GCSE Digital Technology CCEA

Representing Data

Representing Data

Binary System

• A binary system is composed of only two characters: 0 and 1.
• It's a base 2 system, opposed to our usual base 10 numeric system.
• In digital context, 1 represents 'on' and 0 represents 'off'.
• Each binary digit is known as a bit.
• 8 bits make up a byte.

Data Formats

• Text is encoded using character sets like ASCII and Unicode.
• Graphics are represented pixel by pixel, each pixel has a binary code that decides its colour.
• Sound is turned into data via sampling, where a snapshot of sound wave amplitude is taken at frequent intervals.
• Video is stored as individual frames, which are essentially still images, along with synchronised sound data.

Data Compression

• Data compression is about reducing the size of data files.
• Lossless compression allows the original data to be perfectly reconstructed from the compressed data. It is used with text and data where we cannot afford to lose any information.
• Lossy Compression loses some data during compression. It is typically used for video, audio and images, where a small loss of quality is often not noticeable.

Data Units

• The most basic unit in computing is bit (b).
• A byte (B) is 8 bits.
• Larger data are represented in kilobytes (KB), megabytes (MB), gigabytes (GB), and terabytes (TB).

Hexadecimal System

• Hexadecimal system, often used in computing, is a base 16 system.
• It uses ten digits from 0 to 9, and six more with letters from A to F.
• Hexadecimal coding is often used to represent binary code because one hexadecimal digit can represent four binary digits.

Number Systems Conversions

• Converting from binary to decimal involves adding the values of each digit where the binary number is 1.
• To convert decimal to binary, repeatedly divide by 2 and note the remainder. The binary number will be the remainders in reverse order.
• Hexadecimal to binary involves swapping each hexadecimal digit for its corresponding four digit binary number.
• To convert binary to hexadecimal, group the binary digits into sets of four, starting from the right, and swap these for the corresponding hexadecimal digit.