pros and cons stuff + comparisons p1 Flashcards
magnetic storage
- reliable
- cost effective / provide high capacity storage at low costs
- not very portable due to having moving parts
solid state storage
- have no moving parts
- no moving parts means access to data is faster than for a magnetic HDD
- no moving parts means that power requiremenets are low and no noise or heat is generated
- SSDs are robust, lightweight and compact making them ideal for portable devices
- smaller capacity than magnetic Hdds
- cost per unit of storage is high
optical storage
- portable
- easily scratched
- low capacity per disc
client server network
Pros:
- easy file tracking, all stored centrally
- backup of files and update software easily
- servers reliable and always on
Cons:
- expensive to set up and maintain
- if the server goes down, all clients lose access
peer-peer network
Pros:
- easy to maintain without expertise
- no dependance on a server
Cons:
- updates and backups are complicated
- hard to track files - copying between devices creates duplicates
- data could be lost if one device fails
star topology
Pros:
- network unaffected
- easy to add more devices
- high performance
Cons:
- expensive for wired networks
- switch is a single point of failure
mesh topology
Pros:
- no single point of failure
- add devices without affecting performance
Cons:
- expensive for wired networks
- Hard to maintain lots of connections
character sets
Ascii:
- a 7 bit code to represent the english alphabet, numbers and some symbols.
- there are 128 chacracters available
- the codes for numbers and letters are ordered
Unicode:
- covers all major languages, including ones that use different alphabets, like Greek, Russian and Chinese
- uses multiple bytes for each character
- the first 128 characters in Unicode are the same as ASCII
secondary storage
secondary storage - non-volatile storage where programs and data are kept for later use.
Hard Disk Drives (HDDs):
- moving parts
- store data magnetically
- can be noisy
Solid State Drives (SSDs):
- no moving parts
- use flash memory for faster read/write times
- usually quiet/silent
Virtual Memory:
when a computer runs complex programs or multiple applications simultaneously, there may not be enough RAM to store all the neccesary data. In such cases, the computer uses a portion of secondary storage as an extension of RAM, known as virtual memory. IT moves data not currently needed by the CPU from RAM to secondary storage and retrieves it back when required. This process allows the computer to handle more data than the available Ram alone would permit
ram vs rom
RAM:
- holds the operating system. running applications, and associated data while the computer is on and in use
- Volatile - loses data when the power is turned off
- can be read and written to by the computer
- Temporary - only while the computer is powered on
- if insufficient RAM, uses virtual memory by moving data to and from secondary storage temporarily
ROM:
- stores the bootstrap leader/BIOS to start the computer from scratch
- Non volatile - retains the data even when the power is turned off
- Read Only: cannot be written to by the computer during normal operation
- permanent - data remains stored even when the computer is powered off
fetch-execute cycle
Fetch:
- memory address copied from the program counter to the MAR
- instruction copied from memory to the MDR
- program counter incremented to point to the next instruction
Decode:
- instruction in the mdr decoded by the control unit
- control unit prepares for next step by loading values into the MAR or MDR
Execute:
- decoded instruction carried out. Examples of instructions:
- load data from memory
- writes data to memory
- do calculation or logic operation (using the ALU)
registers
Memory Address Register (MAR):
- holds any memory address about to be used by the CPU. The address could point to data or an instruction
Memory Data Register (MDR):
- holds the actual data or instruction, either fetched from memory or waiting to be written to memory
Arithemtic Logic Unit (ALU):
- stores the result of calculations
Program Counter (PC):
- stores the address of the next instruction to be fetched from memory. (which sends the value to the mar) This counter increments by 1 in each FDE cycle.
cpu components
Control Unit:
controls the flow data in and out of the cpu. Manages the fetching decoding and executing of instructions.
Cache:
stores regularly used data for quick access. Low capacity and expensive.
Registers:
- temprarily hold small amounts of data. They’re extremely fast to read/write to
cpu performance
Number of cores:
each core processes data independently, so more cores means more instructions can be carried out per second. Some software is designed to take advantage of multicore processing.
Clock Speed:
the number of instructions a single processor core can carry out per second
Cache Size:
- a larger cpu cache gives the cpu faster access to more data
Types of Network
Local Area Network:
- lans cover small geographical areas at single sites
- can be wired or wireless
users on a lan can:
- access and share files on the network
- share hardware
- share an internet connection
WANS:
- geographically distanced
- more expensive to set up than LANs
-formed by connecting LANs together
factors that can affect network performance:
- bandwidth
- the number of users
- the transmission media being used
- error rate
network hardware
Network interface card (NIC):
- to allow a device to communicate with a network. Each NIC has a unique MAC address that allows it to be identified on the LAN
Transmission media:
wires or wireless radio waves that allow data transmission between devices
Wireless Access Points (WAPs):
a piece of hardware that connects to a network switch and allows wi-fi devices to connect to a network. The WAP is usually connected to a network switch. WAPs can also be used to extend the range of a wireless network.
Switches:
the piece of hardware that allows multiple devices to connect together to form a wired network. A switch stores the MAC address of every device connected to it in a table. When the switch receives a packet of data it looks at the destination address and forwards it on to the intended device
Routers:
protocols
network protocol - rules for how devices communicate, and how data is transmitted and organised across a network
ethernet - is the protocol used to connect devices in a wired LAN
wifi - is a set of protocols that defines how network devices can communicate wirelessly using radio waves. Wifi can transmit at the 2.4ghz frequency, whcih has a greater range but lower transmission speeds compared to transmission speeds at the higher frequency but a lower range
Bluetooth - is another form of wireless protocol, which can be used over short distances usin ultra-high frequency radio waves
Hypertext transfer protocol (HTTP) - defines how web browsers work
Hypertext transfer protocol secure (HTTPS) - is the same as HTTP but ‘s’ stands for secure, used for banking
File transfer protocol (FTP) - used to transfer computer files between a client and a server
Post office protocol (POP) - used to retrieve and download emails from an email server
Internet Message Access Protocol (IMAP) - alternative protocol for accessing email messages. However, the messages are read rather than downloaded
Simple Mail Transfer Protocol (SMTP) - used to send email to an email server
Transmission control protocol (TCP) - splits the data from applications into smaller data packets that can be sent across a network.
the cloud
Pros:
- access files from any device
- easy to increase storage space
- no need for expensive hardware and the staff to manage it
- host provides security and backups
- automatic updates
Cons:
- requires internet connection
- relies on host for security and backups
- stored data can be vulnerable to hackers
- unclear who has ownership of data
- expensive subscription fees
layers
- network communication is divided by functionality into layers
- each layer is self-contained. It serves the layer above it and depends on all layers below it
Benefits:
- developers can each focus on one area of the network
- layers can be changed without affecting others
- standards develop ensuring compatibility between different pieces of hardware and software
the internet
internet - a worldwide collection of computer networks
world wide web - a collection of websites hosted on web servers. accessed through the http protocol
url’s - addresses used to access web servers and resources on them
Domain name service (DNS):
- A server made of many domain name servers that store domain names and matching IP addresses
1) browser sends URL to DNS
2) DNS finds matching IP address and sends it back to browser
3) Browser requests web page from the web server at the IP address
4) web server processes the request and sends the web page back
operating system
Peripheral management and drivers:
- communicates with the internal hardware, and peripherals connected to the system, using drivers
- chooses correct drivers for connected hardware on startup
- installs drivers for new hardware and updates drivers automatically
Providing a user interface:
- allows users to interact with a computer. different interfaces are designed for different types of users. Graphical user interfaces and command line interfaces
Memory management and multitasking:
- moves application data to main memory when in use and removes it when it’s no longer needed
- allocates memory addresses so apps don’t overwrite or interfere with eachother
- divides CPU processing time between tasks to complete them efficiently
- uses memory buffers to store data until other components or processes are ready
File and disk management:
- organises files into a hierarchal structure of folders
- deals with naming, saving, moving, editing and deleting files and folders
- splits the hard disk into sectors and decides where files are written to
- maintains the hard disk with utility software
User management:
- controls which users, and how many users, can access the computer system
- grants users access to specific data and resources
- uses anti-theft measures to prevent access for other users - e.g. password protection.
utility software
utility software - software designed to help maintiain a computer system
Defragmentation:
over time, data on a hard drive becomes fragmented. parts of a file are saved to different areas of the disk where there is free space. This slows down the computer as more disk access is needed to read all of a file. Defragmentation software reorganises the files, putting all the free space together and all of the parts of the same file together.
Encryption software:
This is used to encode data so it cannot be understood if it is intercepted by unauthorised users. The encryption process uses an algorithm and key to transform the plaintext into cyphertext. The same software and key are needed to decrypt the data
Data Compression software:
- reduces the size of files by permanently or temporarily removing data from them
- compressed files take up less disk space and are quicker to upload and download
- compressed files need to be extracted before they can be used
Images
bitmap - a type of image made up of lots of tiny dots called pixels. The colour of each pixel is stored using a binary code
Image resolution - the number of pixels in a bitmap image. often given as width x height
Colour depth - the number of bits used to represent each pixel
total numver of colours = 2^n (where n = colour depth)
metadata - data about the data. e.g. height and width, colour depth, resolution, file format, date created.
sound
sampling - converting an analogue sound wave into digital data that can be read and stored by a computer.
sample rate - the number of samples taken per second. also called sampling frequency
Bit Depth - the number of bits available for each sample
