You can print this page for a quick reference guide or you can use the tools below to create printable test sheets
4a: Recall that representations are used to store, communicate, and process information.
|communicate||sharing a message with someone else who might not have heard it before|
|data||unprocessed information (meaningless letters, numbers or symbols)|
|information||processed data (letters, numbers or symbols that have been organised and put into context)|
|process||understanding a message so that you can respond appropriately|
|representation||a way of describing a message so that it can be stored, communicated or processed|
|store||keeping a message safe so that it can be remembered for later|
4b: List examples of representations.
|alphabet||a way of representing messages using written symbols to represent words and sounds|
|ASCII||a way of representing messages using a different number for each letter of the alphabet and used by computers to send the numbers as binary digits|
|braille||a way of representing messages using bumps on a surface that blind people can read using their fingers|
|hieroglyphics||a way of representing messages using pictures to represent words|
|morse code||a way of representing messages using sequences of dots and dashes often transmitted as beeps over radio waves|
|semaphore||a way of representing messages using sequences of flags to send signals by line of sight|
4c: Provide examples of how different representations are appropriate for different tasks.
|alphabet||representation that is ideal for making notes in your school exercise books|
|ASCII||representation that is ideal for sending emails across the Internet|
|braille||representation that is ideal for enabling blind people to read by running their fingers over bumps|
|morse code||representation that is ideal for sending coded messages over radio waves across the ocean|
|semaphore||representation that is ideal for lifeguards on a beach to send a message via line of sight when it's too far to shout|
4d: Recall that characters can be represented as sequences of other symbols.
|character||a letter, numerical digit or punctuation mark|
|representation||a way of storing data so that it can be understood and shared|
|sequence||more than one character appearing in order|
|symbol||a way of representing something|
4e: Measure the size of a representation as the number of symbols that it contains.
|base||the number of different symbols available to use in each place in a sequence|
|base 10||a representation that has 10 different symbols (e.g. writing numbers in decimal with the numbers 0 - 9)|
|base 16||a representation that has 16 different symbols (e.g. describing colours in hexadecimal with 0-9 and A-F)|
|base 2||a representation that has two different symbols (e.g. binary with 0 and 1)|
|base 26||a representation that has 26 different symbols (e.g. writing messages using the letters A-Z)|
|base 64||a representation that has 64 different symbols (e.g. describing the contents of files using A-Z, a-z, 0-9 and some additional punctuation symbols)|
|message length||the number of symbols needed in a sequence to represent a message|
4f: Provide examples of how symbols are carried on physical media.
|CD||stores binary data on spinning discs covered in pits and lands which either absorb or reflect laser light|
|DVDs||stores binary data on spinning discs covered in pits and lands packed closely together which either absorb or reflect laser light|
|Ethernet||transmits binary data by sending and receiving electrical pulses down pairs of wires between two computers|
|Fibre Optic||transmits binary data by sending and receiving pulses of light inside a cable that reflects the signal so it can be detected at the other end|
|Hard Disk||stores binary data on spinning discs covered in tiny sectors which can be magnetised in one of two directions|
|Solid State Drive||stores binary data without any moving parts using electronic chips containing NAND gates and flash memory|
|WiFi||transmits binary data by sending and receiving radio pulses switched on and off at a very high frequency|
4g: Explain what binary digits (bits) are, in terms of familiar symbols, e.g. digits or letters.
|bit||one binary digit (either 0 or 1)|
|byte||a sequence of eight bits (from 00000000 to 11111111)|
|digit||a single character, letter or numerical symbol|
|nibble||a sequence of four bits (from 0000 to 1111)|
4h: Measure the size of a bit sequence as the number of binary digits that it contains.
|bit||an individual binary digit (0 or 1)|
|byte||a sequence of eight binary digits|
|gigabyte||a sequence of 1,000,000,000 bytes|
|kilobyte||a sequence of 1,000 bytes|
|megabyte||a sequence of 1,000,000 bytes|
|nibble||a sequence of four binary digits|
4i: Describe how natural numbers are represented as sequences of binary digits.
|bit||a single binary digit (0 or 1)|
|bit value||how much an individual bit is worth within a sequence of binary digits|
|byte||a sequence of 8 bits which can represent a value between 0 and 255|
|least significant bit||the bit with the lowest value (1) which can be found on the right, at the end of a sequence of bits|
|most significant bit||the bit with the highest value which can be found on the left, at the start of a sequence of bits|
|natural number||a whole number (without a decimal place)|
|nibble||a sequence of four bits which can represent a value between 0 and 15|
4j: Convert a decimal number to binary and vice versa.
|binary||a base 2 number system (using digits 0 and 1) where each digit is worth 2 times as much as the digit to its right|
|decimal||a base 10 number system (using digits 0-9) where each digit is worth 10 times as much as the digit to its right|
|denary||another name for decimal|
|unsigned||a number that can only greater than or equal to zero|
4k: Convert between different units of representation size.
|bit||1 individual binary digit (1 or 0)|
4l: Provide examples of how binary digits are physically represented in digital devices.
|bit||an individual binary digit|
|laser||light and sound emitting radiation (a focussed beam of light)|
|magnetic surface||covering of a spinning platter inside a hard disk drive which represents 1s and 0s by flipping the polarity of tiny magnetic areas|
|NAND gate||logic gate used in solid state storage devices to represent 1s and 0s|
|pits and lands||bumps on a CD, DVD or BLU-RAY disc which absorb or reflect laser light so it can be detected by a sensor as 1s and 0s|
|polarity||the direction of a magnetic or electric field|
|sensor||a device that can detect something and turn it into an electrical signal|
|transistor||digital switches used to process electrical signals which represent 1s and 0s|
4m: Recall that binary digits represent all information that is stored, transmitted, and processed by computers.
|ASCII||American Standard Code for Information Interchange (a way of converting each letter of the latin alphabet into a number so it can be represented in binary)|
|bitmap image||can be represented by binary digits by describing the colour of each using numbers and then converting each number into binary|
|numbers||can be represented in binary by converting from decimal to binary|
|sound||can be represented by binary digits by regularly sampling the amplitude (size) of a sound wave and converting each sample into binary|
|text||can be represented by binary digits by giving each letter a numerical value then converting that into binary|
|vector image||can be represented by binary digits by describing each shape and colour using numbers and then converting each number into binary|
|video||can be represented by binary digits by splitting it into frames of still images and describing each frame as a sequence of coloured pixels and sound|
4n: Describe how characters are represented as sequences of binary digits.
|ASCII||American Standard Code for Information Interchange (a way of using 7 bits to describe each letter in the Western European or American alphabet)|
|unicode||Standard that uses more than 7 bits to describe each letter in the alphabet so that special characters can be represented that can't be described using ASCII (like £ or letters with accents)|