®
Recommended prior knowledge
It will be helpful if students have studied Unit 6 before starting this unit.
Context
Students need to study this unit before or alongside Unit 12. For this unit, together with Unit 7, Computer Studies Support Booklet – Part 4
( http://teachers.cie.org.uk/docs/dynamic/31799.pdf
) provides notes on section 4 of the syllabus and practice problems (with answers in Computer Studies Support
Booklet – Answers ( http://teachers.cie.org.uk/docs/dynamic/31801.pdf
).
Outline
The relationship between data and information; methods of data collection, encoding and preparation; appropriate methods of ensuring the correctness of data
(including validation and verification); methods of automatic data capture; analogue-to-digital and digital-to-analogue conversion.
File organisation: different forms of organisation and storage medium, depending on the data stored and the requirements for processing; sequential file processing and processing individual records by means of record keys; sorting and merging; methods of processing and file maintenance.
Data types: numbers, characters, strings, arrays and the need for different data types and structures to represent the data for a particular application.
Syllabus ref
Learning objectives
Suggested teaching activities Learning resources between data and information information as appropriately presented processed data.
Collection of data It is helpful to distinguish between data collection prior to entry, often on paper forms and methods of data capture (when data actually enter the computer).
Students need to describe different data capture methods and learn when their selection is appropriate:
LWS coursebook pp. 30–1 www.teach-ict.com/ks3_old/unit9_1/miniweb/pg3.htm
Simple illustration of Input, Process & Output www.teachict.com/gcse/theory/datainfo/student/shome_datainfo.htm
Theory notes, activities and quizzes on data and information (ignore knowledge for this syllabus)
LWS coursebook pp. 31 and 32–3 www.teachict.com/gcse/software/datacapture/students/shome_datac apture.htm
v1 2Y04 Cambridge IGCSE Computer Studies (0420) 1

Syllabus ref
Learning objectives
Suggested teaching activities Learning resources
• manual input via keyboards and touch screens
• automatic data capture techniques:
• barcodes in automatic stock control systems
• OMR techniques in input of lottery entries and survey data
• OCR techniques in input of text in questionnaires
• sensors in data-logging.
Theory notes, activities and quizzes on data capture for input data and the reasons for its use.
Other forms of data preparation include ensuring that data are in a standard format.
Methods Explore web forms for examples validation and verification techniques and ensuring its correctness
(including validation and verification and the distinction between these)
ISBN codes as examples of ID codes with check digits, to help students learn to describe and select:
• validation techniques (e.g. range checks, type checks)
• the use of check digits (how check digits are generated and why they are used)
• verification techniques (e.g. double entry and visual checks) and their uses (e.g. checking password entries).
Although spreadsheet software does not apply type checks by default, students could perform practical exercises in both spreadsheet and database software to apply a range of validation checks.
Analogue-todigital and digitalto-analogue conversions
Consider how analogue (smoothly changing) data from a sensor (e.g. for temperature, moisture or pressure) can be input as digital (step-valued) data into a computer.
Explain that some sensors are effectively switches with digital outputs, but most have analogue output requiring ADC to produce digital data for a monitoring or control system.
Similarly, a monitoring or control system may only need to switch (or rapidly pulse) an output to a lamp or motor, but when an analogue
(smoothly changing) output is needed, a DAC is required.
Consider a computer sound card as an example of a device containing both sorts of converter and research other computers or devices requiring one or both sorts.
LWS coursebook p. 31 www.teachict.com/as_a2/topics/data_info_know/datainfo/coding_of_ data.htm
Introduction to encoding data
LWS coursebook pp. 33–7 www.teach-ict.com/gcse/software/db/miniweb/pg10.htm
Introduction to validation www.teach-ict.com/gcse/software/db/miniweb/pg11.htm
Introduction to verification www.bbc.co.uk/schools/gcsebitesize/ict/databases/3datav alidationrev1.shtml
First of two pages on data validation and verification
LWS coursebook pp. 31–2 www.teachict.com/gcse/software/control/miniweb/pg4.htm
Introduction to analogue-to-digital conversion http://gcsecomputing.org.uk/theory/1_4/1_4_sound.html
Introduction to ADC and DAC for sound v1 2Y04 Cambridge IGCSE Computer Studies (0420) 2

Syllabus ref
4.2.3
Learning objectives
Suggested teaching activities Learning resources different forms of organisation, depending on the data stored and the requirements for processing; processing methods
Data types for numbers, characters, strings, arrays; the need for different data types and structures to represent the data for problems being solved help students learn to describe:
• the need to process files
• file structure: field name, field type, concept of key field, relationship between fields and records and conventional presentation in spreadsheets and database tables
• file
• types of file: serial, sequential and direct (random) access
• their applications, e.g. serial file in a batch processing system, direct access in real-time transaction processing system.
• how files are processed
• file maintenance: updating/amending, inserting and deleting data from a file as appropriate, e.g. car sales business will insert data when a new car arrives, delete data when a car is sold and amend data if there is an error or they have a sale and reduce price and select with reasons, the appropriate file organisation and processing methods for a particular application.
Data types can be introduced by considering the different data types that may be used in the various fields within a record.
Students could perform practical work:
• on a sample database, to understand that a database program prevents inappropriate data entry partly through the use of type checks to distinguish between acceptable and unacceptable types of data on data entry
• on a similar sample spreadsheet, to understand that:
• a spreadsheet program accepts any string of characters entered into a cell and automatically interprets it as a particular data type, with text as the default type
• some other data types can be enforced by applying appropriate data validation to a cell, or range of cells.
This should help students to:
• identify the different forms of data and explain how the data is represented for processing
• explain the need for different data types and structures and how these relate to the data of the given problem.
LWS coursebook pp. 37–9 www.teachict.com/gcse_new/databases/terminology/miniweb/pg7.ht
m
Introduction to key fields www.cedar.u-net.com/ict6/demoidx.htm
Search for access to find direct and serial access
LWS coursebook pp. 39–42 www.teachict.com/gcse_computing/ocr/216_programming/handling_ data/home_handling_data.htm
Theory notes on data types v1 2Y04 Cambridge IGCSE Computer Studies (0420) 3