Topic 1 Flashcards Preview

Computer Science > Topic 1 > Flashcards

Flashcards in Topic 1 Deck (41):

What does the CPU do?

Processes all of the data and instructions that make the system work.


What are the 3 mains parts of a CPU?

The control unit(CU)
The arithmetic logic unit(ALU)
The cache


What 3 parts effect CPU processing power?

Clock speed
Number of core
Cache size


What does the Control Unit(CU) do?

The control unit is in overall control of the CPU. It’s main job is to execute program instructions by following the fetch-decode-execute cycle.
It controls the flow of data inside (to registers, ALU, cache) and outside the CPU (to main memory and input/output devices).


What does the Arithmetic Logic Unit(ALU) do?

The ALU basically does all the calculations.
It completes simple addition and subtraction, compares the size of numbers and can do multiplications and divisions using repeated addition and subtraction.
It performs logic operations such as AND, OR and NOT and binary shifts — remember, computers process binary data.
It contains the accumulator register.


What does the Cache do?

The cache is a very fast memory in the CPU. It’s slower than the registers but faster than RAM.
It stores regularly in used data so that the CPU can access it quickly the next time it’s needed. When he CPU requests data, it checks that the cache first to see if the data is there. If not, it will fetch it from RAM.
Caches have a very low capacity and are expensive compared to RAM and secondary storage.
There are different levels of cache memory — L1, L2 and L3. L1 is the quickest with the least storage. L3 is the slowest with the most storage.


What is Von Neumann’s architecture?

A system where the CPU runs programs stored in memory. Programs consist of instructions and data which are stored in memory addresses.


What is the Fetch-Decode-Execute cycle?

Fetch - Copy memory address from the program counter in the MAR. Copy the instructions stored in the MAR address to the MDR. Increment the program counter to point to the address of the next instruction, ready for the next cycle.
Decode - The instruction in the MDR is decided by the CU. The CU may then prepare for the next step.
Execute - The instruction is performed. This could be: load data from memory, write data to memory, do a calculation or logic operation, change the address in the PC, or halt the program.


What are the two types of memory?

Volatile - Memory that is temporary. It requires power to retain its data.
Non-Volatile - Memory that is permanent it keeps its contents even when it has no power.


What is Random Access Memory(RAM)?

The main memory in a computer.
It can be read and written to. RAM is volatile.
It’s where all data, files and programs are stored while they’re being used.
When a computer boots up, the operating system is copied from secondary storage to RAM.
When software applications, documents and files are opened, they are copied. They stay in RAM until they are closed.


What is Virtual Memory?

As applications are opened, RAM fills with data.
When RAM is full, the computer needs somewhere else to put application data. It moves data that hasn’t been used recently to a location on secondary storage known as virtual memory.
If the CPU needs to read data stored in virtual memory, it must move it back to RAM.


What is Read Only Memory(ROM)?

ROM is non-volatile memory which can only be read from.
It contains all the instructions a computer needs to properly boot up. These instructions are called BIOS (Basic Input Output System).
As soon as the computer is powered on m, the CPU reads the instructions from ROM. This tells the CPU to do self checks and set up the computer.
ROM chips often use flash memory.


What is Clock speed?

This is the number of instructions a single processor core can carry out per second (Hz). For most computers, it’s about 3.5 GHz (3.5 billion instructions per second).
The higher the clock speed, the greater the number of instructions carried out per second.
Some CPUs can be overclocked to make them run at a higher clock speed than factory-set rate. It can be risky as it can cause CPUs to overheat, crash or permanent damage to the system. High performance cooling systems are needed.


What is Number of Cores?

Each core in a CPU can process data independently to the rest.
The more cores a CPU has, the more instructions it can carry out at once, so faster it can process a batch of data.
Most PCs and Smartphones have 4 or more cores.


What is Cache size?

The cache is data storage inside the CPU that’s much faster than RAM.
A larger CPU cache gives the CPU faster access to more data it needs to process.


What are Graphic Processing Units(GPUs)?

Specialised circuits for handling graphics and image processing. They relieve the processing load on the CPU, freeing it to do other things.
Computers have basic GPUs integrated onto the motherboard or the CPU. For better graphics a graphics card is used.
High-end graphics cards can improve performance-intensive applications e.g. PC gaming and design software.


What are the 3 tiers or storage?

Primary storage - The memory areas that the CPU can access very quickly, like CPU registers, cache ROM and RAM ( mostly volatile).
Secondary storage - Non-volatile storage, where all data (operating systems, applications and users files) are stored when not in use. It includes magnetic hard disk drives, solid state drives, CDs and SD cards.
Tertiary storage - Non-volatile storage used for storing data more long term. It’s mainly used for archives and back-ups of massive amounts of data. An typical example is magnetic tape library.


What are Hard disk drives(HDDs)?

Traditional internal storage in PCs and laptops.
A hard disk drive is made up of a stack of magnetised metal disks spinning at a rate between 5400 and 15000 rpm (revolutions per minute).
Data is stored magnetically in small areas called sectors within circular tracks. Read/write heads on a moving arm are used to access sectors on the disk.
Popular for backing up and transporting large amounts of data.
HDDs generally long lasting and reliable but are damaged with large impacts.


What are Solid State Drives(SSDs)?

Storage devices with no moving parts. Most of them use a type of flash memory. Purpose is internal storage.
SDDs have significantly faster read/write times than HDDs.
Hybrid drives exist that use solid state storage for the OS and programs, and a hard disk for data.
Examples are USB pen drives and memory cards used to expand storage capacity of small devices.


What’s are the advantages of HDDs and SSDs?

HDDs are cheaper.
Both are high capacity, but HDDs are higher.
HDDs have a longer read/write life than SDDs - SSDs start to deteriorate after certain number of times.
SSDs are faster.
SSDs don’t need defragmenting.
SSDs are more shock proof.
HDDs make some noise, SDDs are silent.


What are Optical discs?

Optical discs are CDs, DVDs and Blu-Ray discs.
CDs can hold around 700MB of data, DVDs can hold around 4.7GB and Blu-Ray can hold around 25GB.
Nowadays they are in decline due to streaming and download services like Netflix, ITunes and Steam.
Advantages are they are cheap (per GB), portable, and won’t be damaged by water or shocks.


What are the 3 types of Optical discs?

Read-only e.g. CD-ROM / DVD-ROM / BD-ROM
Write-once e.g. CD-R / DVD-R / BD-R
Rewritable e.g. CD-RW / DVD-RW / BD-RW


What are magnetic tapes used for and why?

Magnetic tapes has much greater storage capacity than HDDs. It also has an extremely low cost per
Used to by large organisations to store huge amounts of data.
It comes in plastic cassettes (containing reels of tape) which takes a special tape-drive to read/writing.
Tape is read/written sequently, meaning it is read/written from the beginning to the end. Causing it to be slow finding specific data.


What are the 5 main functions of a Operating System(OS)?

Communication between internal and external hardware.
Provide a user interface, allowing a user to interact with the computer and vice-versa.
Provide a platform for different applications to run.
Allow the computer to multi-task by controlling memory resources and the CPU.
Deal with file management and disk management.


What is the purpose of computers?

To take data, process it, then output it.
Computer were created to help process data and complete tasks more efficiently than humans.


What is hardware and software?

Hardware is the physical stuff that makes up your computer system, like the CPU, motherboard, monitor and printer.
Software is the programs or applications that a computer system runs e.g. an operating system, a word processor or game.


What are embedded systems and what do they do?

Embedded systems are computers built into other devices, like dishwashers microwaves and TVs. They are usually dedicated systems.
Embedded systems are often used as control systems — they monitor and control machinery in order to achieve a desired result.


What are the main internal hardware of a computer?

Power supply
Case cooling fan
CPU heat sink and cooling fan
Graphics card
RAM Sticks
Optical drive


How does the OS communicate with hardware?

Every piece of hardware connected to the computer system requires a device driver. Drivers essentially act as a ‘translator’ for the signals between OS and hardware.
When a computer is booted up, the OS will choose the correct device drivers for the hardware it detects. If a new hardware is connected to the computer, the system will install the new, matching driver.


How does the OS provide a user interface?

A user interface allows the user to interact with a computer system.
Graphical User Interfaces(GUIs) are the most common type as they are easy for everyday users by making them interactive and intuitive.
GUIs systems are optimised for specific input methods (e.g. Touchscreen devices).
A command-line interface is text based. The user enters specific commands to complete tasks. They are less resource-heavy and better for advanced users as they are far more efficient and powerful.


How does the OS manage resources?

Operating systems provide a platform to run applications ( by configuring hardware so they can use it, and giving access to the CPU and memory).
Operating systems that can run multiple applications at the same time are called multi-tasking OSs.
The OS moves necessary parts of the application to memory, followed by additional parts when required. The OS decides if the applications have been used frequently or not and is removed from memory.
A memory manager allocates certain applications certain memory addresses, to make sure their processes are placed in separate locations.
Only one application is processed by the CPU at a time. The OS divides CPU time between open applications and prioritise certain processes for efficiency.


How does the OS handle file and disk management?

The OS is responsible for file management - the organisation of data into usable hierarchical structure. It also deals with the movement, editing and deletion of data.
The OS manages the hard disk. It splits the physical disk into storage sectors, decides which sectors to write data to, and keeps track of free space on the disk. Ideally, the data for a single file would be placed in adjacent sectors, but this isn't always possible.
The OS also organises and maintains the hard disk with utility software like defragmentation software.


How does the OS manage user accounts?

Operating Systems can be single-user or multi-user. Single-user OSs (such as Windows 10 and OS X) allow one user to use the computer at once, whereas multi-user OSs (e.g. Unix server) allow several users to use the computer at the same time.
The OS is also responsible for user account control. User accounts allow different users to be granted access to specific data or resources on a computer system.
OSs may have anti-theft measures to prevent other users from accessing locked devices or accounts to steal information. User accounts may be password, or pin protected. Some devices also require a specific pattern on the screen, or have fingerprint or retina scanner.


How does defragmentation software work?

Files are stored on a hard disk drive in available spaces. Ideally, entire files would be stored together.
However, as files are moved, deleted and change size, lots of small gaps begin to appear on the disk. When writing files to the disk, the OS splits files into smaller blocks to fill up the gaps..
Overtime, the disk becomes more and more fragmented. This makes reading and writing files slower as the read/write head has to move back and forth across the disk.
Defragmentation software reorganises data on the hard drive to put fragmented files back together. It also moves files to collect all the free space together. This helps to prevent further fragmentation.
SSD's flash storage so fragmentation doesn't occur to them.


What at is a backup and what are the two types of backup?

A backup is a copy of a computer system's files and settings stored externally. This means data can be recovered in the event of data loss. Data loss can happen for many reasons... fire, theft, flood, malware, hardware failure.

Full backup - Where a copy is taken of every file on the system. They often use a lot of storage space. A full backup can take a long time to create, but is faster to restore.
Incremental backup - Where only the files created or edited since the last copied. They use less storage and are much quicker to create. But, a full system restore is slow - the last full backup must be restored, followed by every incremental backup since that point.


What is compression software?

Compression software reduces the size of files so they take up less disk space. It's used loads on the internet to make files quicker to download. Standard file formats include .zip and .rar. Compressed files need to be extracted before they can be used.


What is encryption software?

Encryption software scrambles (encrypts) data to stop third-parties from accessing it. Encrypted data can be decrypted using a special 'key'.


What is open source software?

Open source software is software where the source code is made freely available. Users may legally modify the source code to create their own spin-off software, which can be shared under the same licence and terms as the original software.
Well-known examples include Apache HTTP server (runs web servers), GIMP (image editing), Morzilla Firefox (web browser), and VLC media player.
Popular open-source software is always supported by a strong online community. Users actively help to improve software - anyone can play with the source code and suggest bugs and improvements to the original developers.


What are the advantages and disadvantages of open source code?

It is (usually) free.
Made for the greater good, not profit - it benefits everyone, encourages collaboration and sharing of ideas.
Software can be adapted by users ti fit their needs.
Wide pool of collaborators can be more creative and innovative than the programmers of one company.
Popular software is very reliable and secure - any problems are quickly solved by the community.

Small projects may not get regular updates, so could be buggy.
There may be limited user documentation.
No warranties if something goes wrong.
No customer support (although the community forums will usually make up for this).
Companies using open-source code to make custom software may not want competitors to see their source code, but they have no choice.


What is proprietary software?

Proprietary software is software where only the compiled code is released. The source code is usually a closely guarded secret.
Proprietary software licenses restrict the modification, copying and redistribution of the software. It's usually paid for.
Big companies producing proprietary software include Microsoft (Office, Windows, Outlook, etc.) and Adobe (Photoshop, Illustrator, etc.).


What are the advantages and disadvantages of proprietary software?

Comes with warranties, documentation, and customer support.
Should be well-tested and reliable as the company's reputation depends on this.
Fixes and updates will come regularly. (Open source will vary more).
Usually cheaper for companies than developing their own custom-built software.

Can be expensive.
Software may not exactly fit a user's needs, and they can't do anything about it.
Software companies may not maintain older software after warranties expire - they'll want people to buy their latest product.