Chapter: Basic Machine Organisation
Hello everyone! Welcome to your study notes for Basic Machine Organisation. Ever wondered what's really going on inside your computer or smartphone when you play a game, watch a video, or do your homework? This chapter pulls back the curtain!
We'll explore the main parts of a computer, how they work together, and how the computer's "brain" processes information. Think of it like learning the anatomy of a computer. Understanding these basics is super important because it's the foundation for everything else in ICT. Don't worry if it sounds tricky at first, we'll use simple examples and analogies to make it easy to understand. Let's get started!
1. The Main Hardware Parts of a Computer System
A computer system is made up of different hardware components that work together. We can group them into five main functions. A great way to remember this is to think about how your own body works!
Input Devices: How you give the computer information. (Like your senses: eyes, ears, touch)
Processing Units: The 'brain' that thinks and calculates. (Like your brain)
Output Devices: How the computer gives information back to you. (Like your voice or actions)
Storage Devices: Where the computer keeps information for the long term. (Like your long-term memory)
Bus System: The pathways that connect everything together. (Like your nervous system)
All these parts work together to take in data (input), think about it (process), and show you the results (output), while using memory (storage) to keep track of things.
Key Takeaway
A computer's hardware has five main jobs: Input, Processing, Output, Storage, and using the Bus System to communicate between parts.
2. The Brain of the Computer: Processing Units
The processing units are where all the action happens. They are the most important part of the computer system. There are two main types you need to know.
Central Processing Unit (CPU)
The CPU is the main brain of the computer. It performs most of the calculations and executes the instructions for computer programs.
Analogy: Think of the CPU as a master chef in a kitchen. It reads the recipe (the program instructions) and prepares the ingredients (the data) to create the final meal (the output).
A CPU has two main components:
Control Unit (CU): The 'manager' of the CPU. It directs and coordinates all the operations. It fetches instructions from memory and tells the other parts what to do. It doesn't execute instructions itself, it just manages the process.
Arithmetic Logic Unit (ALU): The 'calculator' of the CPU. It performs all the mathematical calculations (like addition, subtraction) and logical operations (like comparing if one number is bigger than another).
Graphics Processing Unit (GPU)
The GPU is a specialised processor designed to handle complex graphics and image-related tasks. It's extremely good at doing the same calculation over and over again on a huge amount of data, which is perfect for rendering images, videos, and games.
Analogy: If the CPU is the master chef who can cook anything, the GPU is a specialist pastry chef who is incredibly fast and efficient at making beautiful, complex desserts (graphics).
Measuring CPU Performance
The main way we measure a CPU's speed is its clock speed, measured in Hertz (Hz). Clock speed tells you how many instruction cycles the CPU can handle per second.
Example: A 3 GHz (Gigahertz) CPU can perform 3 billion cycles per second!
These cycles are incredibly fast. We use tiny units of time to describe them:
Microsecond (µs): One millionth of a second.
Nanosecond (ns): One billionth of a second.
Picosecond (ps): One trillionth of a second.
Quick Review
CPU: The main brain for general tasks. Contains the Control Unit (manager) and ALU (calculator).
GPU: A special brain for graphics.
Clock Speed: Measures how many cycles a CPU can run per second (measured in Hz).
3. The CPU's Daily Routine: The Machine Cycle
So how does the CPU actually process instructions? It follows a constant, repeating cycle for every single instruction. This is called the fetch-decode-execute cycle or the machine cycle.
Analogy: Think about making a sandwich following a recipe book.
Fetch: The CPU's Control Unit fetches (gets) the next instruction from the main memory (RAM). (Your brain tells your hand to get the next step from the recipe book).
Decode: The Control Unit decodes the instruction, figuring out what action needs to be taken. (You read the instruction and understand it means "put cheese on bread").
Execute: The ALU performs the mathematical or logical operation. (You physically place the cheese on the bread).
This cycle repeats itself billions of times every second! To do this, the CPU needs help from two other key components:
Registers: These are tiny, extremely fast storage locations located directly inside the CPU. They are used to temporarily hold data and instructions that the CPU is working on right now. Think of them as the chef's hands, holding the ingredients they are about to use.
Buses: These are the communication pathways or 'highways' that connect the CPU to other components like the main memory (RAM) and input/output devices. Data and instructions travel along these buses during the machine cycle.
Key Takeaway
The CPU continuously runs the Fetch-Decode-Execute cycle. It fetches instructions from memory, decodes them to understand what to do, and executes them. Registers are the CPU's super-fast internal storage, and Buses are the highways that connect everything.
4. The Computer's Workbench: Main Memory
Main memory is the computer's short-term working area. It holds the data and programs that the CPU is currently using. It's much faster than long-term storage, but it usually holds less information.
Random Access Memory (RAM)
Function: This is the main workbench. When you open a program like a web browser or a game, it gets loaded from your storage drive into RAM so the CPU can access it quickly.
Characteristics: RAM is volatile, which means it forgets everything when the power is turned off. It is also "random access" because the CPU can access any part of it directly and instantly.
Performance: More RAM generally means you can run more programs at the same time smoothly. The speed of RAM (its data access rate) also affects performance.
Read-Only Memory (ROM)
Function: ROM contains essential startup instructions for the computer, often called the BIOS or UEFI. This tells the computer how to check its hardware and load the operating system when you first turn it on.
Characteristics: ROM is non-volatile, meaning it keeps its information even when the power is off. As the name suggests, its contents are read-only and cannot be easily changed.
Memory Cache
Function: Cache is a very small, extremely fast type of memory that sits between the CPU and the main RAM. It stores copies of the data and instructions that the CPU uses most frequently.
Analogy: If RAM is the workbench, cache is a tiny pocket on the chef's apron. The chef keeps their most-used spice (frequent data) in their pocket so they don't have to reach over to the workbench every time.
Memory Concepts and Performance
Memory Size: The amount of data memory can hold (e.g., 16 GB of RAM). Larger size allows for more multitasking.
Memory Address: Each location in memory has a unique address, like a house number on a street. This allows the CPU to find data and instructions precisely.
Word Length: This refers to the number of bits (e.g., 32-bit or 64-bit) that a CPU can process at one time. A larger word length means the computer can handle more data in each cycle, leading to better performance.
Did you know? Memory Units
In computing, prefixes like kilo, mega, and giga are based on powers of 2, not 10!
Common Mistake Alert: Don't mix up the computer system (binary) with the international system (SI/decimal).
1 Kilobyte (KB) = 1024 Bytes
1 Megabyte (MB) = 1024 KB
1 Gigabyte (GB) = 1024 MB
1 Terabyte (TB) = 1024 GB
Quick Review: Memory Comparison
Cache: Fastest, smallest, inside/next to CPU.
RAM: Fast, medium-sized, volatile (forgets when power is off).
ROM: Slower, small, non-volatile (remembers when power is off).
5. Talking to the Computer: Input and Output Devices
These devices are how we humans interact with the computer. Input devices send data IN, and output devices get data OUT.
Common Input Devices
Keyboard: Used to type text and commands. Advantages: Fast for text. Disadvantages: Bulky.
Mouse/Touchpad: Used to control a pointer on the screen. Advantages: Intuitive for graphical interfaces. Disadvantages: Needs a flat surface.
Microphone: Used to record sound. Application: Voice chat, recording music.
Scanner: Used to create a digital copy of a physical document or image. Application: Digitising old photos.
Webcam: Used to capture video. Application: Video conferencing.
Common Output Devices
Monitor/Screen: Displays visual information (text, images, video). Application: The primary way to see what the computer is doing.
Printer: Creates a physical copy (hard copy) of digital documents. Advantages: Permanent record. Disadvantages: Requires ink/toner and paper.
Speakers/Headphones: Produces sound. Application: Listening to music, watching movies.
Projector: Displays computer output onto a large screen or wall. Application: Presentations in a classroom.
For your exams, you should be able to select and justify the use of an appropriate device. For example, to give a presentation to a large class, you should choose a projector because its output can be seen by many people at once, which is not possible with a small monitor.
6. The Computer's Library: Storage Devices
Storage is the computer's long-term memory. It's where you save your files, games, and operating system. Unlike RAM, storage is non-volatile, so it keeps your data safe even when the computer is turned off.
Memory vs. Storage: A common confusion! Memory (RAM) is the temporary workbench for things you are actively using. Storage (SSD/HDD) is the permanent library for everything you own.
Key Characteristics of Storage
Access Method: Can be random access (can jump to any piece of data directly, like a hard disk or SSD) or sequential access (must read through the data from the beginning to get to a specific point, like an old magnetic tape).
Volatility: Almost all storage is non-volatile.
Storage Capacity: How much data it can hold (e.g., 1 TB).
Data Transfer Rate: How fast data can be read from or written to the device.
Examples of Storage Devices
Magnetic Disk (Hard Disk Drive - HDD): Uses spinning magnetic platters to store data. Characteristics: High capacity, cheap, but slower and more fragile than SSDs. Random access.
Flash Memory (Solid State Drive - SSD, USB drive): Uses electronic chips with no moving parts. Characteristics: Very fast, durable, but more expensive than HDDs. Random access.
Optical Disk (CD, DVD, Blu-ray): Uses lasers to read tiny pits on a spinning disc. Characteristics: Cheap, good for software/movie distribution, but has lower capacity and is becoming less common. Random access.
Magnetic Tape: A long strip of magnetic tape used for data storage. Characteristics: Huge capacity, very cheap, but very slow because it uses sequential access. Used mainly for large-scale backups and archives.
Network Storage: Storing data on servers over a network or the internet (e.g., cloud storage like Google Drive). Advantages: Accessible from anywhere. Disadvantages: Requires an internet connection.
Trend: Over time, storage devices are becoming faster, with greater storage capacity, and a smaller physical size.
7. What's New? Latest Developments
Technology is always improving! You just need to be aware of the general trends (you don't need the super technical details).
Processor Capabilities: CPUs now have multiple "cores" (e.g., quad-core), which are like having multiple CPUs in one chip, allowing them to do more tasks at once. They are also becoming more power-efficient.
Primary Memory Technologies: RAM technology gets faster with each new generation (e.g., DDR4, DDR5), allowing the CPU to get data more quickly. Capacities are also increasing.
Secondary Storage Devices: SSDs are becoming the standard in most new computers because their speed provides a huge performance boost. New, even faster connections (like NVMe) are making them quicker still.
Data Communications: The buses and connections inside the computer (like PCIe) are getting faster, allowing components like the GPU and SSD to communicate with the CPU more quickly.
And that's it for Basic Machine Organisation! You now know the fundamental building blocks of a computer and how they all work together. Keep reviewing these concepts, and you'll have a solid foundation for the rest of your ICT studies. Well done!