HT4: Binary Data

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4a: Recall that representations are used to store, communicate, and process information.

Keyword | Definition |
---|---|

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.

Keyword | Definition |
---|---|

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.

Keyword | Definition |
---|---|

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.

Keyword | Definition |
---|---|

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.

Keyword | Definition |
---|---|

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.

Keyword | Definition |
---|---|

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.

Keyword | Definition |
---|---|

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.

Keyword | Definition |
---|---|

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.

Keyword | Definition |
---|---|

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.

Keyword | Definition |
---|---|

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.

Keyword | Definition |
---|---|

bit | 1 individual binary digit (1 or 0) |

byte | 8 bits |

gibibyte | 1,024 mebibytes |

gigabyte | 1,000 megabytes |

kibibyte | 1,024 bytes |

kilobyte | 1,000 bytes |

mebibyte | 1,024 kibibytes |

megabyte | 1,000 kilobytes |

nibble | 4 bits |

tebibyte | 1,024 gibibytes |

terabyte | 1,000 megabytes |

4l: Provide examples of how binary digits are physically represented in digital devices.

Keyword | Definition |
---|---|

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.

Keyword | Definition |
---|---|

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.

Keyword | Definition |
---|---|

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) |