Section 1 - components of a computer system Flashcards
1
Q
what is the purpose of a computer?
A
to take data, process it, then output it
2
Q
what does a computer consist of?
A
hardware and software that work together to process data or complete tasks
3
Q
what is hardware?
A
the physical parts of a computer system, like the CPU, motherboard, monitor and printer
4
Q
what is software?
A
the programs or applications that a computer system runs e.g. an operating system, a word processor or video game
5
Q
what are peripherals?
A
external pieces of hardware like the keyboard, mouse and printer
6
Q
what are embedded systems?
A
computers built into other devices, like dishwashers, microwaves and TVs. they are usually dedicated systems
7
Q
what are embedded systems often used as?
A
control systems - they monitor and control machinery in order to achieve a desired result
8
Q
what are the advantages of an embedded system over a general purpose computer?
A
they’re dedicated to a single task, so they are usually easier to design, cheaper to produce, and more efficient at doing their task
9
Q
what are the components of a computer?
A
power suply case cooling fan CPU heat sink and cooling fan CPU graphics card hard disk drive motherboard RAM sticks optical drive
10
Q
what does the power supply of a computer do?
A
supplies power to the motherboard, optical and hard drives, and other hardware
11
Q
what does the case cooling fan of a computer do?
A
extracts hot air from the computer case
12
Q
what does the CPU heat sink and cooling fan of a computer do?
A
it keeps the CPU at a steady temperature
13
Q
what does the CPU of a computer do?
A
it does all the processing
it is the most important component
14
Q
what does the hard disk drive of a computer do?
A
its internal secondary storage
15
Q
what does the motherboard of a computer do?
A
its the main circuit board in the computer, where the hardware is connected
16
Q
what does the optical drive of a computer do?
A
for read/writing of optical discs
17
Q
what is a CPU?
A
the brain of a computer
it processes all of the data and instructions that make the system work
18
Q
what does the processing power of a CPU depend on?
A
characteristics like:
clock speed
number of cores
cache size
19
Q
what are the 3 main parts of the CPU?
A
the control unit
the arithmetic logic unit
the cache
20
Q
what does the control unit do?
A
its main job is to execute program instructions by following the fetch-decode-execute cycle.
it controls the flow of data inside and outside the CPU
21
Q
what does the arithmetic logic unit do?
A
it does all the calculations
it completes simple addition and subtraction, compares the size of numbers and can do multiplication and division using addition ad subtraction
it performs logic operations like AND, OR and NOT and binary shifts
it contains the accumulator register
22
Q
what is the cache?
A
very fast memory in the CPU. slower than registers, faster than RAM
it has low capacity and is expensive compared o RAM and secondary storage
there are 3 different levels of cache memory (L1, L2, L3) they get slower but can hold more as the levels increase
23
Q
what does cache do?
A
it stores regularly used data so the CPU can access it quickly, the CPU checks the cache for the data it wants before RAM
24
Q
what does von neumann architecture describe?
A
it describes a system where the CPU runs programs stored in memory
25
how is the von neumann architecture laid out?
data goes in to the CPU from input devices and memory and out to output devices and the memory. inside the control unit, registers and ALU are all connected
26
what do registers do?
they temporarily hold tiny bits of data needed by the CPU. they're very quick to read/write to
27
what does the control unit contain?
the program counter
28
what does the ALU contain?
accumulator
29
what does the registers contain?
memory address register
| memory data regiser
30
what does the MAR do?
it holds any memory address about to be used by the CPU. the address might point to data or a CPU instruction
31
what does the MDR do?
it holds data or instructions. this may have been fetched from memory, or be waiting to be written to memory
32
what does the accumulator do?
it stores intermediate results of calculations in the ALU
33
what does the program counter do?
it holds the memory address of the instruction for each cycle
34
what happens in the fetch part of the fetch-decode-execute cycle?
copy memory address from program counter to MAR
copy the instruction stored in the MAR address to MDR
increment program counter to point to the address of the next instruction, ready for the next cycle
35
what happens in the decode part of the fetch-decode-execute cycle?
the instruction in the MDR is decoded by the CPU. the CPU may then prepare for the next step, e.g. by loading values into the MAR or MDR
36
what happens in the execute part of the fetch-decode-execute cycle?
the instruction is performed. this could be: load data from memory, write data to memory, do a calculation or logic operation (using the ALU), change the address in the PC, or halt the program
37
what is RAM?
random access memory that is used as the main memory in a computer. it can be read and written to. it is volatile.
38
what is volatile memory?
temporary memory. it requires power to retain its data
39
what is non-volatile memory?
permanent memory - it keeps its contents even when it has no power
40
what is main memory?
where all data, files and programs are stored while they are being used
41
what happens when a computer boots up?
when the operating system (software applications, documents and files) are opened, they are copied from secondary storage to RAM. they stay in RAM until the files or applications are closed
42
how fast is RAM?
it is slower than the CPU cache, but much faster than secondary storage
43
what happens 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
44
why might virtual memory be used?
if there are too many applications open at once, or if a particularly memory-intensive application is being used
45
why is virtual memory bad?
the CPU needs to read data stored in virtual memory so it has to be moved back to RAM. this is slow because data transfers are slower on secondary storage than RAM.
it makes a computer slow to respond when switching between applications or when using a memory-intensive application
46
how can an application be memory-intensive?
due to data constantly moving between virtual memory and RAM just to keep the program running
47
what is ROM?
read only memory, its non-volatile memory. it can only be read and not written to.
it comes on a small, factory-made chip built into the motherboard
48
what does ROM contain?
all the instructions a computer needs to properly boot up. these instructions are called the BIOS
49
what is the BIOS?
basic input output system. its a type of firmware which is hardware-specific software built in to a device. embedded systems are controlled by firmware
50
what happens when a computer is powered on?
the CPU reads the instructions from the ROM. this tells the CPU to perform self checks and set up the computer. e.g. test the memory is working, see what hardware is present, copy the operating system to RAM
51
how can the BIOS on a ROM chip be updated?
ROM chips often use flash memory. this is a common non-volatile memory that stores data in electrical circuits by trapping electrons. its used in SD cards, USB sticks and solid state drives.
52
what is clock speed?
the number of instructions a single processor core can carry out per second (Hz). usually around 3.5 GHz
53
what does overclocked mean?
CPU's can be overclocked to make them run at a higher clock speed than the factory-set rate. it's risky if not done properly - it can make CPU's overheat, causing crashes or permanent damage to the system. high performance cooling systems are usually needed
54
what do cores do?
each core can process data independently of the rest. the more cores, the more instructions that can be carried out at once, so the faster data can be processed.
most computers and phones have 4 cores now
55
how can more RAM affect a computer?
more applications or more memory-intensive applications can run smoothly, so it is faster
RAM can be upgraded by replacing RAM sticks with higher capacity ones
this may make no difference if the computer already has lots of RAM
56
what is a GPU?
graphics processing unit. these are specialised circuits for handling graphics and imaging processing. they relieve the processing load on the CPU, freeing it to do other things
57
why might better GPU's be used?
computers have basic GPU's integrated onto the motherboard or the CPU. for better graphics performance, a dedicated GPU is often used.
high-end graphics cards can improve performance in graphics-intensive applications. e.g. PC gaming and design software
58
what are the 2 main tiers of software?
primary storage
| secondary storage
59
what is primary storage?
the parts of memory that the CPU can access very quickly, like the CPU registers, cache, ROM and RAM. it has the fastest read/write speeds and is mostly volatile
60
what is secondary storage?
its non-volatile - its where all data is stored when not in use. it includes magnetic hard disk drives, solid state drives, CDs and SD cards. Read/write speeds are much slower compared to primary storage
61
what is tertiary storage?
its used for long term data storage (its mainly used for archives and back-ups of massive amounts of data)
62
what are hard disk drives?
the traditional internal storage in PCs and laptops. they're made up of a stack of magnetised metal disks spinning at a rate between 5400 and 15000 rpm
63
how is data stored on HDDs?
they're stored magnetically in small areas called sectors within circular tracks. read/write heads on a moving arm are used to access sectors on the disks
64
what are portable HDDs used for?
backing up and transporting large amounts of data
65
what are pros and cons of HDDs?
pros - long lasting, reliable
| cons - have moving parts, can be damaged by large impacts like being dropped
66
what are solid state drives?
storage devices with no moving parts. most of them use a type of flash memory. they are used for internal storage like HDDs
portable SSDs can be used to back up and transport data
67
what are hybrid drives?
they use solid state storage for the OS and programs, and a hard disk for data
68
what are other types of flash storage other than SSDs and HDDs?
USB pen drives and memory cards are also flash-based, solid-state storage
they're slower than SSDs and have shorter read/write cycle life
69
what are USB pen drives and memory cards used for?
to expand the storage capacity of small devices like cameras, smartphones and tablets. their capacity is very high relative to their tiny size
70
what are the advantages of HDDs over SSDs?
they are cheaper
both have high capacity, but HDDs are higher
they have a longer read/write cycle - SSDs can only be written a certain number of times before they begin to deteriorate
71
what are the advantages of SSDs over HDDs?
they are faster
they don't need defragmenting
they are more shock-proof than HDDs
HDDs make some noise, SSDs are silent
72
what are some examples of optical discs?
CDs, DVDs and Blu-ray discs
73
how big are different optical discs?
CDs - 700 MB
DVDs - 4.7 GB
Blu-ray - 25 GB
74
what are the 3 forms of optical disc?
read-only (CD-ROM, DVD-ROM, BD-ROM)
write-once (CD-R, DVD-R, BD-R)
re-writable (CD-RW, DVD-RW, BD-RW)
75
why is the use of optical discs decreasing?
internet speeds have increased, so streaming and download services don't need optical devices
modern devices like phones and tablets don't have optical devices
DVD-Rs and RWs were popular for backing up data, but they can't compete with flash storage devices due to their low capacity per disc, very slow read/write speeds and poor reliability of RW discs
76
what are the advantages of magnetic tape?
it has more storage capacity than HDDs, it is also cheap per GB.
77
what is magnetic tape used for?
large companies use magnetic tape in archive libraries to store huge amounts of data. it comes in plastic cassettes that require a special tape-drive for read/writing
78
how is magnetic tape read/written?
sequentially (from beginning to end) or until it is stopped by the computer. this means it is slow when finding specific data stored on it, but has fast read/write speed once it is in the correct place to begin
79
what are the average read/write speeds of different types of storage from fastest to slowest?
```
SSD
HDD
magnetic tape
memory card
optical disk
```
80
what are the average costs of different types of storage from priciest to cheapest?
```
SSD
memory card
HDD
optical disk
magnetic tape
```
81
what is the average capacity of different types of storage from highest to lowest?
```
magnetic tape
HDD
SSD
memory card
optical disk
```
82
what are the main functions of an operating system?
communicate with internal and external hardware via device drivers
provide user interface
provide a platform for applications to run on
allow computer to multi-task by controlling memory resources and the CPU
deal with file management and disk management
mange security of the system
83
what is user interface?
allowing users to interact with the computer
84
what are device drivers?
they act as a translator for the signals between OS and hardware. all hardware connected to the computer system requires one
85
how does the operating system communicate with device drivers?
when a computer is booted up, the OS will choose the correct device drivers for the hardware it detects. if new hardware is connected to the computer, the system will install the new, matching driver
86
why do device manufacturers release updates to device drivers?
in order to fix bugs, add features or improve the performance of their hardware. updates may be installed automatically by the OS or manually by the user
87
what is the most common type of user interface?
GUI's (graphical user interfaces)
88
what are graphical user interfaces designed for?
they are designed to be easy for everyday users by making them visual, interactive and intuitive
89
what are different GUI's used for?
WIMP-based GUI's use windows, icons, menus and pointers
android and iOS were created for touchscreen devices, using finger gestures like pinching and swiping in place of a mouse
90
what is a command-line interface?
it is text based. the user enters specific commands to complete tasks. they are less resource-heavy than GUI's. they aren't suitable for everyday users. advanced users can be far more efficient and powerful than a GUI. they can be used to automate processes using scripts
91
what are multi-tasking OS's?
operating systems that can run multiple applications at the same time. they help the CPU carry out multi-tasking by efficiently managing memory and CPU processing time
92
what does the OS do when an application is opened?
it moves the necessary parts of the application to memory, followed by additional parts when they are required. the OS will decide if applications or features have been used recently - if not, they may be removed from memory
93
what does the OS need to do to run multiple applications?
it needs to make sure that the applications don't overwrite or interfere with each other.
94
what does a memory manager do?
it allocates certain applications to certain memory addresses, to make sure their processes are placed into separate locations
95
does the CPU process multiple applications at once?
no, 1 is processed at a time and the other processes have to wait. the OS divides CPU time between open applications and may prioritise certain processes in order for instructions to be executed in the most efficient order
96
how can the OS help the CPU to carry out multi-tasking?
it moves necessary parts of an application to memory
makes sure applications don't interfere
the CPU switches between tasks very quickly
the OS can organise the movement of data to and from virtual memory
97
what do file extensions do?
they tell the computer which software should be used to open the file. which could be images, music, videos or spreadsheets
98
what is file management?
the organisation of data into a usable hierarchical structure. it also deals with the movement, editing and deletion of data
99
how does the OS manage 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. the data for a single file would be placed in adjacent sectors, but this isn't always possible
100
how does the OS include utility software?
it helps it to manage files and disks. e.g. file compression software, encryption, defragmentation
101
what is file compression software?
it can reduce the size of individual files
102
what is encryption software used for?
to secure the contents of files
103
what is defragmentation software?
it can help to organise and maintain the hard disk by collecting all the free space together
104
what are single-user operating systems?
they allow only one user to use the computer at once. e.g. windows 10 and OS X, even if the computer has multiple user accounts, or is connected to a network
105
what are multi-user operating systems?
they allow several users to use the computer at the same time. they're often used on mainframes and give many users simultaneous access. e.g. UNIX server and ATM's allow thousands of people access to a large bank's mainframe at the same time
106
what do user accounts do?
they allow different users to be granted access to specific data or resources on a computer system
107
how can users access their data on most desktop operating systems?
each user has access to their own personal data and desktop, but can't access other users personal data.
108
how can operating systems protect user data?
they 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 user to draw a specific pattern on the screen, or have fingerprint or retina scanners
109
how do files become fragmented?
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
110
why is fragmentation bad?
ideally, entire files would be stored together. fragmentation makes reading and writing files slower as the read/write head has to move back and forth across the disk
111
what does defragmentation software do?
it 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 prevent further fragmentation
112
why doesn't fragmentation work on SSDs?
SSDs use flash storage with no moving parts, fragmentation doesn't cause problems because they can access data just as quickly no matter how its arranged. SSDs have a limited number of read/writes, defragmenting can shorten their lifespan
113
what is a backup?
a copy of a computer system's files and settings stored externally. this means data can be recovered in the event of data loss.
114
why does data loss happen?
```
fire
theft
flood
malware
hardware failure
accidental deletion
```
115
what is a backup utility?
software with facilities such as scheduling of regular backups, creating rescue disks, disk images, and options for full or incremental backups
116
what is a full backup?
this is where a copy is taken of every file on the system. they often use a lot of storage space
117
what is an incremental backup?
where only files created or edited since the last backup are copied.
118
pros and cons of full backup:
it can take a long time to create, but is faster to restore from
119
pros and cons of an incremental backup:
use less storage space and are much quicker to create. but a full system restore is slow - the last full backup must be restored, followed by every incremental since that point
120
what does compression software do?
it reduces the size of files so they take up less disk space. standard file formats include .zip and .rar. compressed files need to be extracted before they can be used
121
where is compression software used?
on the internet to make files quicker to download.
122
what does encryption software do?
it scrambles data to stop third-parties from accessing it. encrypted data can be decrypted with a key
123
what is open source software?
software with a freely available source code. users can legally modify the source code to create their own spin-off software, which can be shared
124
what are good examples of open source software?
Apache HTTP server - runs web servers
GIMP - image editing
Mozilla Firefox - web browser
VLC media player
125
what is LINUX?
a hugely successful open source OS released in 1991. hundreds of LINUX-based OSs have been developed and shared over the years e.g. UBUNTU, Debian and Android
126
what are the advantages of open source software?
usually free
non-profit - it benefits everyone, encourages collaboration, sharing of ideas
can be adapted to fit users needs
lots of collaborators can be more creative and innovative than the programmers of 1 company
popular software is very reliable and secure - any problems are quickly solved by the community
127
what are the disadvantage of open source?
small projects may not get regular updates, so could be buggy or have unpatched security holes
may be limited user documentation
no warranties if something goes wrong
no customer support
companies using open source may not want competitors seeing their source code but have no choice
128
what does most popular open source software have?
a strong online community (forums of users sharing ideas and solving problems). users actively help to improve software - anyone can play with open source code and suggest bug fixes and improvements to the original developers
129
what is proprietary software?
its usually paid for, where only the compiled code is released. the source code is usually a closely-guarded secret. it licenses restrict the modification, copying and redistribution of the software
130
why do businesses use proprietary software?
they often use proprietary instead of open source because it tends to have better customer support options.
131
what are some popular examples of companies that use proprietary?
Microsoft (office, windows, outlook, etc.) and Adobe (Photoshop, illustrator, etc.)
132
advantages 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
usually cheaper for companies than developing their own custom-built software
133
disadvantages of proprietary 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
