computer systems Flashcards
1
Q
define hardware
A
the physical components that make up a computer system (including input/output storage devices, the CPU and RAM)
2
Q
define software
A
the non-physical programs that are stored by and run on a computer system
3
Q
describe the relationship between software and hardware
A
software makes use of physical hardware components and devices as the way of:
- taking inputs from users, outputting information to users and storing information
4
Q
what is system software; with examples
A
the software that provides a platform for other software to work e.g. operating systems and utility programs
5
Q
what is application software; with examples
A
any software added to the system that enables the user to perform a task e.g. web browsers, music and video players
6
Q
what are utility programs; with example
A
programs that perform extra functionality and tasks that keep computers running efficiently e.g. antivirus software
7
Q
what is an operating system; with example
A
software that manages computer hardware and software and supplies an interface for the user e.g. Microsoft Windows, google chrome
8
Q
what are operating systems responsible for managing
A
the processor(s), memory, input/output devices, applications and security
9
Q
how does the OS control processor management
A
it’s responsible for deciding which program will run on the processor and how much time it will get to run
10
Q
what is multi-tasking
A
where an OS manages many tasks happening at the same time e.g. web browser open whilst playing music and messaging friends
11
Q
what are interrupts
A
signals sent to the CPU by external devices to indicate an event that needs immediate attention
12
Q
how are hardware interrupts generated
A
by hardware devices e.g. printer out of paper
13
Q
how are software interrupts generated
A
by programs e.g. a divide-by-zero error will cause an error message to be displayed
14
Q
examples of high-level programming languages
A
python, Visual Basic, c#, java
15
Q
examples of low-level programming languages
A
assembly language, machine code
16
Q
s
A
17
Q
advantages of high-level languages
A
- easier to learn
- programs can be written faster
- it is easier to understand and debug
- it is closer to the language and syntax that we as humans understand
18
Q
why are most computer programs written in high-level languages
A
because they are easier to understand and are less complex than machine code
19
Q
what do processors do
A
they execute machine code; each type of processor has its own specific machine code instruction set
20
Q
what is the correspondence between assembly language and machine code
A
1:1
21
Q
what is assembly language
A
a low-level language which has to be translated into machine code before it can be executed
22
Q
what is assembly language used for
A
it’s often used to develop software for embedded systems and for controlling specific hardware components
23
Q
how are programs using assembly language made to be very efficient
A
they allow the programmer to precisely control any instruction on the processor
24
Q
what are high-level languages
A
programming languages that have a syntax we can understand; this makes them easier to learn and understand
25
compare assembly language and machine code
- assembly language allows a programmer to create programs more easily than writing in machine code
- each assembly language instruction maps directly to machine code
- programs written in assembly language must be translated to machine code in order to be executed
26
what is a translator and what are the three types
a translator program translates from one programming language to another one; the three types are interpreters, compilers and assemblers
27
what Is machine code
a low-level language that is expressed in binary and is specific to a processor or family of processors
28
function of a compiler
it translates a high-level language into machine code
29
function of an interpreter
another type of program that translates a high-level language into machine code
30
function of an assembler
it translates assembly code into machine code; they assemble source code so it can be run later
31
difference between interpreters and compilers
interpreters translate source code and immediately run it, but compilers compile source code so it can be run later
32
what do interpreters do instead of directly generating machine code
they call appropriate machine code subroutines within their own code to carry out commands
33
what is a bus
a collection of wires through which data/signals are transmitted from one component to another
34
function of the CPU
it processes instructions and runs one instruction at a time; it carries out billions of instructions per second
35
what is von Neumann architecture
a system where the program instructions and the data the programs are using are both stored in the same memory
36
what are registers
very fast small memory locations in the CPU that carry out operations for the control unit and the ALU; they temporarily store calculations
37
function of the ALU
performs arithmetic and logic operations on data
38
function of the control unit
it coordinates and controls all of the activities taking place within the CPU
39
how does the control unit carry out its function
- it decodes instructions and executes them
- it receives signals from the system clock
- it directs the timing and control of other parts of the CPU
40
function of the clock
it controls the timing of the processor
41
function of the clock
it controls the timing of the processor
42
how does the clock carry out its function
it switches between 0 and 1 several million times per second and synchronises all CPU operations
43
what is clock speed (AKA clock frequency)
the number of clock cycles which occur each second
44
the three buses that make up the system bus
address, data and control bus
45
function of the address bus
stores the address of the memory or device controller to be read from or written to
46
function of the data bus
it carries data throughout the computer system
47
function of the control bus
it uses control signals to control all activities within the CPU
48
how does the clock speed affect the performance of the CPU
the higher the clock speed, the more instructions the CPU will be able to execute per second; this equates to a better performance of the CPU
49
how does the number of processor cores affect the performance of the CPU
the more cores a CPU has, the more duplicate processing units are available to carry out the instructions. if many tasks are running simultaneously, multiple cores will result in a faster execution of instructions
50
how does the cache size affect the performance of the CPU
the more cache memory a CPU has, the more likely it is to be accessed from cache, which is much faster than revisiting RAM for the data
51
explain the fetch-execute cycle
- fetch; the next instruction is fetched to the CPU from main memory
- decode; the instruction is decoded to work out what it is
- execute; the instruction is executed - this may include reading/writing from/to main memory
52
when might multi-core processors not be advantageous
some softwares may not be programmed to take full advantage of multiple cores
53
what is cache
a small amount of very fast, expensive memory in the CPU
54
why is cache more advantageous than RAM
RAM is relatively slow memory to access and is further away from the processor than cache
55
what is RAM
it is the main place for storing instructions and data whilst a program is being executed; it's also called main memory
56
what is ROM
a flash memory chip that contains a small amount of non-volatile memory
57
define non-volatile
its contents cannot be changed and it retains its memory after the computer is turned off
58
define volatile
all the memory content is lost when the power is interrupted or switched off
59
define main memory
any form of memory that is directly accessible by the CPU, except for cache and registers
60
define secondary storage
any non-volatile storage mechanism not directly accessible by the CPU
61
why is primary storage needed in von neumann architecture
to store programs that are currently running and need to be accessed by the CPU
62
what does RAM normally store
- the operating system (or part currently in use)
- the software currently in use
- the data which the software is using
63
where does the name Random Access memory come from
the ability of the CPU to access any part of the memory in the same amount of time
64
what''s faster to access, RAM or a hard drive
RAM
65
describe how RAM is volatile
the computer stores running programs and data in RAM when your computer is turned on. when it turns off, data stored in RAM is lost; it loses data if the power is off
66
describe how hard drives are volatile
all your programs and data are stored permanently on your hard drive; it doesn't lose the data if the power is off
67
describe how ROM is used to store data
some data needs to be permanently held in primary storage, even when a computer has no power; ROM stores this, as data isn't lost if the power is off
68
differences between RAM and ROM
- RAM has a lot more storage space than ROM
- RAM is used to store running programs and operating system, ROM is used to store BIOS and bootstrap
- you can read and write to RAM, but you can only read ROM
- RAM is volatile, ROM is not
69
what is ROM used to store
- the initial program that is run when the computer is turned on (the bootstrap)
- it tells the computer where it will find the operating system on the hard drive
- stores the basic input/output system (BIOS)
70
function of the BIOS
controls basic technical configuration of the computer such as the processor speed and system time; it can run without a hard drive or other secondary storage being present
71
what is secondary storage
a type of storage where the data remains when there is no power; non-volatile
72
examples of secondary storage
hard drives, DVD drives, CD drives, removable flash media (USB stick/SD card)
73
two types of primary storage
RAM and ROM
74
differences between main memory and secondary storage
- main memory is volatile (RAM), secondary storage is non-volatile
- main memory is very fast to read/write, secondary storage is very slow to read/write
- main memory is expensive, secondary storage is cheap
- main memory stores data and programs currently in use by the computer system, secondary storage permanently stores data to be used when needed
- main memory is directly accessible by CPU, secondary storage is not directly accessibly by CPU
75
what is memory
it refers to RAM; it is volatile and can be directly accessed by the CPU
76
what is a USB
a type of storage device that is non-volatile but cannot be directly accessed by the CPU
77
what is storage
devices that keep the data even when the computer is turned off (non-volatile)
78
uses of secondary storage
- programs and data are stored on hard drive
- blu-rays may be used to distribute films
- memory sticks may be used to transport data from one place to another
- magnetic tape or external hard drives may be used for backup
- SD cards can be used for additional storage on cameras and smartphones i.e. for music, videos and photos
79
how does magnetic storage work
mechanical parts move over the disks surface to read and write data magnetically, or a drive head reads a magnetic tape
80
how does optical storage work
lasers read and write data using light
81
how does solid state storage work
data is recorded onto solid memory chips without any moving parts
82
features of magnetic disks
- they have disks which contain concentric circles called tracks
- each track is divided into sectors
- disk heads mounted on mechanical arms read and write the data
83
what is a hard disk
a disk with a solid platter
84
features of a hard disk
- they have a magnetic platter which contains the data
- the drive read/write head reads data on the drive
- the drive spindle rotates
- the actuator moves the read/write arm
85
pros and cons of magnetic storage
ADVANTAGES:
- cheap
- large storage capacities
-relatively fast write speed
DISADVANTAGES:
- lots of mechanical parts
- not very durable
- sealed unit due to the disk head and platter precision
- it isn't very portable
86
uses of magnetic storage
for storing large quantities of data on personal computers
87
features of optical disks
- the data is stored as pits and lands burnt or pressed into a spiral track circulating outwards from the centre
- a laser beam passes over the pits and lands; the level of reflection is measured
- from this signal, 0s and 1s can be derived
88
pros and cons of optical storage
ADVANTAGES:
- cheap
- very easily portable
- takes up little space physically
DISADVANTAGES:
- less storage capacity compared to other types
- easily damaged/scratched
- requires a CD reader
- slow write speeds
89
uses of optical storage
storing songs, videos and other multi-media storage; backup and archiving of data
90
features of solid state drives
- they use non-volatile flash memory to store information
- they have very fast read/write speeds as they don't need to wait for a disk to spin to the correct location and an arm to move
- no mechanical or moving parts meaning these disks are very durable
91
how does flash memory work
a large electric current is used to force electrons through a barrier and trap them on the other side; they remain on the other side until flashed with a new current; trapped = 0, not trapped = 1
92
pros and cons of SSDs
ADVANTAGES:
- highly durable because there's no moving parts
- very fast read/write speeds
- no noisy fan or drive arm
- faster start up times
- large storage capacity
DISADVANTAGES:
- more expensive than magnetic hard disks
93
what storage does cloud storage use
magnetic and/or solid state storage at a remote location
94
pros of cache
ADVANTAGES:
- stores recently used data so is available extremely quickly
- accesses data faster than RAM
DISADVANTAGES:
- can only hold a small amount of memory
- expensive
95
what is cloud storage
saving data in an off-site storage system maintained by a third party, e.g. dropbox, google drive
96
how does cloud storage work
- data is saved at servers to a remote location
- these servers can use magnetic and/or solid-state storage
- the data is accessed via the internet
97
why would cloud storage make use of multiple copies of the same data stored at different locations
if one data centre had a fire, the data could be accessed from another
98
how can some cloud storage meet data protection requirements
some providers may let the customer choose which country the data is stored in
99
pros of cloud storage
- easy to use
- high data storage capacity
- convenient to use; users can access data from anywhere with an internet connection
- backups are carried out by the cloud provider so saves the need for local backups
- data storage capacity can be increased easily if the user needs more
100
cons of cloud storage
- data cannot be accessed without an internet connection
- uploading and downloading data could take a long time
- the user has to pay more money to increase storage capacity
- security and privacy concerns with some providers
101
what is an embedded system
a computer system that uses programmed processors embedded onto a single circuit board; a single microprocessor with RAM, ROM and the CPU. used to control a device using simple inputs
102
how are embedded systems adapted to their function
they're designed to carry out a small number of specific tasks very efficiently
103
examples of embedded systems
watches, mobile phones, fitness trackers, pacemakers etc
104
pros of embedded systems
- they're highly efficient at performing tasks
- they're extremely reliable
- they're easy to design
- they're cheap to produce
- they're compact in size
- they're low in power consumption
105
cons of embedded systems
- they're slow
- new software can't be installed on them
106
difference between embedded and non-embedded systems
a standard OS creates an environment where a user and the computer may interact with one another to perform a huge variety of tasks; an embedded system, however, will only perform one type of task, and it will often do it without any, or little, user intervention
107
examples of non-embedded systems
desktop PC, laptop
108
examples of non-embedded systems
desktop PC, laptop
