Information Processing: Data, Representation and Data Quality
Information processing is the compulsory domain that asks how raw data is captured, represented and turned into information, and how its quality is protected. HKDSE questions often combine a definition with a calculation or a representation choice.
Data, information and processing
Data are raw, unprocessed facts or symbols; information is data that has been processed and given context so it can support a decision. A processing cycle includes capture, validation, classification, sorting, calculation, aggregation, storage, retrieval and presentation. The same data can yield different information depending on processing and context.
Digital representation
All data is stored as bits; 1 byte = 8 bits. Binary, denary and hexadecimal are different notations for the same values. Text is encoded with character sets: ASCII uses 7 bits (128 characters), extended ASCII 8 bits, and Unicode has a much larger repertoire for multilingual text and symbols. A bitmap image is a grid of pixels; its uncompressed size is width × height × colour depth ÷ 8 bytes. Vector graphics store geometric objects and scale without pixelation. Audio is digitised by sampling: size = sampling rate × bit depth × channels × seconds ÷ 8. Video adds frame rate.
Validation and verification
Validation checks whether input is acceptable: presence, range, type, format, list and check-digit checks. Verification checks whether data was copied or entered accurately: double entry and visual checking. Error detection during transmission uses parity bits and checksums. Validation cannot prove accuracy-a valid but wrong date of birth still passes.
Worked example
An uncompressed 1024 × 768 image uses 24-bit colour. Pixels = 1024 × 768 = 786,432. Bits = 786,432 × 24 = 18,874,368 bits. Bytes = 18,874,368 ÷ 8 = 2,359,296 B. In MiB = 2,359,296 ÷ 1,048,576 = 2.25 MiB. Reducing to 8-bit indexed colour gives 786,432 B = 0.75 MiB, one-third of the size, because colour depth falls from 24 to 8 bits per pixel.
Traps
Do not mix bits and bytes or decimal and binary prefixes. Real file sizes include headers, and compression changes the result. Do not confuse validation with verification, ASCII with Unicode, or bitmap with vector. Lossy compression permanently discards data; lossless does not.