HCI and GUI enhance user experience and system efficiency.
Operating systems
Disk Organization.
File transfer: moving files into different locations
formatting: prepares a disk like a USB or sd card for use with a different device or system
compression: reduces file sizes
High-Level Languages
Programming languages are similar to human languages.
Easier to understand and learn.
Commands are powerful and perform complex tasks.
Python, Java, JavaScript, C++, Ruby, and PHP
Low-Level Languages
Requires knowledge of the CPU's internal structure.
Uses mnemonics, converted to machine code with an assembler.
Specific to a type of CPU and not portable.
Very efficient, resulting in faster programs.
Example: C, Assembly, and Fortran.
Machine Code
Opposite of high-level languages.
Made of bit patterns (instructions or data).
Directly executed by the CPU.
High-level languages need conversion to machine code for execution.
Integrated Development Environments (IDEs) are ways to program for users and run code.
Most popular is VS Code
Provide tools for creating computer programs.
Common IDE Tools
Editor: Enter, format, and edit source code.
Compiler: Converts source code into machine code for later execution.
Interpreter: Converts and executes source code line by line.
Linker: Connects compiled code from libraries.
Loader: Loads compiled code into memory for execution.
Debugger: Identifies and fixes errors in programs.
Trace: Displays executed lines and variable values during runtime.
Break Point: Pauses program at a specific line for debugging.
Variable Watch: Shows current variable values and can interrupt program.
Memory Inspector: Displays memory contents.
Error Diagnostics: Shows error messages for debugging.
Libraries: Contains commonly used functions and subprograms.
Program construction refers to the process of designing, coding, testing, and debugging a computer program to ensure it meets the specified requirements and functions correctly.
Assemblers
Converts assembly language into machine code.
Example:
Assembly Code: AND A
Assembler Conversion: Opcode: 0010, Operand: 0001
Interpreters
Converts high-level programming code into machine code one line at a time
Executes instantly
Analyses
Lexical Analysis removes comments and spaces, replaces keywords with tokens, and creates a symbol table.
Syntax Analysis checks token spelling and grammar, producing error messages for syntax errors.
Semantic Analysis validates variable declarations, data types, and legal operations.
Translators
Changes a program from one language to another language
Translating PASCAL code into C code.
Types of Errors in Coding
Syntax Errors: Occur when commands don't follow expected syntax.
Runtime/Execution Errors: Happen during program execution.
Logical Errors: Cause incorrect output without crashing.
Linking Errors: Occur when correct library isn't linked.
Rounding Errors: Approximating numbers to nearest value.
Truncation Errors: Approximating numbers closer to zero.
This unit teaches you fundamental principles and concepts related to computer science. These include topics such as such as hardware, logical operations, communication, data representation, operating systems, programming principles, software engineering, and more.
There are many hardware components that you need to learn about during this class. Here are the important ones and their functions:
Central Processing Unit (CPU)
The main part of the PC that runs it
Can process hundreds of millions of instructions each second
Stores data in binary (0s and 1s)
CPU components
Controller: Manages instruction execution
Arithmetic and Logic Unit (ALU): Performs calculations and data comparisons
Registers: Fast, temporary storage (e.g., Accumulator, Program Counter)
Internal Memory: Level 1 cache for fast data access
Buses: Buses allow data to be transferred to different parts of the computer
Address Bus: Transfers storage addresses
Data Bus: Moves data between components
Control Bus: Sends control signals
Cores
Cores are multi-core processors that compute multiple instructions
different devices mean different number of cores
the more the power instructions they can compute simultaneously
Input and Output Devices
Input Devices - devices that take in information from the user
Examples: Mouse, keyboard, microphone, digital camera, scanners, touch screens
Output Devices - devices that relay out info to the user
Examples: Monitor, speakers, printer, projector
Storage
Primary Storage: Refers to memory directly accessible by the CPU, like RAM, used for temporary data storage during processing.
Secondary Storage: Includes devices like hard drives, used for long-term data storage and retrieval.
Data Capacity
Data capacity refers to the amount of data that can be stored, transmitted, or processed by a computer system.
Units: Bit, byte, kilobyte (kB), megabyte (MB), gigabyte (GB), terabyte (TB)
Additional Hardware Components
Motherboard: Main circuit board with CPU, RAM, and other components
Graphics Processing Unit (GPU): Handles graphic calculations, can be integrated or dedicated
Sound Cards: Enable audio output and input, converting analog to digital and vice versa
Embedded Systems
a combination of software and hardware that performs a specific task
Logical operations in computer science are fundamental operations that manipulate boolean values.
Propositional Logic
Boolean algebra evaluates statements to true or false
Propositional logic manipulates statements to simplify or derive logical statements
In computer science, truth tables are used to represent the outputs of logical expressions for all possible input combinations, aiding in understanding and designing logic circuits or algorithms.
Logical Operaions also include a lot of laws that you need to know that make solving easier. Similar to laws in math
Identity Law: A+0=AA + 0 = AA+0=A
Associative Laws: Order of operation doesn't matter with same type operators
Commutative Laws: Order of operands doesn't matter
Distributive Law: X.(Y+Z)=X.Y+X.ZX . (Y + Z) = X . Y + X . ZX.(Y+Z)=X.Y+X.Z
Annulment Law: A+1=1A + 1 = 1A+1=1
Idempotent Law: A+A=AA + A = AA+A=A
Inverse Law: A+Aˉ=1A + Ā = 1A+Aˉ=1
Annulment Law (AND): A.0=0A . 0 = 0A.0=0
Identity Law (AND): A.1=AA . 1 = AA.1=A
Idempotent Law (AND): A.A=AA . A = AA.A=A
Complement Law: A.Aˉ=0A . Ā = 0A.Aˉ=0
Double Complement Law: AˉAˉ=AĀĀ = AAˉAˉ=A
Absorptive Law: A+(A.B)=AA + (A . B) = AA+(A.B)=A
Absorptive Law: A.(A+B)=AA . (A + B) = AA.(A+B)=A
Networks: A network connects multiple computer systems together
Pros of Networks in Computer Science:
Communication between devices and users
Resource sharing (files, printers, internet)
Collaboration among users in different locations
Scalability to accommodate more devices
Centralized management of resources and security
Cost-effective for organizations
Flexibility in accessing resources
Cons of Networks in Computer Science:
Security risks (breaches, cyber attacks)
Complexity in setup and maintenance
Downtime leading to disruptions
Bandwidth limitations affecting performance
Dependency on network for operations
Privacy concerns with data transmission
Compatibility challenges among devices and protocols
Types of networks include Local Area Network and Wide Area Network
only difference is how far the computer systems are within the network and their reach to other systems.
Connectivity
Network Interface Card (NIC): Connects a computer to a network
Connection Methods: Wired (copper, fiber-optic) or wireless (Wi-Fi)
Typical Speeds:
Wired: 100 Mbps to 10 Gbps
Wireless: 54–108 Mbps, affected by distance and conditions
Packets: contain data for a computer system
can share data between the network and to other computer systems
IP Addresses:
unique id assigned to every device,
people have this too in their respective countries.
Assigned by DHCP server or manually
types of IP addresses
IPv4: 32-bit address, e.g., 192.168.1.1
IPv6: 128-bit address, e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334
Protocols
Ethernet Protocol: defines rules for data transmission network (LAN)
Wifi Protocol: checks wifi security for user safety and data safety
Email protocol: various protocols that save data in servers and transfer it to computer systems to keep data safe and encrypted
The Nature of Data
Data: Raw facts and figures (e.g., text, numbers, pictures, sounds, videos).
Information: Data that has been processed to be meaningful.
Counting Systems
Image Representation
an image is made of pixels, the more in pixel in the image, the better the resolution is
Each pixel is a binary number representing color.
Black and white use 1 (black) and 0 (white).
Color images use more bits for RGB values.
Character Representation
Stored as binary numbers.
Character sets map characters to binary numbers.
ASCII is a character encoding standard used in computers and communication equipment to represent text and control characters
Data Types
Integer: Whole numbers (e.g., 42, -11).
Real: Decimal numbers (e.g., 12.9, -17.5).
Boolean: True or False (e.g., 1, 0).
Character: Single symbol (e.g., 'A', '7').
String: Sequence of characters (e.g., "Hello").
Operating systems in computer science involve managing a computer system and the resources within a system.
Management
RAM Management: Prevents programs and data from corrupting each other.
Process Management: Ensures efficient CPU usage without interference between processes.
Security Management: Manages user accounts and passwords.
Providing User Interface
Copying, deleting, moving, sorting, and searching files or folders.
Accessing system settings.
Providing command line and graphical user interfaces (GUIs).
Allowing multiple windows open at once.
Customizing the interface (e.g., desktop background).
Switching between tasks
HCI VS GUI
Human-Computer Interaction (HCI) focuses on users interacting with computers, emphasizing usability and user experience.
Graphical User Interface (GUI) uses graphical icons for user-friendly interaction, contrasting with command-line interfaces.
HCI studies user behaviors to design easy-to-use interfaces.
GUIs visually represent functions for navigation ease.
Both HCI and GUI enhance user experience and system efficiency.
Operating systems
Disk Organization.
File transfer: moving files into different locations
formatting: prepares a disk like a USB or sd card for use with a different device or system
compression: reduces file sizes
High-Level Languages
Programming languages are similar to human languages.
Easier to understand and learn.
Commands are powerful and perform complex tasks.
Python, Java, JavaScript, C++, Ruby, and PHP
Low-Level Languages
Requires knowledge of the CPU's internal structure.
Uses mnemonics, converted to machine code with an assembler.
Specific to a type of CPU and not portable.
Very efficient, resulting in faster programs.
Example: C, Assembly, and Fortran.
Machine Code
Opposite of high-level languages.
Made of bit patterns (instructions or data).
Directly executed by the CPU.
High-level languages need conversion to machine code for execution.
Integrated Development Environments (IDEs) are ways to program for users and run code.
Most popular is VS Code
Provide tools for creating computer programs.
Common IDE Tools
Editor: Enter, format, and edit source code.
Compiler: Converts source code into machine code for later execution.
Interpreter: Converts and executes source code line by line.
Linker: Connects compiled code from libraries.
Loader: Loads compiled code into memory for execution.
Debugger: Identifies and fixes errors in programs.
Trace: Displays executed lines and variable values during runtime.
Break Point: Pauses program at a specific line for debugging.
Variable Watch: Shows current variable values and can interrupt program.
Memory Inspector: Displays memory contents.
Error Diagnostics: Shows error messages for debugging.
Libraries: Contains commonly used functions and subprograms.
Program construction refers to the process of designing, coding, testing, and debugging a computer program to ensure it meets the specified requirements and functions correctly.
Assemblers
Converts assembly language into machine code.
Example:
Assembly Code: AND A
Assembler Conversion: Opcode: 0010, Operand: 0001
Interpreters
Converts high-level programming code into machine code one line at a time
Executes instantly
Analyses
Lexical Analysis removes comments and spaces, replaces keywords with tokens, and creates a symbol table.
Syntax Analysis checks token spelling and grammar, producing error messages for syntax errors.
Semantic Analysis validates variable declarations, data types, and legal operations.
Translators
Changes a program from one language to another language
Translating PASCAL code into C code.
Types of Errors in Coding
Syntax Errors: Occur when commands don't follow expected syntax.
Runtime/Execution Errors: Happen during program execution.
Logical Errors: Cause incorrect output without crashing.
Linking Errors: Occur when correct library isn't linked.
Rounding Errors: Approximating numbers to nearest value.
Truncation Errors: Approximating numbers closer to zero.
