Computer Science - Unit 1

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What is a computer and what does it do?
A computer is an electrónic machine for processig data (general term for facts and figures, that can be procesed and stored by a computer). A computer proceses data - this means it turns data into useful information.
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What is there inside every computer and what does it do?
PROCESSOR - stores (stores data as electrical switches that can be on and off(on- conduct electricity. Off- carry electrical sígnal) and processes data)
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Binary
Binary is something that can be in exactly two states.(On or off). The data inside the computer is stored as binary ( a computer cant process or store data that isnt first in binary form). Binary = 1 and 0 as its easy to represent the on/off switches
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What are bits?
Binary numbers are made of the dígits 1 and 0. One single digit = bit. (Smallet piece of computer memory). 8 bits = 1 byte.
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What is the RAM and what does it do?
The RAM(random-access memory) is the área of the processor that stores data. Its sise depends on the bytes it can hold.
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Conversions:
1KB = 1000 bytes = 1/2 a page of text. 1MB = 1000000 bytes = 1/3 of a pic. 1GB = 1000000000bytes = 1/4 movie.
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What does processing data mean?
The computer processor makes changes to the data in the RAM. This process will be very quick. If there isnt enjugó room in the RAM outside storage can be used.
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What is a register?
Data that is ready to be procesed is copies into a smaller área of memory - register. The more register the quicker the computer works.
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What is th denary system?
Also known as base 10- every number can be represented usin 10 digits. The value of the digit depends on its position. Each time we move it to the left it has a value that is 10 times bigger. In binary the value is increased by 2.
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What is hexidecimal?
Number system that uses 16 different digits (base 16). The digits are the number 0-9 and the letters A-F. Each coloumn is worth 16 times more than the previous.
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What are the disadvantages of Binary?
· It is hard to read and understand. · It is easy to make mistakes. ·It is hard to then spot and fix the mistake. ·It takes up a lot of space. ·Hard to convert to denary.
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What are the advantages of hexidecimal?
· Easy to turn into binary. ·Much easier to read, write and understand. ·Takes up less space. ·Easier to debug.
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How is data turned into binary numbers?
The computer uses different coding systems. When a person uses binary it turns it into hexadecimal.
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What is hexadecimal used for?
RAM - stores data as bits and the addresses of the data as bits. Everything about the RAM is store as bits , which is converted into hexidecimal to makeup make it easier.
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What is hexidecimal used for?
COLOURS - Colour information is store in "24-bit colour". It is made of 3 bytes of data. One byte to store red / blue and green. By mixing various amounts of each colour you can get many combinations which can be written as hexidecimal.
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What is hexidecimal used for?
MACHINE CODE( a number code system that turns software - binary.) Programers usually turn these numbers into hexidecimal. Assembly language can be also used to represent machine code.
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Number values
1 byte can hold all numbers from 0- 255. By joining several bytes the computer can store bigger integers. Fraction = floating point number. 1 extra byte is used to store the position of the point.
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What is ASCII?
ASCII is a basic character code that is used to represent each character on a keyboard.
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What are formats?
The different way for storing digital data. You can know the format by looking at the file name. The file extension tells you what type of data is stored.Eg, .txt- text stored as ASCII, .doc- text + document formatting, exe.- instructions.
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What are pictures inside a computer?
Picture/ images are held in digital format. A computer is made o¡up of millions of dots - pixels. It represents one point of light on a screen or a dot of ink on a page. Different types of graphic software are used to make images.
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What is bitmap graphic?
Stores the position and colour of every pixel that makes up an image. A bitmap file is normally very large. It is a good way to store photographic and realistic images. Bitmap files have a high resolution. (.bmp)
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What is vector graphics?
Shapes constructed from lines. Mathematical formula tells the computer how to draw shapes and lines. A vector file is smaller, is good for images made of simple lines. (.svg)
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What is pixelation?
When th size of an image is increased and all the dots get bigger, the image looks distorted.
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What is colour depth?
The number of colours that can be used in an image.
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What are the different ways of storing the colour of each pixel?
·Monochrome- each pixel is either black or white, only uses 1 bit. ·16- colour- each pixel is half a byte. ·256- colour - each pixel is one byte.
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What are the different audio formats?
·WAV: stores music very accurately, high quality. But the files are very big (radio broadcasters). ·MP3: uses much less storage space, but of lower quality (own devices).·MIDI: stores instructions to send to an audio synthesiser to generate the notes
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What is MP4?
Is a container normally used to store video files. It can be used by a wide range of devices, as it doesn't use standard method to format the content it holds, but it can only hold pre-recorded content.
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What is bit-rate?
The number of bits used to store 1 second of sound.
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What does bit-rate depend on?
·Sample rate: number of times the sound changes / second. ·Number of channels. ·Bit depth (range of sound frequencies) For vídeos it depends on all of this + the quality of the image.
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How do you calculate the storage size?
By multiplying sample rate x number of channels x bit depth.
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Why is compression important?
Compressed files- don't use a lot of memory, don't slow the computer, don't take up a lot of storage space and aren't slow to send..
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What is lossy compression?
Produces a big reduction of the file size and data quality is reduced.
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What is loseless compression?
Reduces the file size but there isn't a reduction of quality.
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How can you compress an image file?
·Using fewer pixels. ·Using different bytes to store the colour. ·Remove repetition. ·Using JPEG(a lossy compression)
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How can you compress an audio file?
·Using fewer channels. ·Lower sample rate. ·Reduce bit depth. ·Use MP3
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How can you compress a video file?
Reducing the same things as an audio file + the image quality.
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What does debug mean?
To find errors in data
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What is Unicode?
It is an international code used to represent text character. Can store moe characters than ASCII.
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What does digital mean?
Something that has a precise value and can be represented as a number
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Other cards in this set

Card 2

Front

What is there inside every computer and what does it do?

Back

PROCESSOR - stores (stores data as electrical switches that can be on and off(on- conduct electricity. Off- carry electrical sígnal) and processes data)

Card 3

Front

Binary

Back

Preview of the front of card 3

Card 4

Front

What are bits?

Back

Preview of the front of card 4

Card 5

Front

What is the RAM and what does it do?

Back

Preview of the front of card 5
View more cards

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