Computer Systems

What is a computer system?

A computer system is a collection of hardware and software that works together to achieve some data processing task

What is hardware?

Hardware is the physical components of a computer system

What is software?

Software is any set of instructions that tells the hardware what to do

What is the purpose of a computer?

The purpose of a computer is to:

1. Take data

2. Process it

3. Output it.

What is an input device?

An input device is a device used to insert data into a computer system

What is an example of an input device?

Examples of an input device: ★ Keyboard ★ Mouse ★ Microphone

What is the purpose of a keyboard?

A keyboard is used to input text

What is a processing device?

A processing device is any hardware component that can analyze and interpret input.

What is an example of a processing device?

Examples of a processing device: ★ CPU ★ GPU

What is an output device?

An output device is a device that can show the result of processed data

What is an example of an output device?

Examples of an output device: ★ Speakers ★ Printer ★ Monitor

What does a speaker do?

A speaker outputs sounds

What is a storage device?

A storage device is a piece of computer equipment on which information can be stored.

What is an example of a storage device?

Examples of a storage device: ★ RAM ★ ROM ★ Hard drive

What does RAM do?

RAM stores data, application and operating system whilst in use.

What is system software?

★ Exam-board definition: System software manages the computer system resources and acts as a platform to run application software ★ Simplified definition: software for the computer ★ System software = utility software + OS

What is utility software?

Utility software is software which focuses on the maintenance or administration of a part of the system

What are examples of system/utility software?

Examples of system/utility software: ★ Operating System (OS) ★ Antivirus ★ File manager

What is application software?

★ Exam-board definition: Application software is software that performs end-user tasks ★ Simplified definition: software for the suer

What are examples of application software?

Examples of application software: ★ Microsoft word ★ Microsoft Media Player ★ Microsoft Excel ★ Games e.g. Roblox

What are embedded systems?

Embedded systems are computer systems that are part of a larger system

What do embedded systems usually contain?

Embedded systems usually contain a control system

What are control systems?

Control systems monitor the desired outcome e.g. temperature of water in washing machine

What are the advantages of embedded systems?

Advantages of embedded systems: ★ (Usually) easier to design ★ Cheaper (to produce) ★ More efficient

What is a general purpose system?

General purpose systems are capable of performing many different tasks.

What is volatile memory?

Volatile memory is storage that is wiped clean when power is cut off from a device

What is non-volatile memory?

Non-volatile memory is memory that keeps its information after the power supply is cut.

What is RAM an abbreviation of? Why?

★ RAM is short for Random Access Memory ✔︎ This because it takes the same time to access different locations in memory

What is RAM?

Ram is: ★ The main memory in a computer ★ Where all applications are stored when used ★ When OS boots up, operating system gets copied from secondary storage to RAM ★ Software applications in secondary storage are copied into RAM when in use and stay RAM until the applications are closed

Is RAM volatile or non-volatile?

RAM is volatile

What are the main function of the operating system?

Main functions of the operating system: ★ Communicate with I/O devices ★ Provide a platform for the application to run on ★ To provide a user interface ★ Control memory management and allocation ★ Organise CPU and its processing tasks ★ Deal with file management and disk management ★ Manage system security and user accounts

What is ROM short for? Why?

★ ROM is short for Read Only Memory ✔︎ This is because it is memory which can only be read, not written

What is BIOS short for? Why?

★ BIOS is short for Basic Input Output System ✔︎ This is because it contains all instructions for the computer to properly boot up

What is ROM?

ROM is: ★ Comes on a small, factory-made chip built into the motherboard ★ Contains BIOS

What is firmware? What is an example?

★ Firmware is read-only software that provides basic instructions for the computer ✔︎ An example of firmware is ROM (Read Only Memory)

What takes more memory: RAM or ROM?

RAM needs more memory than ROM

Does BIOS take up much memory?

BIOS doesn't require much memory

What are the RAM and ROM requirements for a non-embedded system?

RAM and ROM requirements for a non-embedded system: ★ Usually need much more RAM than ROM ✔︎ Because they often need to write data into main memory ★ ROM is typically required for BIOS (which doesn't require much memory)

What are the RAM and ROM requirements for an embedded system?

RAM and ROM requirements for an embedded system: ★ Much more ROM than RAM ✔︎ Because they don't need to write much memory ★ They don't tend to have much secondary storage ✔︎ ROM is used to store all programs

How is overall performance affected by the amount of RAM?

How overall performance is affected by RAM: ★ If a computer has too little RAM ➜ It may not be able to keep all application data loaded at once 𐬽 Slowing the system down ★ The more RAM the computer has ➜ The more memory-intensive applications it can smoothly run 𐬽 Making the computer faster ★ If the user already has enough RAM to run everything smoothly ➜ Additional RAM will have no effect on performance

What is primary storage?

Primary storage is memory areas that the CPU can access directly

What are examples of primary storage?

Examples of primary storage: ★ CPU registers ★ Cache ★ RAM ★ ROM

What is secondary memory?

Secondary memory is: ★ Non-volatile memory ★ Which is not directly accessible by the CPU

What is typically stored in secondary memory?

All data that is not in use is stored in secondary memory e.g.: ★ Applications ★ User files ★ The OS

What are examples of magnetic storage?

Examples of magnetic storage: ★ Hard Disk Drives (HDDs) ★ Magnetic storage

True or false: Hard Disk Drive (HDD) and hard drive are synonyms

True, Hard Disk Drive (HDD) and hard drive are synonyms

How does a HDD work?

How a HDD (Hard Disk Drive) works: ★ There is a stack of magnetised metal disks spinning at a rate of 5400-15000rpm ★ Data is stored magnetically in small area called sectors within circular tracks ✔︎ Read/write heads on a moving arm are used to assess sectors on the disks

How can you counteract the fragility of HDDs?

Portable HDDs counteract the issue of the fragility in HDDs

How does magnetic tape work?

How a magnetic tape works: ★ Tapes are read/written sequentially (from beginning to end in order) by the tape drive

What are advantages and disadvantages of magnetic tape?

Advantages of magnetic tape: ★ High capacity ★ High storage for low cost ★ Extremely fast (when it is in the right place) ⚠︎︎ But slow to set up ★ Useful for large organisations backing up large stores of data

What are three examples of flash storage?

Two examples of flash storage: ★ Solid State Drives (SSDs) ★ USB pen drives ★ Memory cards e.g. SD cards

What is an example of a memory card?

An example of a memory card is an SD card

What is read/write life?

Read/write life is how many times data can be written before the Storage begins to deteriorate

How do SSDs work?

SSDs use electrical circuits to persistently store data

What are hybrid drives?

Hybrid drives: ★ Use SSDs for the the OS and programs ★ And a HDD for the data

Do portable SSDs exist?

Yes, portable SSDs exist which allows you to transport data

What are the disadvantages of other types of flash storage?

Other types of flash storage e.g. USB pen drives and memory cards are: ★ Much slower than SSDs ★ Have a much shorter read/write life

What are the advantages of other types of flash storage?

Advantages of other types of flash storage e.g. memory cards: ★ Can be used to expand storage for SMALLER devices e.g. cameras, smartphones (where SSDs and HDDs are too large ★ They have a very high capacity for their small size

What are the advantages of HDDs over SSDs?

Advantages of HDDs over SSDs, HDDs are: ★ Cheaper ★ Higher capacity (although SSDs do have a high capacity) ★ Longer read/write life (SSDs can only be written a certain amount of Tim's before they deteriorate)

What are the advantages of SSDs over HHDs?

Advantages of SSDs over HDDs, SSDs are: ★ Faster ★ Don't need de fragmenting ★ More shock-proof ★ Silent (HDDs make some noise) ★ Not fragile (unlike HDDs which have glass parts) 𐬽 SSDs are better portable devices

What is storage media?

Storage media is the physical material on which a computer keeps data, instructions, and information.

What is an example of storage media?

An example of storage media is optical discs

What is a storage device?

A storage device is a piece of computer equipment on which information can be stored.

What a re two examples of storage devices?

Two examples of storage devices: ★ HDDs (hard disk drives) ★ Optical drives

What are three examples of optical discs?

Three examples of optical discs: ★ CDs ★ DVDs ★ Blue-Rays

How much data can a CD store?

A CD can store around 700MB of data

How much data can a DVD store?

A DVD can store 4.7GB of data

How much data can a Blu-Ray store?

A Blu-Ray can store 25GB of data

What are the three forms of optical discs?

Three forms of optical discs: ★ Read-only e.g. CD-ROM ★ Write-once e.g. DVD-R ★ Rewritable e.g. BD-RW

Why are the use of optical discs declining?

The use of optical discs are declining as: ★ Streaming and download services have replaced them ★ Modern devices e.g. phones/tablets don't have optical drives ★ Low capacity ★ Very slow read/write speeds ★ RW discs have poor reliability ★ Easily scratched

What are the advantages of hard discs?

Advantages of hard discs: ★ Very cheap (per GB) ★ Portable ★ Won't be damaged by: ★ Water ★ Shocks

What is cloud storage?

Cloud Storage is a service where files can be uploaded via the Internet to a remote server (where it's usually stored on HDDs/SSDs)

Is cloud service typically free?

You normally have to pay a subscription for cloud service (some give you limited service for free)

What are eight advantages of cloud service?

Eight advantages of cloud service: ★ Users can access files from any device that has internet connection ★ Files can easily be shared or made public ★ Easy to increase/decrease amount of storage available based on amount of storage needed ★ No need to buy expensive hardware to store data ★ No need to pay IT stand to manage hardware ★ Cloud host (e.g. Apple with iCloud) provides: ★ Security for you ★ Backups for you ★ Can be cheap/free if little storage is required ★ Convenient for short-term storage

Rank storage devices based on average read/write speed (from slowest):

Ranking of storage devices based on average read/write speed (from slowest): 5) Optical disc 4) Memory card 3) Magnetic tape 2) HDD

1. SSD

Rank storage devices based on average cost (per GB, from slowest):

Ranking of storage devices based on average cost (per GB, from cheapest): 5) Magnetic tape 4) Optical discs 3) HDD 2) Memory card

1. SSD

Rank storage devices based on average capacity (from slowest):

Ranking of storage devices based on average read/write speed (from slowest): 5) Optical disc 4) Memory card 3) SSD 2) HDD

1. Magnetic tape

What are six disadvantages of cloud service?

Six disadvantages of cloud service: ★ Need internet connection to access files ★ Upload/download speed dependant on bandwidth ★ Dependant on host for: ★ Security ★ Backups ★ Stored data is vulnerable to hackers ★ Unclear who has ownership of cloud data ★ Subscriptions fees for iCloud are inconvenient in the long term

What does every I/O device require?

Every I/O device requires a device driver

What is a device driver?

A device driver acts as a 'translator' for the signals between the OS and the device

What will the OS do when a computer system is booted up?

When a computer is booted up, the OS will choose correct device drivers for the device it detects

What will the OS do if new devices are connected to the computer?

★ If new devices are connected to the computer ➜ The system may automatically find and install a new, matching driver

How are bugs fixed and improvements made on device drivers?

Bugs are fixed and improvements are made on device drivers via updates

What can hardware get access to via the OS?

The hardware can get access to the following things via the OS: ★ RAM ★ Secondary storage

What is a user interface (UI)?

The "User Interface" or UI of an app refers to how a person (user) interacts with the computer or app.

What UIs do most desktop computers use?

Most desktop computers use one of the following Graphical interfaces (GUIs) which are WIMP based (windows, icons, menus and pointers)

What does WIMP stand for?

Wimp stand for: ★ Windows ★ Icons ★ Menus ★ Pointers

How are user interfaces accessed?

★ If it is a computer, you may use the following to access UI: ★ Mouse ★ Keyboard ★ If it is a smartphone, you would use a touchscreen

What are advantages of particular types of OS?

Advantages of different types of OS: ★ Using windows and menus in WIMP based interfaces ★ Being able to tap, pinch and swipe on a touchscreen, mobile interface

What will the OS do when an application is opened?

When an application is opened, the OS will: ★ Copy the necessary parts of the application into memory ★ Add additional parts to memory if required ★ Remove parts of memory if they not being used

What decides how much RAM is used in an application?

The OS decides how much RAM is used in an application

Do all applications use the same amount of RAM? Give examples

No, all applications do not use the same amount of RAM: ★ An image editing software may require lots of RAM ★ A text editor won't require much RAM

What will the OS ensure if multiple applications are running at once?

If multiple applications are running at once, the application will make sure they don't overwrite or interfere with each other by keeping their processes in separate locations

What is a process?

A process has instructions that the CPU has to execute

How many instructions can a CPU execute at a time?

CPUs can only carry out instructions one process at a time

How do operating systems make sure tasks are done in an efficient order?

Operating systems use scheduling to make sure tasks are done in an efficient order

What is scheduling?

The process of scheduling: ★ Each process is allocated a priority. ✔︎ The CPU carries out these instructions from the top of the queue to the bottom of queue according to their priority ★ The OS may interrupt the CPU if a higher priority task becomes available ★ Allows for multitasking

What is multitasking in a computer?

Multitasking is when a computer switches between two tasks very rapidly ✔︎ This makes it look like these two tasks are being done simultaneously ✔︎ Remember, computers carry out billions of operations per second

How many operations does a computer do per second?

The computer does billions of operations per second

How does file mangagement work?

File management: ★ OS organises data into a hierarchal structure ★ Responsible for: of data ★ Movement ★ Editing ★ Deletion