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IT revision (Bitmaps (1) The type of images you use most often are called…
IT revision
Bitmaps
1) The type of images you use most often are called bitmap images- they're mainly used for photos. Bitmap images are made up of lots of tiny dots, called pixels
2) The colour of each pixel is represented by a binary code. The number of colours available in an image is related to the number of bit the code has.
5) You can make a greater range of shades and colours by increasing the number of bits for each pixel
3) Black and white images only use two colours, meaning they only need 1-bit to represent each pixel- o for white and black for 1
4) 2-bit images can be made up of four colours, Each pixel can be one of four binary values- 00, 01, 10, 11
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3) Most devices use a 24-bit colour depth, with 8 bits used to indicate the levels of re, green and blue needed for each pixel. It's estimated that the human eye can see around 10 million different colours, so a 24-bit colour depth should cover every colour that you could possibly see
4) The resolution is the density of pixels in an image by i.e how many pixels are within a certain area.
5) The higher the resolution the more pixels in a certain area and so better quality of image. E.g if an image has a resolution of 60 dpi, it means that a one-inch square contains a grid that is 60 pixels wide and 60 pixels high. So there are 60 x 60 = 3600 pixels in that square inch
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- Increasing the rate of resolution or the colour depth means that there are more bits in the image. This improves the image quality, but also increases the file size
Algorithams
Algoritham = a process or set of rules to be followed in calculations or other problem-solving operations, especially by a computer.
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- Algorithams can be wriiten as flow diagrams
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Pseudocode
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1) Pseudocode is not an actual programming language but it should follow a similar structure and read like one (roughly). The idea is that Pseudocode clearly shows an algorithm's steps without worrying about the finer details (syntax) of any particular programming language
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3) There are different ways to write Pseudocode- they are equally correct as long as the person reading the code can follow it and understand what you mean
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What are they?
- Operands = a term used to describe any object that is capable of being manipulated. For example, in "1 + 2" the "1" and "2" are the operands and the plus symbol is the operator.
- Opcodes = A single instruction that can be executed by the CPU. In machine language it is a binary or hexadecimal value such as 'B6' loaded into the instruction register. In assembly language mnemonic form an opcode is a command such as MOV or ADD
Compression
- Lossy Compression= Permanently removes some data
- Lossless Compression = No data lost, just less bits - works for less colour pixel picture
Networks
Advantages:
- Sharing devices such as printers saves money.
- Files can easily be shared between users.
- Security is good - users cannot see other users' files unlike on stand-alone machines.
- Data is easy to backup as all the data is stored on the file server.
Disadvantages:
- Purchasing the network cabling and file servers can be expensive.
- Managing a large network is complicated, requires training and a network manager usually needs to be employed.
- If the file server breaks down the files on the file server become inaccessible. Email might still work if it is on a separate server. The computers can still be used but are isolated.
- Viruses can spread to other computers throughout a computer network.
- There is a danger of hacking, particularly with wide area networks. Security procedures are needed to prevent such abuse, eg a firewall.
Sound Sampling
= Sound sampling is a way of converting real sounds into a form that a computer can store, and replay. Natural sound is in analogue form. Analogue means that something is continually changing, or to put another way, that it has no definite value.
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