Fundamentals Of Data Representation

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Integer

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Any whole positive or negative number including zero.

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Rational Number

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Any number that can be expressed as a fraction or ratio of integers.

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Irrational Number

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A number that cannot be represented by fractions or ratio.

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Real Number

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Any positive or negative number with or without a fractional part.

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Natural Numbers

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A positive whole number including zero.

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Bit

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A single binary digit from a binary number - 1 or 0.

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Byte

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8 bits.

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Nibble

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4 bits.

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Unsigned Binary

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Binary that represents positive numbers only.

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Two's Complement

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A method of working with signed binary values.

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Signed Binary

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Binary with a positive or negative sign.

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Character Code

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A binary representation of a particular letter, number of special character.

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American Standard Code for Information Interchange (ASCII)

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A standard binary coding system for characters and numbers.

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Unicode

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A standard binary coding system that has superseded ASCII.

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Parity Bit

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A method of checking binary codes by counting the number of 0's and 1's in the code.

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Majority Voting

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A method of checking for errors by producing the same data several times and checking it is the same each time.

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Check Digit

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A digit added to the end of binary data to check the data is accurate.

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Bit Mapped Graphic

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An image made up of individual pixels.

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Pixel

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An individual picture element.

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Resolution

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Width x height or pixels per inch.

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Colour Depth

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The number of bits allocated to represent the colour of a pixel in a bit mapped graphic.

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Vector Graphic

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An image made up of objects and coordinates.

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Compression

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The process of reducing the number of bits required to represent data.

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Run Length Encoding (RLE)

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A method of compressing data by eliminating repeated data.

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Encryption

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The process of turning plaintext into scrambled ciphertext, which can only be understood if it is decrypted.

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Decryption

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The process of deciphering encrypted data of messages.

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Plaintext

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Data in human readable form. Also known as unencrypted data.

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Ciphertext

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Encrypted data.

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Caesar Cipher

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A substitution cipher where one character of plaintext is substituted for another which becomes the ciphertext.

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Vernam Cipher

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A method of encryption that uses a one-time pad (key) to create ciphertext that is mathematically impossible to decrypt without a key.

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Key

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Used to encrypt and decrypt data.

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One-time pad

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A key that can only be used once to encrypt and decrypt a message and is then discarded.

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Metadata

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Data about data which is stored in the same file as the image data.

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Nyquist Theorem

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Sampling rate is at least twice the highest frequency.

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MIDI

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Musical Information Digital Interface, a way or representing the sounds made by an instrument.

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Synthesise Sound

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Manufactured sound, sound produced by a computer.

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Analogue Signal

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Continuous signal, various frequencies.

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Digital Signal

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Discrete signal, uses whole numbers, binary values (1's or 0's).