mock paper 1 Flashcards
areas required
- number system
- compression
- network protocol
- system architecture
- virtual memory
- software
- ip address
- DNS
- ethics
brief summary of compression
- reduce the file size by permanently or temporarily removing data from them
- take up less disk space and are quicker to download
- standard file formats include .zip and .rar
- compressed files need to be extracted before they can be used
why do we need to compress files
and its uses
data compression makes file smaller while trying to make the compressed as true as possible
- smaller files take up less storage
- makes streaming and downloading faster as they take up less bandwidth
- allow webpage to load faster
- attach big files on email
lossy compression pro and cons
And common file types
permanently removing data
pro:
- greatly reduced size
- take up less bandwidth
- commonly used (lots of files can read lossy files)
con:
- lose data - can not be reverted
- can’t be used on text files
- worse quality than original although often unnoticeable
common file types:
- MP3 (audio)
- AAC (audio)
- JPEG (image)
lossless compression pro and cons
temporarily removing data and then restore it to its original state
pro:
- no reduction in quality
- can be depressed to original
- can be used on text and software files
con:
only slight reduction eg
common file types :
- TIFF (image)
- PNG (image)
- FLAC (audio)
what is a network protocol
rules for how devices communicate and how data is transmitted across a network
network standard is a set of agreed requirement for hardware and software
standards are important as they allow manufacturers to create products compatible with other manufacturerss
MAC address communication on the same network
- every device needs a unique identifier
- MAC addresses is assigned to all network-enabled devices by the manufacturer
- unique and cannot be changed
- 48/64 bit binary numbers and to make easier they are normally converted to hex
- ethernet protocol on LANs and switches read the mac address and use them to direct data to the correct device
IP address between different networks
IP are used when sending data between TCP/IP networks eg over the internet
IP are assigned manually or automatically before device can access the network
IPv4(32 bits) IPv6(128 bits)
ipv6 split into 16bits
ipv4 split into 8 bits
TCP/ip
TCP/IP is the protocol that dictates how data is sent between networks. It is made up of two protocols
Transmission Control Protocol (TCP) - rules for how to connect to the network.
- splitting up packets and reassembling them
- checking data is correctly sent and delivered
Internet Protocol(IP) -directing packets to their destination across the network.
FTP - file transfer protocol
used to access, edit and move files on other devices on the network
SMTP - simple mail transfer protocol
used to send emails between servers
pop3 - post office protocol
retrieve email from a server,
when the user download the email,
the server deletes it
IMAP - internet message access protocol
retrieve email from a server.
you download a copy and the server will only delete it if you delete it
SMTP - simple mail transfer protocol
send emails,
transfer emails between servers
what are the layers of a network protocol and its advantages
a layer is a group of protocols with similar functions
- each layer is self-contained
- serves the layer above it
- data can only be passed between adjacent layers eg 1 -> 2, 1 3.
advantages:
- breaks network communication into manageable pieces, which helps developers to focus on only one area
- as they are self-contained, they can be changed without other layers affected
- having standards for each layer forces companies to make compatible universal hardware
Purpose of computer
take data, process it, output it
Created to help process data and complete tasks more efficiently than humans
embed system
computers built onto other devices, a system that is part of a larger system
dedicated to a single task, easier to design, cheaper to produce, more efficient at doing their task than a general-purpose computer
what is the control unit
overall control of the CPU, manage fetching decoding and executing of program instructions by following the f-e cycle
controls the flow of data inside the CPU and outside the CPU
what is the arithmetic logic unit?
does all the calculations
perform simple addition subtraction and compares the size of numbers and can do multiplication division using repeated addition…
perform logic operations and binary shifts
contains accumulator register
what is cache
very fast memory in the CPU
slower than register faster than ram
stores regularly used data so CPU can access it quickly next time it is used, CPU checks cache first before checking the ram
they have low capacity and are more expensive compared to ram and secondary storage
different levels of cache memory l1 is the quickest and has the lowest capacity. l3 slower more capacity…
The purpose of the CPU -fetch decode execute cycle
fetch instruction
copy memory address from pc to mar
copy instruction stored in mar address to MDR
increment pc
decode instruction
instruction in MDR is decoded by CU, CU then prepare for the next step
execution Instruction
the instruction is performed.
this could be load data from the memory, write data to memory, calculation or logic operation (using the ALU) change address in PC, or halt the program
repeat
Virtual memory
Secondary storage used as RAM
when ram is filled with data it uses secondary storage
it moves data that has not recently being used into secondary storage
used when using memory intensive apps or too many apps opened at once
it slow as data need to be moved back to RAM to be read again by cpu
slow to respond when switching applications
Von Neumann architecture
a system where the CPU runs instructions stored in memory
programs consist of instructions and data which are stored in memory address
What register is in the arithmetic and logic unit
accumulator
stores intermediate result of calculation in the ALU
registers
memory address registers MAR
holds memory address about to be used by the CPU. the address might point to data or a CPU instruction
memory data register MDR
holds the actual data or instruction
MAR
holds the memorise address about to be used by memory.
the address might point to data or instruction
MDR
holds the actual data or instruction. this may be fetched from memory or waiting to be written to memory
PC
holds the memory address of the instruction for each cycle
Accumulator
store the intermediate result of calculations in the ALU
operating system
user interface
memory management and multitasking
peripheral management and drivers
user management
file management
Device Drivers
- a ‘translator’ for signals between OS and hardware
- os choose correct device drivers for the hardware it detects, new hardware connected will require system to install a new matching driver
- device manufacturer may release new drivers to fix bugs, add feature, or improve performance
defragmentation
In HDDs
when files are moved, deleted, change size small gaps appear on disk,
OS split files into smaller blocks to fill up the gaps,
over time file becomes more and more fragmented this makes reading and writing files slower, as the read/write head need to move back and forth the disk
defragmentation software reorganises data put fragmented files together. It also moves files to collect all the free spaces to prevent further fragmentation
Compression
reduce size of file by permanently or temporarily removing data from them,
compressed files take up less disk space and are quicker to download
format includes .zip and .rar
they need to be extracted before use
encryption
protects data
cypher (scrabbles) data to prevent third party from accessing it.
main benefit is that intercepted or stolen data is still secure as only the intended readers can unscramble them
to decrypt a special key is required; computer uses the key to revert it back to its original form
functions of an OS
- communicate with internal and external devices via device driver
- provide user interface
- provide platform for different applications to run
- manage security
- Multi-tasking by controlling memory resources
- file management, disk management
user interface
GUI - designed to be easy for everyday user by making them visual
- optimised for specific input methods,
- WIMP based (windows, icons, menus, pointers)
- IOS android created for touch screen devices
CLI - text based
- less resource heavy
- far more efficient and powerful
- can be used to automate process using scripts
memory management and multitasking
- effectively managing memory and CPU process time
- when the application is opened the os moves the necessary parts of the applications to memory, followed by additional parts when they are required.
- to run multiple applications the OS makes sure applications don’t overwrite or interfere with each other
- one application at a time, other processed must wait, OS divides CPU time between open applications and may prioritise certain processes into the most efficient order
- manage the flow of data by using memory buffers. devices and process will sen receive and process data at different speeds - temporary memory buffers store the data until the component device or process is ready
user management
- single user or multiple users
file/disk management
- stores data, file extensions tell the computer what type of file it is
- file management, organised data into a usable hierarchical structure and also deals with
naming, saving, movements, editing, deleting - hard disk splits the physical disk into storage sectors, decides which sector to write data to, and keep track of free space on the disk.
- when required os manage movement of data from and to virtual memory
- OS help manage the flow of data in the system by sing memory buffers. Different types of computer components, devices will send receive and process data at different speeds
temporary memory buffers store the data until the component, device or process is ready
DNS - domain name server
translate website’s domain name into IP address - this means you don’t need to remember IP address to access websites - you can use domain name instead
these services uses a network of domain name servers which stores IP address and domain names.
ethics
privacy
censorship and surveillance
social wellbeing - peer pressure, bully, face to face interactions can be neglected
smartphone makes it easy for people’s work to intrude different areas of their life
health problem
culture problem
selfies - makes people attention seeking and self obsessed
viral -news spread quickly, can be used for promotional campaigns
social media and blogging - gives voice to everyone, fake news
