Explain how different input and output devices can be applied as a solution to different problems.
Describe the characteristics and uses of RAM and ROM.
Understand what is meant by virtual storage.
Learn the main characteristics, operational principles and purpose of: Hard disk drives (HDD), Optical disks, Solid-State Disks (SSD)
Explain the need for Secondary Storage, compare characteristics and make suitable recommendations.
Lesson Notes
Hardware?
Any physical component of a computer system.
Core Components
Hardware needed to run the core computer. Can be referred to as internal hardware components. List of these components below:
Motherboard
Central Processing Unit (CPU)
Random Access Memory (RAM)
Graphics Card (GPU)
Solid State Drive (SSD) and Hard Disk Drive (HDD)
Fan
Power Supply Unit (PSU)
Network Interface Card (NIC)
Peripheral Device
Addition hardware connected externally. Can be referred to as external hardware components. Peripheral devices can be categorised as:
Input Device - Hardware used to put data into a system.
Output Device - Hardware used to present data to a user.
Input Devices
Input devices are essential hardware components that allow users to interact with computers by providing data and control signals to the computer. Here are five common examples of input devices:
Keyboard - The classic text input device with keys for letters, numbers, symbols, and special functions.
Mouse - A pointing device used to control the cursor and interact with elements on a screen. Typically has two buttons and a scroll wheel.
Scanner - Similar to a mouse, but built into laptops and trackpads. Senses finger movement on its surface for control.
Touch Pad - Converts physical documents, photos, or images into digital format for storage or editing on a computer.
Microphone - Captures audio input for voice recognition, online communication, or audio recording.
Touchscreen - A display that detects the presence and location of touch, common in smartphones, tablets, and interactive kiosks.
Graphics Pad - A camera built into or connected to a computer for video conferencing, recording, or streaming.
Motion Sensor - Used for playing games and controlling simulations, often with buttons and directional controls.
Webcam - Detects motion and converts this into a signal the initiates and action in a system.
Game Controller - A pressure-sensitive surface that translates hand movements with a digital pen into digital input for drawing, painting, or image editing.
Output Devices
Output devices play a crucial role in presenting information from a computer to the user. They take data processed by the computer and translate it into various forms, such as audio, visual, or printed output. Here are five common examples of output devices:
Monitor - Displays text, images, and videos on a screen for visual output.
Printer - Generates physical copies of digital documents, images, and text.
Speaker - Produces sound from computers, playing music, videos, games, and notifications.
Headphones - Provides personal audio experience, isolating sound and protecting others.
Projector - Enlarges and projects computer screen onto a larger surface for presentations or entertainment.
Television - Displays video content from computers, streaming services, or other sources.
Interactive Projector - Combines projector functionality with touch input for interactive presentations or learning experiences.
Smart Display - Offers a combined interface with touchscreen and voice control, displaying information and enabling interaction.
Virtual Reality Headset - Creates an immersive, 3D visual and audio experience for games, simulations, or entertainment.
Haptic Feedback Devices - Provides physical feedback like vibrations or forces to enhance user experience in applications like gaming or simulations.
Storage Devices
Refers to any hardware component that stores data long term. Data on storage devices are not lost when the power is turned off.
The 3 main types of storage are:
Magnetic - Hard Disk Drives
Solid State - Solid State Drives, USB Flash Drives
Optical - CDs, DVDs, Blu-Ray
Magnetic Storage
A magnetic disk drive consists of a number of platters (disks) coated in a magnetic material. The data is encoded into bits and written onto the surface as a series of changes in the direction of the magnetisation. Data is stored in small areas on the disk called sectors. A "metal arm" is used to read and write to the disk.
HDD Advantages
Cheaper than Solid State
Higher capacity than Solid State
Longer read/write cycle than Solid State
Examples:
How does it work?
HDDs are made up of many disks (platters) coated in a magnetic material.
The magnetic material holds data as each particle/grain can be orientated to be north or south facing, representing 1 or 0.
The actuator arm (metal arm) moves up and down the disks, and can read and write to them by changing the polarity of the magnetic coating.
The surface of each disk is organised into concentric tracks, which are then also split into sectors, which are individually addressed by the operating system.
Solid State Storage
Solid-state storage (SSS) refers to a type of non-volatile computer storage that stores and retrieves digital information using only electronic circuits, without any involvement of moving mechanical parts.
Most solid-state storage devices use NAND flash memory, which is electrically programmable and non-volatile.
SSD Advantages
Faster than HDDs
Does not need to be defragmented
Shockproof
Makes basically no noise
Low power consumption
Examples:
How does it work?
Each cell works by delivering a current along the bit and the word lines to activate the flow of electrons from the source towards the drain.
The current on the word line is strong enough to force a few electrons across an insulated oxide layer into a floating gate.
Once the current is turned off, these electrons are trapped and stored.
Another transistor called a control gate transistor is then used to read and write data to the floating gate transistor.
A thin layer of oxide is placed between the two transistors, effectively trapping the charge inside the floating gate.
The state of the NAND cell is determined by measuring the charge in the floating gate. No charge is considered a 1 and some charge is considered a 0.
Comparing Magnetic (HDD) and Solid State (SSD) Storage
Price: SSDs are about 10 times more expensive than HDDs per MB
Power: HDDs uses about 3 times more battery power than SSDs
Capacity: SSDs are generally no larger than 512 GB but HDDs go up to 4 TB
Speed: SSDs are almost twice as fast at loading up and copying files
Noise: SSDs are silent whereas HDDs make spinning disc sounds
Reliability: Both are highly reliable forms of storage but the magnetic disc is more vulnerable to knocks as it has moving parts
Optical Storage
Storage on disks. Data is read using a laser. Data is stored on small indentations (data pits) on the shiny surface of the disk.
Advantages:
Cheap
Portable
Disadvantages:
Low storage capacity
Easily damaged
Examples:
Optical disks are available as:
Read only (CD-ROM) (Can only be read from)
Recordable (CD-R) (Can be written too once)
Re-writable formats (CD-RW) (Can be written too many times)
Each format uses different techniques to identify pits and lands.
Recordable (writeable) formats use a transparent dye that becomes opaque when heated by a laser.
Re-writable formats use a laser to change the state of a phase-change alloy and a magnet to set the new state.
How does it work?
An optical disk consists of a single layer of material, on which is a spiral track, which the information is encoded onto.
In the tracks of read-only disks, there are pits and lands, covered in a protective layer, representing 1s and 0s, which are read by a laser, and interpreted as data.
Writeable optical disks use a photosensitive dye, which can become translucent or opaque depending, which is what represents the 1s and 0s.
Separate lasers for writing and reading change the transparency of the dye, and interpret the data respectively.
The term 'optical disk' covers many types, such as CD, DVD, or Blu-Ray.
Exam Question:
Why are the capacities of CDs, DVDs and Blu-Ray discs different, given they are all the same physical size?
Different laser wavelengths 'burn' smaller pits.
The spiral track can therefore be more tightly wound, creating a longer track.
Comparison of Storage Devices
Hard Disk (HDD)
Solid State Disk (SDD)
Optical Disk (CD/DVD)
Optical Disk (Blu-ray)
Typical Capacity
High (1TB)
Medium (500GB)
Low (900MB to 4.7GB)
Low (25GB - 50GB)
Relative Cost
Medium
High
Low
Low
Easily Portable
External disks are available
External disks are available
Yes
Yes
Relative Power Consumption
High
Low
High
High
Relative speed of access
Medium
High
Low
Low
Latency
High
Low
Very High
High
Fragmentation
High
None
Reliability
Good
Very Good
Fair
Fair
Relative Physical Size
Large
Small
Large
Large
Where can they be used?
HDD - Cheap and plentiful storage for desktop PCs, or for backing up large amounts of data.
Optical disk - Storing films or music (although recently becoming much less common)
SSD - Flash drives used for portable storage, SSDs used in mobile devices/laptops, and as a faster replacement in desktop PCs.
Cloud Storage
The "Cloud" refers to software applications and data are held on a remote server on the Internet. It is typically accessed using a Web browser such as Chrome or Edge.
Examples:
Google Drive
One Drive
Dropbox
iCloud
Advantages of Cloud Storage:
Access files from any connected device.
Files can be shared easily.
Easy to increase storage.
Backing up data is no longer crucial, it is done by the service provider.
Service provider also provides security.
Can store data for free - Limit.
Does not require expensive hardware.
Disadvantages of Cloud Storage:
Need an Internet connection.
Upload/download speed depends on bandwidth.
Dependent on host for security and back-ups.
Data can be vulnerable to hackers.
Unclear who owns the cloud data.
Subscription fees may be expensive - Long term.
Factors that affect the choice of storage
Cost
Storage Size
Physical Size
Performance
Reliability
Random Access Memory - RAM
RAM is volatile, meaning that the information stored in it is erased when you restart or shut down your computer.
It temporarily holds the files you are currently working on.
When you switch between programs or pages, the data stored in RAM is instantly available.
Slower than cache, faster than secondary storage.
Read Only Memory - ROM
ROM is non-volatile, which means the information is permanently stored on the chip. Turning off the computer does not impact ROM.
ROM stores instructions that do not change, such as the initial boot-up portion of the software or firmware instructions for devices like printers.
Memory Management
Cache
Cache is very fast RAM that is close to the CPU. Data that needs to be processed by the CPU is stored in the cache. The larger the cache size, the more data can be stored closer to the CPU.
Virtual Memory/Storage
Virtual storage refers to the concept of extending a computer's memory beyond its physical limits by utilizing secondary storage (such as a hard disk) as additional primary memory.
Virtual memory is temporary storage created on the Hard Disk when the RAM is full. Frees up space on the RAM to load new applications.
Memory Hierarchy
The higher you go up the memory hierarchy you go the faster the data transfers become. However the capacity of the memory components gets smaller.
