Hardware and network technologies

Hardware

Hardware is the physical components or workings of a computer system. It includes input, processing and output devices. The Central Processing Unit (CPU) can be thought of as the brain of the computer. The performance of the CPU is affected by the number of cores, clock speed and memory.

The CPU and memory work together to process instructions and run programs. There are different types of memory – volatile and non-volatile.

Purpose of the CPU

The purpose of the CPU is to process data and carry out instructions. Whatever you are using your computer for, be it playing computer games or surfing the web, the CPU is working in the background. Data and instructions are transported around the CPU through the use of buses.

The CPU is the most important part of a computer, responsible for all the processing that is carried out. It processes data using the fetch-execute cycle.

Components of the CPU

The CPU is made up of several components. The structure of these components is referred to as the ‘computer architecture’. Most computers today use a Von Neumann architecture – Control Unit (CU), Arithmetic and Logic Unit (ALU) and Immediate Access Store (IAS).

The CPU contains:

1. The Control Unit (CU)
   • Coordinates the timing of the different components and the flow of data in the CPU
   • Is responsible for fetching and decoding instructions and managing their execution on the processor
   • Controls and monitors the hardware attached to the computer
   • Tells the ALU, the computer’s memory and the hardware devices how to respond to an instruction
   • Communicates with the rest of the components by using the control bus
2. The Arithmetic and Logic Unit (ALU) is where the CPU performs the arithmetic and logic operations. Data is passed to the ALU to allow the required calculations to be carried out. The results of any calculations are then sent to be stored in a register. There are two parts to the ALU:
   • The arithmetic part, which deals with calculations, e.g. 1 + 2 = 3
   • The logic part, which deals with any logical comparisons, such as the comparison of two numbers, e.g. 2 > 1
   Typically, the ALU includes a register that it uses to store intermediate results of calculations. This register is known as the accumulator.
3. The Immediate Access Store (IAS)
   • This is where the CPU holds all the data and programs it is currently using
   • The IAS is often referred to as the registers, which are a very small amount of storage. In a 64-bit processor, each register will store just 64 bits

Fetch-execute cycle

The fetch-execute cycle is the steps a CPU goes through in order to process an instruction.

At the start of the fetch-execute cycle, both the data and the instruction are loaded into the computer’s main memory so they are ready to be processed.

What is an instruction?

An instruction is an action that a program wants the CPU to carry out. For example, this could be to move specific data from one memory location (register) to another. The table below shows three instructions. Each instruction is made up of an operator and two operands.

The CPU first fetches an instruction from the RAM. It then decodes this instruction to work out what operation it needs to do (the operator), and what the operands are (the data). Finally, the CPU will execute the instruction.

Instruction	Operator	Operand	Execution
move, #161, r0	move	#161	Place value 161 into register 0
move, #16, r1	move	#16	Place value 16 into register 1
add, r0, r1	add	–	Add the values in registers 0 and 1

In this example, the CPU places 161 into register 0, places 16 into register 1 and adds both numbers together. This would require three cycles of fetch-execute.

Fetching an instruction

The Program Counter (PC) copies the address of the next instruction it contains into the Memory Address Register (MAR).

The MAR places the address to be used on to the address bus.

The instruction on the data bus is loaded into the Memory Data Register (MDR).

The MDR copies the instruction into the Instruction Register (IR).

Executing an instruction

The instruction in the IR is carried out (executed) by the CPU. This will generally involve the ALU carrying out a calculation.

Now that the CPU is executing an instruction, the Program Counter can now be reset to point to the next instruction.

Summary of the fetch-execute cycle

1. The processor checks the program counter to see which instruction to run next
2. The Program Counter gives an address value in the memory of where the next instruction is
3. The processor fetches the instruction value from this memory location
4. Once the instruction has been fetched, it needs to be decoded and executed. For example, this could involve taking one value, putting it into the ALU, then taking a different value from a register and adding the two together
5. Once this is complete, the processor goes back to the Program Counter to find the next instruction
6. This cycle is repeated until the program ends

CPU performance

Not all processors are equal. Some perform better, and are therefore usually more expensive, than others.

Factors affecting the performance of the CPU:

• Clock speed:Clock speed indicates how fast a CPU can run. It is measured in hertz, which deals with how many cycles (instructions) the CPU can process in one second. A 3 gigahertz (gHz) CPU performs 3 billion cycles a second.
• Number of cores: A CPU can contain one or more cores. It is common for computers to have multiple cores, such as dual core or quad core processors. The more cores a processor has, the more able it is to run multiple programs at the same time.
• Cache:Cache memory is a type of very fast memory situated on or very close to the CPU. It is used to temporarily hold instructions and data the CPU is likely to reuse.

Input and output devices

An input device is one that is used to get data into a computer. An output device is one that allows data to leave a computer, most often in a form intelligible to a human user. Some devices, such as touch screens, are hybrid devices and can do both.

Examples of input devices:

Input device	Advantages	Disadvantages	Characteristics / Typical uses
Microphone	Readily available (in smart phones, tablets, PCs etc.).	Sometimes picks up background noise.	Converts analogue sound waves into digital format. Voice recording on a phone. Talking to friends online.
Mouse	Allows a user to control a computer using a GUI.	Requires a certain level of dexterity to use. Can be inaccurate when interpreting precise movements (e.g. drawing).	Selecting icons and options from menus on a screen.
Graphics digitiser	Can create more accurate digital hand drawings than a mouse.	Relatively expensive. Requires a certain level of expertise to operate.	Graphic designers sketching ideas on a computer.
Touch sensitive screen	Both an input and output device. Very easy to use.	Can become dirty over time. Small objects/icons on screen may be hard to touch accurately. Can be even less accurate than a mouse for precise work.	They work very like a mouse. Used on smart phones, tablets, information kiosks etc.

Examples of output devices:

Output device	Advantages	Disadvantages	Characteristics / Typical uses
Speaker	Allows users to hear music, voices or communications directly from the computer.	Some internal speakers have poor sound quality.	Used to listen to music or video. Visually impaired users rely on speakers to communicate with a computer.
Laser printer	Can print large numbers of pages quickly and in high quality.	More expensive than some other types of printer. Cost to replace toner is relatively high.	Used in schools and offices to print large volumes of data.
3D printer	Allows for rapid production of prototypes and the ability to customise the products you are printing.	Still very expensive and their use is limited by size constraints.	Printing car parts, prosthetics and even human organs.

Storage devices

Secondary storage refers to any device that can store data, in addition to main memory. Secondary storage devices are non-volatile and are typically high capacity, portable or both.

Factors affecting the choice of a secondary storage device include:

• speed (how quickly data can be accessed)
• cost per storage unit (i.e. price per gigabyte or megabyte)
• durability (toughness)
• portability (how easy it is to move it from one computer to another)

Uses, advantages and disadvantages of storage media:

Storage device	Advantages	Disadvantages	Characteristics / Typical uses
Magnetic storage: Hard Disc Drive (HDD)	Relatively cheap per unit of storage. Fast access and retrieval times compared to other storage devices.	Can be easily damaged, will slow down and eventually break over time. Slower access than Solid State Drives.	The main storage device in most computer systems.
Optical storage: Blu-ray disk	Can hold a lot more data than a standard DVD, meaning it can store movies with better picture and sound quality. Portable.	More expensive than DVDs. Requires a Blu-ray player. Can lose data when scratched.	A laser reads from and writes to Blu-ray disks. Used to store HD movies and other HD recordings.
Electrical storage: Solid State Storage Devices (SSD)	Very compact in size and therefore very portable. High speed of data transfer and low power consumption.	Considerably more expensive per unit than magnetic storage. More vulnerable to abrupt power loss and electro-magnetic fields.	USB flash drives and solid state hard drives have replaced the traditional HDD in some new computers. Memory cards are used as a convenient and portable removable storage medium.

Internal memory

Random Access Memory (RAM)

Otherwise known as main memory, this is the component of a computer that stores programs currently being executed, or data needed for immediate use. RAM is volatile, meaning its contents are lost if the computer loses power.

Overview:

• Volatile
• Used to hold programs and data currently in use
• Used to hold the operating system when the computer is switched on

Read Only Memory (ROM)

Some parts of a computer’s memory are marked ‘read only’, which means their contents cannot be changed or deleted. The contents of ROM are safe when a computer loses power (non-volatile).

For these reasons, ROM is ideal for storing instructions that must not be lost or overwritten, such as the BIOS (Basic Input Output System) or the MAC address (in a network card).

Traditionally, the BIOS (the computer boot up instruction set) was always stored in ROM because it is non-volatile. However, flash memory (which is also non-volatile, but not read-only) is now often used for the BIOS so that changes to the instructions can be made.

A ‘bootstrap program’ loads the BIOS as well as any system data that does not change (for example, the hard disk and the amount of RAM installed).

Overview:

• Non-volatile
• Can be read from, but not written to
• ROM is used to hold basic computer hardware settings and, in the past, it held the BIOS to boot up the computer

Cache

RAM is comparatively slow to access when compared to the speed at which registers work. So, to help speed up the processing time, cache memory is used to store instructions or data that are either frequently used, have recently been used or are about to be used. This means they don’t have to be fetched directly from RAM.

Overview:

• Instructions can be read, or written to
• Faster access speeds than RAM
• Small in capacity compared to RAM
• Stores frequently accessed program instructions
• The larger the cache capacity, the faster the CPU performance

Network technologies

When we connect computers together to share data, software and hardware, we create a network. Network protocols (rules) are used to send files over the network as data packets.

Packets contain information in the packets header, which allows them to be sent, received and reassembled in the correct order.

What is a network?

A network is when two or more computing devices are connected together in order to share data, files or hardware.

A network can be just two devices connected to share data; your smart phone connected to your smartwatch or wireless headphones can be considered a network.

A computer that is not connected to a network is called a stand-alone.

Network advantages

• Users can share files and resources (e.g., hardware, software licences and processing power) with others
• Site licences allow software to be installed across an organisation and can be cheaper than buying several individual copies
• Users can access files and resources from another computer on the same network
• Servers can be created to centrally control a number of operations and services on a network, such as security and file backup
• Communications can be sent to any computer on the network
• Peripherals can be shared (printers, scanners and Network Attached Storage (NAS) drives) and potentially save money

Network disadvantages

• Buying network cabling and file servers can be expensive
• Managing a large network can be complicated, requiring training. A network manager may also need to be employed, adding to costs
• Networks can be subject to internal security issues. Human users can often be a weak point – e.g., selecting weak passwords, leaving terminals unlocked and removing or misplacing data via personal storage devices
• There is a danger of external unauthorised access through hacking, particularly with wide area networks. Security procedures are needed to prevent such abuse, e.g. a firewall
• Malware and viruses can be introduced from either internal or external sources and can spread from computer to computer. It may be difficult to control and eradicate this issue
• Depending on the structure of the network, if an element of it fails this could cause the whole network to fail, or cause other issues for the rest of the network
• A high amount of network traffic can cause the whole network to run slowly

LAN and WAN

Networks are often classified according to geographical size or space.

A Local Area Network (LAN) is a network that covers a small geographical area. They are normally contained within a single building or cluster of buildings. Since the distances involved are small, a direct physical connection (for example using cables or wi-fi) is possible.

LANs can be found in homes, schools and small businesses.

A Wide Area Network (WAN) is a network that covers a large geographical area. A WAN could cover a city, a country or even several countries or continents.

These networks make use of a range of communication infrastructure including public telephone lines, undersea cables and communication satellites.

LANs, on the other hand, connect via ethernet cables or wi-fi. The internet is an example of a WAN. A WAN is often a collection of connected LANs.

The web and the internet of things

The internet is a global network of networks. It uses the TCP/IP protocols to allow computers to communicate with each other. The internet is the name for the infrastructure and hardware. It should not be confused with the world wide web.

The world wide web (www) is a collection of files held on web servers that are connected by hypertext. The server then uses HTTP (HyperText Transfer Protocol) to send requested web pages to users.

The internet of things (IoT) connects ‘smart’ devices over the internet and enables them to collect and exchange data.

A good example of the IoT in action is the use of smart meters to control heating in our homes. Connected devices let you turn on heating remotely, adjust the temperature and turn the heating off when there’s no-one home (using motion-sensor cameras or GPS on smartphones to tell if anyone is in the house).

An intranet is a local or private network accessible only to selected individuals (e.g., an organisation’s staff). It is essentially a private network created using world wide web software and protocols.

Communications technologies

Wi-fi is a trademarked name for the IEEE 802.11 standard. It is a medium range wireless technology used to connect devices together. Wi-fi uses radio waves to provide a connection to the internet.

The radio waves are transmitted by a Wi-fi Access Point (WAP) that normally has a wired connection to the internet. Think of how your phone or laptop connects to the internet via the wireless router in your home.

Examples of wi-fi include:

• 2.4 GHz – ultra-high frequency
• 5 GHz – super-high frequency

These numbers refer to two different ‘bands’ your wi-fi can use for its signal. The biggest difference between the two is speed. Under ideal conditions, 2.4 GHz wi-fi will support up to 450 Mbps or 600 Mbps, while 5 GHz wi-fi will support up to 1300 Mbps.

Wi-fi networks are often protected and usually require a network key (essentially a password) in order to log in. Devices that use wi-fi need to have a wireless adapter to enable them to communicate with the wireless router.

A wireless adapter or wireless network card is a hardware device that converts binary data to radio wave signals. A wireless router is a hardware device that receives the radio signals and routes them along a series of similar devices to their destination.

Advantages of wi-fi:

• Allows you to set up LANs without wires
• Wi-fi enabled devices are now widely available
• Users can log in from anywhere within the wi-fi network using any wi-fi device

Disadvantages of wi-fi:

• Signal strength weakens the further away you are from the router
• The wireless connection may not be as secure as a wired connection
• Wi-fi signal can be affected by adverse weather conditions. Water droplets absorb the 2.4 Ghz radio frequency and partially block the signal (however, most WAPs are located indoors)

Bluetooth communicates using radio frequencies and requires no physical cable connections. It was designed to enable a range of portable devices to connect both to each other and to other, less portable, hardware.

Common uses of bluetooth are sharing data files between mobile phones, or sending audio to bluetooth speakers. It operates over a short range (typically between 10-100m). The range can be affected by obstacles (e.g., furniture, walls etc.), but devices do not need to have a direct line of sight to connect.

Advantages of bluetooth:

• Low cost to set up
• Uses relatively little power compared to other types of wireless connection
• You can easily set up bluetooth networks with other bluetooth enabled devices

Disadvantages of bluetooth:

• Short range
• Low level of security
• Low data transmission rate

Fibre optic cable uses light and consists of glass or plastic wires/cores or filaments bundled together and encased in a jacket. Light is transmitted in pulses which represents of a range of frequencies.

The transmitter in the router sends light pulses representing binary code. When the data is received, it is decoded back to its binary form and the computer displays the data. Each core has a mirror-lined wall which reflects light back along the core (total internal reflection) to minimise signal degradation. The cable can vary in length from a few metres to hundreds of kilometres.

Light is passed through the cable using a transmitter. The transmitter in the router sends light pulses representing binary code. When the data is received, it is decoded back to its binary form and the computer displays the message.

Advantages of optical fibre:

• Supports broadband/multiple data transmissions
• Impervious to electromagnetic interference
• Impervious to corrosion
• Minimal signal loss over distance
• Signal difficult to intercept without destroying it

Disadvantages of optical fibre:

• Fibre optic cable is much more expensive to install than traditional copper cable (although it does last a lot longer)
• Optical fibres require more protection around the cable compared to copper

Mobile Communication Technology – 4G and 5G

Mobile broadband is the delivery of an internet service using mobile phone technology. There are several ways of providing mobile broadband including 3G, 4G and 5G.

4G is the fourth generation of mobile phone technology. 2G technology was suitable for making calls and sending text messages while 3G made it possible to access the internet through your mobile phone.

4G services make it much quicker to surf the web on mobiles, tablets and laptops. Because of this, 4G is ideally suited for services which demand more capacity like video streaming, mapping and social networking sites.

There is a big speed increase with 4G – at about 12-15 Mbps, it’s up to five times faster than 3G. This means 4G provides an additional speed boost for video viewing and increasingly important business services such as mobile video conferencing and cloud computing. 4G also allows for cost-effective, stable international calls on internet calling services, such as Skype, Facetime or Messenger, even at peak times.

5G is the fifth generation of mobile network technology. 5G technology promises mobile data speeds that far outstrip the fastest home broadband network currently available in the UK. With speeds of up to 100 gigabits per second, 5G will be as much as 1,000 times faster than existing bandwidth.

Network resources

Network Interface Card (NIC): A circuit board installed in a computer to allow it to be connected to a network. Wireless networks require devices to be fitted with a Wireless Network Interface Card (WNIC).

Network cables:Local Area Networks (LANs) can make use of both cable and wireless media. Wireless gives the convenience of not having cables attached to the computer. However, using cables in a LAN means you can transfer data faster, more reliably and more securely.

There are two types of network cable. Ethernet cables contain copper wires that carry electric signals. Optical cables are made from fibre glass, which carries data around a network via pulses of light.

Router: A device which connects two or more networks together. It is responsible for forwarding packets of data from one network to another and works out the best route for data to travel between computers. A router will scan a packet of data that enters the device to see whether its destination is the network in which it is currently travelling, or another network. It will then forward the packet to its destination.

Switch: A switch performs a very similar function to a router, except it only operates within a single network. It scans a packet of data that enters the device to see what the destination of the package is, then forwards the package to its destination. Switches are often used to join together sections of a LAN.

Network topologies

There are different ways of setting up a Local Area Network (LAN) and each of these have different benefits in terms of network speed and cost. Three network topologies are bus, star and ring.

Bus network

In a bus network all the computers, servers and printers are joined to one cable – ‘the bus’. At each end of the cable a terminator is fitted to stop signals reflecting back down the bus.

Advantages:

• Very easy to install
• Cheap to install – requires very little cabling in comparison to other topologies

Disadvantages:

• If the main cable fails or gets damaged, the whole network will fail
• As more workstations are connected, the performance of the network becomes slower

Ring network

In a ring network, each device (computer, server or printer) is connected in a ring, so each is connected to two others. Each data packet on the network travels in one direction. Each device receives each packet in turn until the packet reaches its destination.

Advantages:

• A ring network can transfer data quickly (even if there are many devices connected) as data only flows in one direction, so there won’t be any data collisions

Disadvantages:

• If the main cable fails or any device is faulty, then the whole network will fail

Star network

In a star network, each device on the network has its own cable that connects to a switch or hub. This is the most popular way of setting up a LAN. You may find a star network in a small network of five or six computers where speed is a priority.

Advantages:

• Very reliable – if one cable or device fails, all the others will continue to work
• Rarely slows down as no data collisions can occur

Disadvantages:

• Expensive to install as this type of network uses the most cable
• Extra hardware is required (hubs or switches). These also add to the cost
• If a hub or switch fails, all the devices connected to it will have no network connection