A Level ICT: Data Processing and Information — Revision Notes

Condensed for the final weeks. For the full explanation, use the Data Processing and Information study guide.

Data, information, knowledge

• Data — raw facts and figures with no context. 37, Smith, 2410.
• Information — data given context and meaning. “Patient Smith’s temperature is 37 °C.”
• Knowledge — information applied with understanding and rules. “37 °C is normal, so no action is required.”

The definition that scores is context. Data becomes information when meaning is attached to it, so the same figure can serve as data in one system and information in another.

Static and dynamic data

Static data does not change once recorded — a date of birth, a book’s ISBN. Dynamic data changes automatically as its source updates — a live share price, a sensor reading, a satellite navigation display.

Direct and indirect data sources

• Direct — collected for the specific purpose at hand: your own questionnaire, your own sensor readings.
• Indirect — collected for some other purpose and reused: census data, loyalty-card records used for marketing.

	Advantage	Disadvantage
Direct	Relevant, current, known accuracy, in the required format	Costly, slow to gather, may need a large sample
Indirect	Cheap, immediately available, often very large	May be out of date, wrong format, unknown bias, may include irrelevant data

The “may be in the wrong format” point for indirect data is frequently omitted and frequently worth a mark.

Quality of information

Information is only useful if it is:

• Accurate — free from error.
• Relevant — related to the purpose.
• Up to date — current enough for the decision.
• Complete — nothing essential missing.
• Presented appropriately — in a form the user can act on.
• Available on time — after the decision point it is worthless.

Poor-quality information leads to poor decisions — the practical reason validation and verification matter.

Encoding data

Coding data (M/F, L/M/S, country codes) has clear gains: less storage, faster entry, easier validation, and quicker searching and sorting.

But it also causes problems: coarse categories lose detail, codes must be learnt, and value judgements are distorted. Coding a garment colour as RD loses the difference between scarlet and burgundy — an example worth having ready.

Validation and verification

They are not the same thing, and this is the most commonly confused pair in the syllabus.

• Validation — an automatic computer check that data is reasonable and of the correct type. It cannot detect whether data is correct, only whether it is sensible.
• Verification — a check that data has been accurately transferred or copied, by double entry or visual proof-reading.

A valid but wrong date of birth passes every validation check ever written. Only verification against the source can catch it.

Validation check	Tests
Range	Value falls between limits
Type / character	Correct data type or characters
Length	Correct number of characters
Format / picture	Matches a pattern, e.g. two letters then four digits
Presence	A required field is not blank
Lookup	Value exists in a defined list
Check digit	Extra digit calculated from the others — used for ISBNs and barcodes

Processing methods

Method	Description	Best for
Batch	Data collected, processed later in a group, no user interaction	Payroll, billing, cheque clearing
Online / interactive	Processed as entered, user waits for a response	Booking systems, e-commerce
Real-time	Processed immediately, output affects the input source	Process control, autopilot, safety systems

Batch suits payroll because it is a large volume of similar transactions with no urgency, so processing can be scheduled overnight when the system is idle.

Real-time control differs from real-time transaction processing: in control systems the output feeds back to influence the next input, which is why a delay is unacceptable.

Databases

Flat file — a single table. Simple, but causes data redundancy (the same data stored repeatedly) and therefore inconsistency when one copy is updated and another is not.

Relational database — multiple linked tables. Reduces redundancy, improves integrity and security, and allows complex queries.

• Primary key — uniquely identifies each record.
• Foreign key — a primary key from another table, used to create the link.
• Referential integrity — prevents a record being deleted if other records still refer to it.

Normalisation organises data to eliminate redundancy. First normal form removes repeating groups; second removes partial dependencies; third removes transitive dependencies.

Exam traps

• Defining data and information without mentioning context.
• Confusing validation with verification.
• Claiming validation guarantees accuracy.
• Confusing direct with indirect data sources.
• Giving the advantages of coding without the loss of detail.
• Recommending batch processing where an immediate response is required.

Self-test

1. Distinguish data from information, and give the key word.
2. Distinguish direct from indirect data sources, with one drawback of each.
3. Explain the difference between validation and verification, and why validation is insufficient alone.
4. Name four validation checks and what each tests.
5. Why is batch processing suitable for payroll but not for airline booking?

Answers: 1. Data is raw facts without meaning; information is data with context applied. 2. Direct data is collected for the specific purpose but is costly and slow; indirect data was gathered for another purpose so it is cheap but may be out of date or in the wrong format. 3. Validation is an automatic check that data is reasonable; verification checks that data has been copied accurately. Validation alone is insufficient because incorrect data can still be entirely reasonable — a wrong but valid date of birth passes every check. 4. Range (value within limits), type (correct data type), length (correct number of characters), presence (field not blank) — also format, lookup and check digit. 5. Payroll is a high volume of similar transactions with no urgency, so it can be scheduled; booking requires an immediate response and confirmation, so it must be processed online.