Components of a computer system (PAPER 1) Flashcards
What is a computer
A machine that processes data
What is the purpose of a computer
to take data, process it and then output it
What does a computer system consist of
hardware and software that work together to process data and complete tasks
What is hardware
physical things that make up a computer system
What is software
programs or applications that a computer system runs
What are external pieces of hardware known as
peripherals
What is a general purpose computer
a computer designed to perform many tasks
What is a dedicated system computer
a computer designed to perform one particular function
What is an embedded system
a computer inside a larger system
What are the two types of computer
general purpose and dedicated system
What type of computer do embedded systems tend to be
dedicated system
What is a control system
a system that monitors and controls machinery in order to achieve a desired result
What are the advantages of using a dedicated system instead of a general purpose computer
- cheaper to produce
- easier to design
- more efficient
What are nine key parts to a desktop PC
- power supply
- case cooling fan
- CPU heat sink, cooling fan
- CPU
- Graphics card
- Motherboard
- Hard Disk Drive
- RAM
- Optical Drive
What is the purpose of a power supply
supplies power to motherboard and other hardware
What is the purpose of a case cooling fan
to extract heat from the computer case
What is the purpose of a CPU heat sink and cooling fan
to keep the CPU at a constant temperature
What is the motherboard
The main circuit board where hardware is connected
What is the optical drive used for
for read / writing optical discs
What does CPU stand for
Central Processing Unit
What is the overall job of the CPU
to process the data and instructions that make the system work
What are the two main types of architecture of CPU
Harvard and Von Neumann
What are the three main parts of the CPU
- control unit
- Arithmetic Logic Unit
- Cache
What are the two main jobs of the control unit
- manage fetching, decoding, execution of program instruction
- control the flow of data inside and outside the CPU
What does the ALU do
- additions and subtractions
- multiplying/ division using add/subtract
- comparing size of numbers
- logic operations e.g. AND, OR, NOT
- binary shifts
What is the Cache
very fast memory in the CPU
How does the cache’s speed compare to other forms of memory
slower than registers, faster than RAM
What is the cache used for
to store regularly used data for quick access - CPU checks cache first before going to RAM
What is the drawback of using cache
it has a low capacity and is very expensive
What are the three levels of cache memory, how do they compare
- L1 - quickest, lowest capacity
- L2 - slower, larger capacity
- L3 - slowest, largest capacity
- What do registers do
- How fast are they
- What are the four key types
hold tiny bits of data needed by the CPU
very fast to read / write
- program counter
- memory address register
- memory data register
- accumulator
Where is the accumulator stored
in the ALU
What is the ALU
arithmetic logic unit
What is the CU
control unit
When and who created the Von Neumann architecture
John Von Neumann in 1945
What do programs consist of
instructions and data stored in memory addresses
What does PC stand for (register)
program counter
what does the PC do
holds the memory address of the instruction for each cycle
What does the accumulator do
stores the intermediate results of calculations in the ALU
What is a key feature special to the Von Neumann architecture
it only uses one memory for both the data and the instructions
What does MAR stand for
memory address register
What does MDR stand for
memory data register
What does the MAR do
holds any memory address about to be used by the CPU
What does the MDR do
holds the actual data or instruction. This may have been fetched from memory , or be waiting to be written to memory
What does the memory hold in a Von Neumann system
program instructions and program data
What holds the PC
Control Unit
What happens during the Fetch Instruction in a Fetch - Execute cycle
- Copy memory address from program counter to MAR
- Copy the instruction stored in MAR address to MDR
- increase program counter to point to address of next instruction ready for next cycle
What happens during the Decode Instruction in a Fetch - Execute cycle
instruction in MDR is decoded by CU
What happens during the Execute Instruction in a Fetch - Execute cycle, give examples
instruction is performed.
- load data from memory
- write data to memory
- change address in PC
- halt program
- do caclulation / logic operation in ALU
What is RAM
high speed, volatile memory
what does RAM stand for
Random Access Memory
What is volatile memory
memory that requires power to retain data
what is non-volatile memory
memory that doesn’t require power to retain data
can RAM be read and written to
YES
What happens in main memory
main memory (RAM) is where all data, files and programs are stored while being used
What happens to RAM when the computer boots up
OS is copied from secondary storage to RAM
When are applications, documents and files in RAM
when they are opened until they are closed
How does the speed of RAM compare to other forms of memory
slower than cache but much faster than secondary storage
What is virtual memory
secondary storage used as extra RAM
where is application data put when RAM is full
virtual memory
How does the CPU read data stored in virtual memory; how fast is this process
the data is moved to RAM
It is slow because transfer rates are slower on secondary storage
what does ROM do
tells the computer how to boot up
What does ROM stand for
Read Only Memory
What is ROM
non volatile memory that can only be read
Where in the computer is the ROM
on a small chip in the motherboard
What is BIOS, what does it stand for
- instructions needed for a computer to properly boot up
- Basic Input Output System
What instructions does the ROM provide after booting up
to perform self-checks and set up the computer
is it possible to update BIOS on a ROM chip
YES
What 3 factors does CPU performance depend on
- Clock Speed
- Number of Cores
- cache Size
What is clock speed
the number of instructions a single processor core can carry out per second
What is clock speed measured in
Hz
What is the relation between clock speed and instructions carried out per second
the higher the clock speed, the more instructions can be carried out per second
What is the danger of making CPUs run at higher clock speeds that the factory set rate
how can the risk be reduced
- overheating
- crashes or permanent damage to systems
The risk can be reduced with high performance cooling systems
what is the relation between number of cores and instructions carried out at once
the more cores, the more instructions able to be carried out at once
How many cores do most PCs and smartphones have these days
4 or more
How does the amount of RAM affect the functionality of the system
the more RAM, the smoother and faster the software
What does GPU stand for
Graphics processing units
What are GPUs
specialised circuits for handling graphics and image processing
What are the two main types of storage and what are their properties
- primary storage - memory which CPU can access quickly, fast, mostly volatile
- secondary storage - non volatile, slower
What are the 4 types of secondary storage
- Hard disk Drives
- Solid state drives
- optical discs
- magnetic tapes
What are hard drives, how do they work and what are their benefits
- traditional internal storage, can be portable.
- data is stored magnetically in circular tracks
- a movable arm accesses these and can read / write it
- long lasting and reliable, can be damaged by large impacts
- cheaper, high capacity, unlimited read/ write cycles
What are Solid state drives, how do they work and what are their benefits
- no moving parts
- fast read / write times
- limited read / write cycles, relatively expensive
- electrons give off binary data
What are examples of optical discs
CDs, DVDs, Blu-ray
What is storage media
things that hold data e.g. optical discs
What is a storage device
something that read/writes data to media e.g. optical DRIVES
How do the capacities of (CDs, DVDs, Blu-ray) compare
blu-ray is largest (25GB)
DVDS (4.7GB)
Cds(700MB)
What are the three forms of optical discs, what are their notations
Read only (e.g. CD-ROM)
Write - once (e.g. CD-R)
rewritable (e.g. CD-RW)
What are the advantages of Optical discs
very cheap, portable, undamaged by water / shocks
What does OS stand for
operating system
What are the main purposes of an OS
- communicate with internal and external hardware
- provide a User Interface
- allows multi-tasking
- handles file and disk management
- deal with user accounts
What is a device driver
a software which acts as a translator for the signals between OS and hardware
What are the two types of UI
- graphical user interface
- command line interface
What does UI stand for
user interface
What does GUI stand for
graphical user interface
What does CLI stand for
Command line interface
What does WIMP stand for
Windows, ICons, Menus, pointers
What are two common touchscreen GUIs
Android and IOS
What is CLI
text based UI - specific commands are entered
What are the benefits of GUI and CLi
- GUI is easier to use
- CLI is much faster, less resource heavy
What is a script
a simple program
What are OSs that can run multiple applications at once called
multitasking OSs
how does the OS help the CPU multitask
- managing memory
- managing CPU process time
What does the OS need to make sure of in order to run multiple applications
they don’t overwrite or interfere with each other
What does a memory manager do
allocate certain applications certain memory addresses so their processes are placed into separate locations
how does OS manage CPU time
divides CPU time between open applications, can prioritise certain processes to maximise efficiency
What do memory buffers do
help manage the flow of data - stores data until component / device / process is ready
What is a file
a collection of data
What do file extensions do, what are some examples
- tell the computer what type of file it is
- .jpg, .mp3
what 6 parts of file management does the OS deal with
- organisation of data into a hierarchical structure
- naming
- deleting
- saving
- editing
- movement
What does the OS do with the hard disk
- chooses where to write data
- splits disc into storage sectors
- keeps track of free space
What type of software does the OS use to maintain the hard disk
utility software
What are single-user and multi-user OSs
single user allows one user at a time
multi user allows multiple users at the same time
What does the OS use user account control for
to grant specific access to data or resources on a computer system
What sort of anti-theft measures can be used on OSs
- password
- pin
- pattern
- fingerprint / retinal scanners
What are the three main types of utility software
- defragmentation software
- compression software
- encryption software
How do small gaps appear on a disk
When a file is edited , deleted or moved
Why does having data far apart in hard disks slow down reading / writing files
the read / write head has to move a lot further
What does defragmentation do
groups files next to each other so that all free space is collected in one place to maximise efficiency
why is defragmentation bad for SSDs
- no moving arm - data can be accessed just as easily no matter where the file is
- wastes the limited amount of read / write cycles
What does compression software do and what are its benefits
reduces size of files by removing data from them (temporary or permanent)
- take up less disc space and are quicker to download
What does encryption software do and why is it useful
- scrambles data so it can’t be read from a third-party
How does a computer decrypt a file
with a key and a set of instructions
