Graphic file types

There are many different graphic file types which you can save an image using. SOme provide better graphic quality than others as well as differing in file size.

1. GIF – GIF stands for Graphic Interchange Format it is a standard file format used World Wide. IT is most commonly used for animations rather than coloured photos as it only is capable of representing 256 colours. Unlike JPEG it uses lossless compression techniques meaning no quality is lost. This image is only 24.3kb in size due to its inability to store a vast range of colours

rainbow GIF

PNG – PNG stands for Portable Network Graphics. It is similar to GIF as it shares the ability to support transparency. PNG was seen as a more developed version of GIF and can be compressed up to 25% more although it cannot store animation. This PNG image is 33.9 kb in size which is bigger than GIF but is far better in quality as it does not appear as grainy.

rainbow PNG

JPEG – JPEG stands for Joint Photographic Experts Group. This is used most commonly for photographs due to its ability to store around 16million colours. It does however use lossy compression meaning some quality is lost. The compression however makes changes in colour which the human eye cannot detect. This image is 26.4kb in size which is bigger in size than the GIF image but not as large as the PNG.

rainbow JPEG

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Revision Questions

1 ASCII vs UNICODE

a) An advantage of Unicode over ASCII is that it can store multiple lanuages where as ASCII only stores English characters. This is because ASCII only uses 7bits to represent each character compared to UNICODE which uses 16 bits.

b) A disadvantage of UNICODE over ASCII is that it takes up twice as much space when storing.

2) Representing negative numbers using two’s complement

72 represented as a positive number would look like this

01001000

When using twos complement to represent itas a negative it would look like this

10111000

nl

Increasing the width of the data bus enhances system performance as it means more data can be carried at once making tasks faster and so increases system performance.

4) Control lines

Two control lines are reset and clock.

reset-button       clock

5) Printer spooler

A printer spooler works by sending data from the computers backing storage to the printer in order to allow the user to carry out othertasks on the computer.

film_strip_clip_art_9205

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Vector graphics

Vector graphics are made up of lines and shapes rather than pixels like in a bitmap image.

Different attributes about these shapes are stored for example the colour, the coordinates, the line thickness or the fill colour.

coordinatesfill colour

colourline_thickness

An advantage of Vector graphics is that they have a much smaller file size than bitmap graphics.

This is because bitmap images have to store information about each individual pixel whereas vector graphics only store attributes about each shape or line.

For creating Vector graphics draw programmes such as draw plus are used. Whereas for creating a bitmap graphic paint programmes such as microsoft paint are used.

pencils            paintbrush

A disadvantage of Vector graphics however is that individual pixels cannot be changed. This means only the whole shape can be edited not just one small part of it.

Another advantage of vector graphics is that they are scaleable. This is an advantage as it means if the image needs to be enlarged then no quality is lost. When a bitmap image is enlarged then the image becomes more pixelated causing the image to appear blurry.

vector-vs-bitmap

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Audio technical terms

Clipping – This is when distortion of the sound is created because the output hardware is trying to represent a sound which is outwith its capability.

Stereo – This is when two tracks are used separately one is sent through one channel the other track is sent through the other channel. Therefore it gives an effect of live music.

Surround sound – This is when a sound is said to be all around the listener.

Fade – This is when audio gets gradually quieter before slowly disappearing

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Bitmapped graphics – Technical terms

Dithering – This is when patterns of dots are changed to make it look as if there are more colours than what they actually are. Dithering helps to make images with few colours appear less blocky however they can appear more grainy instead.

 

Anti- aliasing – This is a technique used to smooth out edges which appear jagged when seen on low quality output devices such as monitors.

Resampling – This is when the amount of pixels in an image is changed. Resampling can change both the resolution of the image and the size of the image depending on whether the amount of pixels is increased or decreased.

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The processor

The processor is the main part inside a computer as it links to many other parts. For example data is sent between the processor and backing storage so that when a computer is switched off no data is lost.   cpu

The Processor consists of many different parts such as Registers, ALU, Control Unit, Control Bus, Address Bus, Data Bus.All these different parts do different jobs within the processor.

Registers – These are used as temporary storage locations for data that is being processed. They are also used for when instructions are being carried out. They can also hold addresses of mmory locations to be accessed.

ALU – This is the arithmetic and Logic unit. This is where calculations are carried out and calcIt  out logical operations such as AND, NOT, OR are performed.

 

The control unit – This part of the processor is where  the fetching and decoding of instructions as well as the execution of the instuctions happens.

The control bus – This consists of several wires each having a separate function. There is a busread line, write line, interrupt, clock and reset. Each one of these does something different.

Address Bus –  The address bus carries information (on which memory location will be used to store the data) to the main memory. Each line only carries one piece of information at a time. The number of wires in this bus determines how many memory locations can be addressed the more wires the more locations.

Data Bus – The data bus carries between the processor and main memory. It is the only bus in which data is carried both ways. This stores data in memory locations and reads it from memory locations. The more wires this bus has the more data that can be carried at one time. The more data carried at once the faster the computer will be.

The fetch and execute cycle is used to execute a program. First of all any relevant data needed to run the programme must be FETCHED and stored in memory until it is required by the processor. It is then retrieved and each individual instruction is then EXECUTED one at a time.

fetchdecodeexecute

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Graphics

There are two different types of graphics bitmap graphics and vector graphics.

Bitmap graphics are made up of thousands of tiny dots called pixels. The number of dots determines the resolution. The more dots/ pixels the higher the resolution meaning the better quality of the image. The less dots/pixels the lower the resolution meaning it is worse quality. Images in which there are few pixels meaning each square can be seen are referred to as pixelated. Bitmap images are represented using binary. The number of bits used to store each colour in an image is known as the bit depth. Bitmap images have a fixed file area and can be edited to pixel level meaning individual colours can be changed. Bitmap images however Have a very large file size and so take up alot of space and making the image bigger causes some quality to be lost.

Vector graphics however are made up using shapes and lines and points. Unlike bitmap graphics however small colour changes cannot be made. It is stored by saving information about the attributes rather than using pixels. Vector graphics have a much samller file size and so do not take up as much space as bitmap graphics. Objects created can be resized and moved around.  Unlike bitmap graphics though the fine details cannot be edited and although they have a smaller file size as more shapes are added the file size increases.

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