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TOPIC 2 - DATA, ASCII- american standard code for information interchange,…
TOPIC 2 - DATA
Binary a number system made up od 0 and 1 used by computers to store and represent data such as numbers,sounds, and graphics
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Bitmap images computers represnt imgaes in binary- images are broken down using a grid-each square in the grid is known as a pixel
Sounds in binary
Amplitude - the height of the sound wave at the time it was sampled. the higher the samplitude the louder the sound
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Binary maths
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MULTIPLICATION -BINARY SHIFT moves the digits to the left and fill the gaps after the shift with 0. move 1 place for X2, 2 places for X4 etc
DIVISION moves the digits to the right and full the gaps after the sift with 0. move 1 place for X2, 2 places for X4 etc
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TOPIC 3 - COMPUTERS
RAM-RANDOM ACCESS MEMORY . Volatile memory - data is lost when the computer is turned of
. called random acccess becwause data can be directlyy written to or read from any location
. used to hold data and instructions that are currently in use
. The more RAM a computer has , the more dta it can hold simutaneously
VONN NEUMAN ARCHITECTURE
KEY ELEMENTS: - data and instrcutions are stored in binary
- data and instrcutions are stored together in RAM
- Instrcutions are fetched from the Ram one at a time in order
- The CPU decodes and executes an instrcution, before fetching the next instruction
- the cycle continues unril no more instrcutions are avalilable
A cpu using vonn neumann architecture have five special registers :
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FETCH Each instruction is fetched from memory (in order), and put into the appropriate registers.
the process of converting encoded data back into its original, readable format
Programming languages
LOW LEVEL -very close to computer language , hard for humans to understand
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Assembly lnaguage also nown as assembly code, uses mnemonics (abbreviations) and is easier for humans to understand and program but is still abit diffuclt
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tcp/ip model
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Transport layer breaks down the message into packets which all are assigned packet numbers
-recipient uses the packet numbers to asseble the packets in correct order and to see if there are any missing packets
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compression
lossy compression: -some data is removed, reducing the amount of data and the size of the file
- there is a balance to be struck between reducing file sizes and mantianing quality
-images can be compressed by reducing colour depth
-audio files can be compressed by reducing the bit depth of the samples
-lossy standards include:
. JPEG file format for video
. MPEG file format for video and audio
.MP3 file formatr for audio
lossless compression -files are reduced in size without the loss of data
-lossless compression results in a smaller reduction in file soze than lossy compression
-lossless compressiojn gives a better file wuality than lossy compression
-lossless standards include
.PDF file format for documents
.GIF file formats for images
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Network security
access control determines what files,software and systems users have acccess to
-users restricted to access only the facilities they need for their jobs
-restrictions limit the actions a user can take,reducing the potential of threats
firewalls a tool which monitors traffic going in and out of the network
- either allows or blocks it
-decision is based on rules(known as the firewall policy)
- can be hardware based or software based
-hardware firewaslls are expensive but more effective and powerful
Physical security restricting the physical access to important systems and parts of the network
-important things such as :
-servers should be kept in a locked secure room
-access only available to autjorised people
this is because:
-someone could remove or access the hard disks containing private information or damge the equipment
NETWORK TOPOLOGIES
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bus network alll devices are connected to a single cable called the bus
-a terminator is ath each end of the cable
advantages:
- easy to install extra devices
-cheap to install as it doesnt require much cables
disadvantages
- if the cable fails or is damaged the whole network will fail
-performance becomes slower of additional devices connected due to data collisions
- each data recieved all data - security risk
star network all nodes are connected to one or more centeral switches, often used wiith wireless networks.
advantages
- every device has its own connection so failure of one node will not affect the other
-new devices can be added by simply connecting them with the switch
- usually have higher performance as a mesage is passed only to itsb intended recipeient.
disadvantages:
- if the switch fails it takes out the whole network
-requires alot of cables so it can be expensive
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TYPES OF NETWORKS
TOPIC 4 - NETWORKS
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WAN: wide area networks-covers a wide geographical area
-used by organisations with several different sites such as banks or universities
-allows all the sites to communicate and share dta
uses national or international long distance media
LAN- local area network -confined to a single location
-owned and mantianed by a single organisation
-used by organsiations such as schools and small businesses
-connected by cables or wireless
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colour depth
the more colours an image needs, the more bits per pixel are used
the greater the colour depth, the larger the image file will be
one bit per pixel (0or1)- two possible colours
two bits per pixel (00 or 11)- four possible colours
three bits per pixel (000 or 111) - eight possible colours
File size
The size of an image can be calculated using the formula:
height in pixels x width in pixels x colour depth per pixel
- Software and files can be shared -Hardwares such as printers can be shared
-users can communicate via email or chat etc
-centralised maintence and updates
centralised security
-user monitoring
-different userscan be given different access rights or permisions
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it is important to identify and fix vulnerabilities before they can be taken adavnatage of by hackers
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EXECUTE to carry out or run a program, command, or instruction
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high spped internal connections -used to send control signals and data between the processor and other components
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The internet - a vast wan covering rhe entire world
-an internet service provider (ISP) provides access to the internet
-routers provide an interface between the internet and the custmers via the ISP
-larger,more powerful routers connect the different components of the internet
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-alows the creation of a general idea of how to solve the problem
-provides focus on what actually needs to be done
-provides a simple view of the problem
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