computer systems Flashcards
define the term hardware
the physical components of a computer system
define the term software
The instructions or programs that run on hardware
what is the logic gate for NOT
one input, triangle and circle to one output
what is the logic gate for OR
two inputs, bendy triangle to one output
what is the logic gate for AND
two inputs, rounded rectangle to one output
what is the logic gate for XOR
two inputs, bendy triangle with lining to one output
what represents the AND gate
.
what represents the OR gate
+
what represents the XOR gate
⊕
what represents the NOT gate
overbar
what is system software
Manages / controls computer hardware
what is application software
application software is software that performs end-user tasks.
what are the 5 main things that the operating system manages?
processors, memory, input/output, application, security
what type of architecture is the CPU in
von neumann architecture
what are the main components of the CPU
arithmetic logic unit
control unit
clock
register
bus.
what are the 3 factors that affect the performance of the CPU
clock speed
number of cores
cache size
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 (carried out). This may include reading/writing from/to main memory.
what is the aim of the fetch-execute cycle
The CPU continually reads instructions stored in main memory and executes them as required
what are the 4 different types memories in a computer
RAM
ROM
Cache
Register.
what is the full from of RAM
random access memory
what are the features of RAM
volatile(all data is lost when power is lost), faster to access, more expensive per unit,
what is the full form of ROM
read only memory
what are the features of ROM
non volatile, content cant be changed easily, stores small programs to boot/ start up the computer, fast but expensive,
what is the use of RAM (3 marks)
RAM is the volatile short-term memory that stores data whilst the computer is in use. The memory is lost when the computer is switched off.
what is the use of ROM and give an example (3 marks)
ROM is a non-volatile long-term memory that stores data that the computer needs to run, e.g. the operating system
what is the main memory
any form of memory hat is directly accessible by the CPU
what is secondary storage
Secondary storage is considered to be any non-volatile storage mechanism not directly accessible by the CPU.
what are the 3 types secondary storage
solid state, optical and magnetic
how do SSDs persistently store data?
through electrical logic gates and circuits
how does a HDDs get data from the memory
has a disc that spins very quickly. There is a read/write head that moves across the disc. The disc has tiny sectors which can be magnetised, they have magnetic polarity. This magnetic polarity can be read as 1s and 0s. Those 1s and 0s are transmitted to the computer from the drive. This data is stored permanently until its changed.
what are the disadvantages of a hard disc drive
the transfer rate is slower than solid state, can be wiped easily by a strong magnet, have moving parts which can wear down and break, it can get hot while moving very quickly, if you damage the hard drive all the data is lost, it requires more power to move (the disc uses more electricity), vulnerable to damage if there is slight movement
what are the advantages of hard disc drives
costs less than solid state(cost per gigabyte is lower)
what are the advantages of solid state drives
more moving parts so a lot less electronic consumption, can read and write data very quickly as it is reading from electronic circuits, very compact, very light, more robust (more likely to resist against damage), SD card uses the same technology, less heat is produced, use less power(reduced power use)
what are the disadvantages of solid state drives
more expensive (cost per gigabyte is higher), have a limited number of write operations to it (SSD endurance)
what does optical storage do to store
use lasers
how does optical storage get data from storage
The lasers can be red or blue which varies its wavelength which means it can read more as it is a minor position. The disc spins and while it spins a laser passes across the disc which shines onto the disc. The disc itself has pits and lands which reflects the light back and it measures the time from transmission to detection which it reads as binary 1s and 0s. To write things on, you have a laser that burns the pits and lands.
what are the disadvantages of optical storage
obsolete, you have to store them, not good environmentally as it has a lot of waste, more expensive for buyer, low life span, high distribution cost
what are the advantages of optical storage
data itself is easily portable, easy to make multiple copies
explain what cloud storage is
cloud storage is a secondary storage in a remote location, that you can access it via the internet.
what type of secondary storage does cloud storage use at what type of location
uses magnetic and/or solid state storage at a remote location.
what are the disadvantages of cloud storage
you can access your files from anywhere as long as you have internet connection and a device, the amount of electricity needed to power cloud storage. the data centre may get hacked so some else can access all the data,all the work can be collaborated on to share and distribute files. Since 2020, this has been used a lot more frequently to work from home. Having cloud storage means that you don’t need to have as much storage in your device. plus you can upgrade the storage in your device without upgrading your phone storage.
what are the advantages of cloud storage
big companies that use cloud storage drive the development of renewable energy,
if clock speed increases, what will the performance of the CPU be like?
increases num of instructions that can be processed per second so will be faster
if clock speed decreases, what will the performance of the CPU be like?
reduces heat, reduces num of instructions that can be processed per second so will be slower
if the number of cores are increased, what will the performance of the CPU be like?
more instructions can be processed at the same time so will be faster
if the cache size increased, what will the performance of the CPU be like?
less time the CPU is idle so will be faster
what is data compression
making data smaller for it to be easier to store
how is data compressed by huffman coding?
on a huffman tree, what numbers are on the left and right side of the branches?
0 on the left, 1 on the right
what is the full form of RLE
run length encoding
what does RLE do
takes a run of the same value but stores it in less
compress 000011100000111110000 using RLE
4 0 3 15 05 1 4 0
what is the Binary representation of RLE B15 W9
00001111 10001001
compress 0000011100000011 using RLE
5 0 3 1 6 0 2 1
what is true about code that is written using a low-level language?
the code is not translated using a compiler,
the code can directly manipulate registers
State two reasons why computers have more RAM than cache memory
- RAM is cheaper (per byte);
- Typically, the capacity of cache memory is not enough to store both data and
programs
How do interpreters work?
- translates / executes one like at a time
- needs interpreter to be present to run the code
- needs source code to be present
- needs to be translated each time it is executed
- stops execution when a error is reached
- executes code as it is being translated
how do compilers work?
- translates/ compiles the whole program in one go
- stand-alone program doesnt require compiler / source code on the computer to be run
- does not execute the code
- creates an executable file
What are advantages of high level language?
- quicker to write code and you can use multiple commands into one
- easier to debug and test high level
- other programmers understand high level making collaboration easier
- high level can have structured programming approaches like iterations etc
- easier for HUMANS to UNDERSTAND
what are the advantages of low level language?
- quicker to run as they don’t need to be converted from high level
- code takes up less storage
- interact with hardware director directly as they as designed to run on that hardware
What is source code
Original code, a set of instructions that are written in human readable language (high level)
