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OCR Computer Science Xichao > mock paper 1 > Flashcards

mock paper 1 Flashcards

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1
Q

areas required

A
  • number system
  • compression
  • network protocol
  • system architecture
  • virtual memory
  • software
  • ip address
  • DNS
  • ethics
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2
Q

brief summary of compression

A
  • 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
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3
Q

why do we need to compress files

and its uses

A

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
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4
Q

lossy compression pro and cons

And common file types

A

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)
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5
Q

lossless compression pro and cons

A

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)
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6
Q

what is a network protocol

A

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

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7
Q

MAC address communication on the same network

A
  • 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
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8
Q

IP address between different networks

A

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

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9
Q

TCP/ip

A

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.
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10
Q

FTP - file transfer protocol

A

used to access, edit and move files on other devices on the network

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11
Q

SMTP - simple mail transfer protocol

A

used to send emails between servers

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12
Q

pop3 - post office protocol

A

retrieve email from a server,
when the user download the email,
the server deletes it

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13
Q

IMAP - internet message access protocol

A

retrieve email from a server.

you download a copy and the server will only delete it if you delete it

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14
Q

SMTP - simple mail transfer protocol

A

send emails,

transfer emails between servers

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15
Q

what are the layers of a network protocol and its advantages

A

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
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16
Q

Purpose of computer

A

take data, process it, output it

Created to help process data and complete tasks more efficiently than humans

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17
Q

embed system

A

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

18
Q

what is the control unit

A

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

19
Q

what is the arithmetic logic unit?

A

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

20
Q

what is cache

A

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…

21
Q

The purpose of the CPU -fetch decode execute cycle

A

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

22
Q

Virtual memory

A

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

23
Q

Von Neumann architecture

A

a system where the CPU runs instructions stored in memory

programs consist of instructions and data which are stored in memory address

24
Q

What register is in the arithmetic and logic unit

A

accumulator

stores intermediate result of calculation in the ALU

25
Q

registers

A

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

26
Q

MAR

A

holds the memorise address about to be used by memory.

the address might point to data or instruction

27
Q

MDR

A

holds the actual data or instruction. this may be fetched from memory or waiting to be written to memory

28
Q

PC

A

holds the memory address of the instruction for each cycle

29
Q

Accumulator

A

store the intermediate result of calculations in the ALU

30
Q

operating system

A

user interface

memory management and multitasking

peripheral management and drivers

user management

file management

31
Q

Device Drivers

A
  • 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
32
Q

defragmentation

A

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

33
Q

Compression

A

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

34
Q

encryption

A

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

35
Q

functions of an OS

A
  • 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
36
Q

user interface

A

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
37
Q

memory management and multitasking

A
  • 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
38
Q

user management

A
  • single user or multiple users
39
Q

file/disk management

A
  • 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
40
Q

DNS - domain name server

A

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.

41
Q

ethics

A

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

OCR Computer Science Xichao (6 decks)

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