Difficulty: Beginner | Prerequisites: Computer Basics Overview (Part 1)
Once you know that a computer is made of hardware and software, the next step is understanding what the hardware actually consists of. This topic breaks hardware into four categories: input devices (how you tell the computer what to do), output devices (how it shows you results), storage devices (where data lives permanently) and memory/processor (where data is held and processed in the moment). You need to know Part 1's definitions of hardware and software before this makes sense. This material feeds directly into understanding how a computer's performance is determined.
Computer hardware splits into input devices (keyboard, mouse, scanner), output devices (monitor, printer, speakers), storage devices (hard disk, floppy disk, CD-ROM, DVD) and memory (RAM for temporary working data, ROM for permanent read-only instructions). The CPU is the processor that performs all calculations, and its speed, together with RAM size and hard disk performance, determines how fast the computer runs.
Input device
Any hardware component used to send data or commands to the computer. Examples: keyboard, mouse, scanner, joystick, touch pad, light pen.
In simple terms, how you tell the computer what to do.
Output device
Any hardware component the computer uses to communicate results back to the user. Examples: monitor (VDU), printer, plotter, speakers, speech synthesiser.
In simple terms, how the computer shows you what it is doing.
Storage device
Hardware that holds data permanently (or until deliberately erased). Examples: hard disk drive, floppy disk, CD-ROM, DVD.
Think of it as the computer's filing cabinet.
RAM (Random Access Memory)
The main working memory of the computer. Volatile, meaning its contents are lost when the computer is switched off. The operating system and running programs are loaded into RAM from disk.
Think of it as the computer's desk: whatever it is working on right now sits here, but it is cleared when you leave.
ROM (Read Only Memory)
A special memory chip holding software that can be read but not written to. The ROM-BIOS chip is a common example. ROM retains its contents when power is off.
Think of it as a permanently printed instruction manual built into the machine.
CPU (Central Processing Unit)
The microprocessor that performs all calculations within the computer. Often called "the brain of the computer." Its speed is measured in MHz (or GHz). A higher MHz value means faster processing.
In simple terms, the chip that does all the thinking.
Bit
The smallest unit of data in computing: a single 1 or 0 in the binary numbering system.
Byte
A group of eight bits. Roughly enough to store one character (a letter or digit).
Kilobyte (KB)
1,024 bytes.
Megabyte (MB)
1,024 kilobytes (approximately one million bytes).
Gigabyte (GB)
1,024 megabytes (approximately one billion bytes).
Keyboard – the most common way to enter information into a computer
Mouse – used to navigate graphical interfaces (e.g. Microsoft Windows)
Tracker ball – an alternative to the mouse, often favoured by graphic designers for precision
Scanner – converts printed material into a digital file format the PC can use
Touch pad – a pressure-sensitive surface, commonly found on laptops
Light pen – allows users to point directly at areas on the screen
Joystick – used mainly for games
VDU (Visual Display Unit) / Monitor – the screen, used to display information in a readable format
Printer – produces a physical (hard copy) version of digital information
Laser printers are common in large organisations because of speed and quality
Inkjet printers are typical for home use
Plotter – similar to a printer but designed for larger images (e.g. architectural drawings)
Speakers – produce audio output, used in education and presentations
Speech synthesiser – converts text on screen into spoken words
Hard disk drive (HDD)
Internal, high-capacity storage
Also holds the operating system
Speed measured by "average access time" in milliseconds (lower = faster)
Capacity typically in the gigabytes range
Cheapest cost per unit of storage
Floppy disk (diskette) – 1.44 MB capacity, very slow, very cheap, portable but largely obsolete
CD-ROM – around 650 MB capacity, slower than hard disks, read-only in standard form
Speed rated as multiples of the original 1x specification
DVD – up to 17 GB capacity, faster than CD-ROM but slower than hard disks, slightly more expensive than CD-ROMs
RAM (Random Access Memory)
The computer's main working memory
The operating system loads into RAM when you switch on
Programs and data are loaded into RAM from storage when needed
Volatile: contents are lost when the computer is powered off
More RAM generally means better performance
ROM (Read Only Memory)
Holds permanent software that can be read but not overwritten
The ROM-BIOS chip is the classic example (contains startup instructions)
Network cards and video cards also often contain ROM chips
Non-volatile: retains contents without power
1 bit = a single binary digit (0 or 1)
1 byte = 8 bits
1 kilobyte (KB) = 1,024 bytes
1 megabyte (MB) = 1,024 KB
1 gigabyte (GB) = 1,024 MB
The Central Processing Unit performs all calculations
Speed measured in MHz (megahertz); higher = faster
A 600 MHz processor is significantly faster than a 400 MHz processor
PCs primarily use Intel-architecture microprocessors (historically 386, 486, Pentium line)
Three main factors determine how fast a computer runs:
CPU speed
RAM size
Hard disk speed and capacity
Understanding input/output devices helps you choose the right tool for a task: a scanner for digitising paper documents, a plotter for large-format engineering drawings. Knowing about storage trade-offs (speed, capacity, cost) is how IT teams decide backup strategies and how much disk space to provision for a department.
Students often confuse RAM with hard disk storage. RAM is temporary (volatile) working memory. Hard disk storage is permanent. When you save a file, it moves from RAM to the hard disk.
"ROM" does not mean "storage." ROM is a chip soldered to the motherboard containing permanent startup instructions. It is not where you save your essays.
Students sometimes assume a higher-capacity hard disk means a faster computer. Capacity (how much it holds) and speed (how quickly it reads/writes) are separate specifications.
A byte is not one bit. A byte is eight bits. This trips people up in unit-conversion questions.
⚠️ Be able to classify any given device as input, output or storage.
⚠️ Know the difference between RAM and ROM (volatile vs non-volatile, read-write vs read-only).
⚠️ Memorise the memory measurement chain: bit → byte → KB → MB → GB, each step multiplied by 8 (bit to byte) or 1,024.
⚠️ Know the three factors that affect computer performance: CPU speed, RAM size, hard disk speed/capacity.
True or false: A keyboard is an output device. (False, it is an input device.)
Fill in the blank: 1 byte = ______ bits. (8)
True or false: ROM loses its contents when the computer is switched off. (False, ROM is non-volatile.)
Fill in the blank: The three factors affecting computer performance are CPU speed, ______ size and hard disk speed/capacity. (RAM)
True or false: A CD-ROM typically holds around 650 MB. (True)
Q: Name three input devices and explain what each does.
A: Keyboard (enters text and commands), mouse (navigates graphical interfaces and selects items), scanner (converts printed material into a digital file).
Q: What is the difference between RAM and ROM?
A: RAM is the main working memory, volatile (lost on power-off), and used to hold running programs and data. ROM is a read-only chip, non-volatile (retained on power-off), holding permanent instructions such as the BIOS.
Q: Convert 2 gigabytes into megabytes.
A: 2 GB = 2 x 1,024 = 2,048 MB.
Q: Why does adding more RAM generally improve a computer's performance?
A: More RAM allows the computer to hold more programs and data in fast working memory simultaneously, reducing the need to swap data to and from the much slower hard disk.
Q: Compare CD-ROM and DVD drives in terms of capacity and speed.
A: CD-ROM holds around 650 MB; DVD holds up to 17 GB. DVD drives are faster than CD-ROM drives but still slower than hard disks.
This material builds on the Computer Basics Overview (Part 1), which introduced hardware as a concept. It connects forward to the Software, Networks and Security notes (Part 3), where the operating system and application software run on top of the hardware covered here. Understanding storage devices also lays the groundwork for the backup and virus-prevention sections in Part 3.
input devices, output devices, storage devices, RAM, ROM, CPU, microprocessor, hard disk, floppy disk, CD-ROM, DVD, bit, byte, kilobyte, megabyte, gigabyte, VDU, monitor, printer, plotter, scanner, keyboard, mouse, tracker ball, touch pad, light pen, joystick, speakers, speech synthesiser, computer memory, volatile memory, non-volatile memory, average access time, MHz, computer performance factors