CARA'S TIPSData hierarchy, file organisation, access, file security
JAMBWAECNECO
What the syllabus asks
JAMB: Section D Managing computer files (1 Concept of computer files: file, record, field, data item; data types numeric, alphabetic, alphanumeric; data item–field–record–file–database; file organisation serial, sequential, indexed, random; access methods; master, transaction and reference files; criteria for classifying files; 2 Handling computer files: create, delete, retrieve, insert, copy, view,…
WAEC: Managing computer files (concept; handling; effects of file insecurity; causes of data loss; methods of security; computer vs manual files, advantages and disadvantages)
NECO: Managing computer files (concept; handling; effects of file insecurity; causes of data loss; methods of security; computer vs manual files, advantages and disadvantages)
What you will learn
- Define data processing and describe the steps in information processing.
- Define data item, field, record, file and database and show their relationship.
- Identify numeric, alphabetic and alphanumeric data.
- Describe serial, sequential, indexed and random file organisation and compare them.
- Explain serial, sequential and random access.
- Classify files as master, transaction and reference files and state the criteria for classifying files.
- Describe basic file operations.
- State the effects of file insecurity and the causes of data loss.
- Describe methods of securing data and maintaining integrity, including validation and verification.
- Compare computer files with manual files.
Key points
- Data processing turns data into information: collect, prepare, input, process, store, output, disseminate.
- Batch processing groups transactions; real-time processes each immediately.
- Hierarchy: bit → byte → data item → field → record → file → database.
- A key field uniquely identifies each record.
- Data types: numeric, alphabetic, alphanumeric (plus date, Boolean, currency in software).
- Serial: arrival order. Sequential: key order. Indexed sequential: key order plus index. Random: hashed address.
- Access: serial/sequential (tape, high hit rate) vs random/direct (disk, quick single look-ups).
- Master file: permanent main data. Transaction file: changes. Reference file: look-up data.
- Criteria: content, organisation, medium, purpose, date, size.
- Operations: create, open, retrieve, insert, update, delete, copy, sort, merge, close.
- Effects of insecurity: loss, corruption, unreliable data.
- Causes of loss: overwriting, deletion, hardware failure, viruses, theft, arson, disasters, power problems.
- Security: backup (GFS), antivirus, passwords, biometrics, encryption, labelling, CCTV, locks, extinguishers, smoke alarms, UPS.
- Validation checks data is sensible; verification checks it was copied correctly.
- Computer files: fast, compact, secure, shareable; but costly, power-dependent and exposed to viruses.
Start here: Data processing and its steps
Data processing (also called information processing) is the series of actions that turn raw data into useful information. It can be manual (pen, paper and files), mechanical (typewriters, calculators) or electronic (computers). Electronic data processing (EDP) is fastest and most accurate for large volumes.
Steps in information processing (WAEC Data Processing)
- Data collection (origination): gathering raw data from source documents, forms, sensors or interviews, e.g. collecting continuous-assessment scores from subject teachers.
- Data preparation: checking, coding and organising data so it is ready for entry; removing obvious errors.
- Data input: entering the data into the computer by keyboard, scanner, OMR and so on, with validation and verification.
- Processing: calculating, sorting, classifying, summarising, merging and comparing data, e.g. computing totals, averages and positions.
- Storage: keeping data and results on secondary storage for future use.
- Output: producing results as screen displays, printed report cards or files.
- Dissemination (distribution): sending information to the people who need it: parents, the principal, an examination body.
Some textbooks summarise the cycle as input → processing → output → storage, with feedback, which is the IPOS model from cs1.
Coding data during preparation saves space and reduces typing errors: “Male/Female” becomes M/F, states become two- or three-letter codes, and grades become A1–F9. Codes must be short, unique and easy to remember.
Methods of processing
- Batch processing: transactions are collected over a period and processed together, e.g. monthly payroll, electricity bills.
- Real-time (online) processing: each transaction is processed immediately, e.g. ATM withdrawals, airline seat booking, CBT exams.
- Time-sharing and distributed processing share computing between many users or computers.
Describe the steps involved in producing end-of-term report cards using a computer. (6 marks)
Collect scores from teachers; prepare and check them; input them into a spreadsheet with validation; process totals, averages and positions; store the file and a backup; print report cards (output) and distribute them to parents (dissemination).
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Practice questions
- field (data item)
- record
- file
- database
Show answer
A: field (data item)
Character → field → record → file → database.
- file
- byte
- database
- record
Show answer
D: record
E.g. one student’s details.
- online processing
- interactive processing
- batch processing
- real-time processing
Show answer
C: batch processing
E.g. payroll at month end.
- backup file
- master file
- transaction file
- reference file
Show answer
B: master file
Transaction files hold temporary changes.
- serial file
- sequential file
- random file
- indexed file
Show answer
A: serial file
Sequential files are sorted by key.
Key words
- Data processing
- Converting data into information by collecting, organising, calculating and outputting it.
- Data item
- A single fact, such as a name or a score.
- Field
- A space in a record for one type of data item, e.g. Surname.
- Record
- A collection of related fields about one person or thing.
- File
- A collection of related records stored under one name.
- Database
- A collection of related files organised for easy access and management.
- Key field
- A field whose value is unique for each record and identifies it.
- Master file
- A permanent file holding the main, up-to-date data of an organisation.
- Transaction file
- A temporary file of changes (transactions) used to update a master file.
- Reference file
- A file of fairly fixed data used for look-up, e.g. price lists.
- Serial file
- Records stored one after another in the order they arrive.
- Sequential file
- Records stored in order of a key field.
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