WAEC SSCE - Computer Studies - 2015 (Essay)

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(a) What is a computer file?

A computer file is a collection of related records or data stored together under one name on a storage medium, and treated as a single unit by the computer.

(b) Two features each

(i) Transaction file:

1. It holds temporary data about current transactions or events (for example daily sales) that are used to update the master file.
2. Its contents change frequently and it is usually not kept for long after the master file has been updated.

(ii) Reference file:

1. It holds fairly permanent data that is looked up (referred to) when processing, for example price lists or tax rates.
2. Its contents change only occasionally and it is used mainly for reference, not for continuous updating.

(c) Two of each

(i) Effects of file insecurity:

1. Loss, damage or corruption of data.
2. Unauthorised access, alteration or theft of confidential information.

(ii) Methods of securing files:

1. Use of passwords and access rights.
2. Encryption of files (and keeping regular backups / using anti-virus and write-protection).

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(a) Definition of operating system

An operating system is the system software that controls and manages the hardware and software resources of a computer, and acts as an interface between the user and the computer, enabling other programs to run. Examples are Windows, Linux, macOS and Android.

(b) Two functions of an operating system

1. It manages the hardware resources (processor, memory, input/output devices and storage).
2. It provides a user interface and controls the loading and running of application programs (and manages files and security).

(c) Two types of each

(i) Application software:

1. Word processing software (for example Microsoft Word).
2. Spreadsheet software (for example Microsoft Excel). (Database and presentation software are also acceptable.)

(ii) Translators:

1. Compiler.
2. Interpreter. (Assembler is also acceptable.)

(d) Two software to compile the personal data of final year students

1. Database software (for example Microsoft Access) to store and manage the student records.
2. Spreadsheet software (for example Microsoft Excel), or word processing software, to enter and tabulate the data.

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(a) Definition of algorithm

An algorithm is a finite set of clear, step-by-step instructions for solving a particular problem, arranged in a logical order so that following the steps produces the required result.

(b) Three characteristics of an algorithm

1. Finiteness - it must have a definite ending after a finite number of steps.
2. Effectiveness with input and output - it must take input (where needed) and produce at least one output, and every step must be doable. (Being general/applicable to a class of problems is also acceptable.)

(c) Algorithm for finding the average of numbers when the sum is given

The average is the sum divided by the count of numbers, \(Average = \dfrac{Sum}{N}\).

1. Start.
2. Read the sum of the numbers, SUM.
3. Read the count of the numbers, N.
4. If N = 0, display "cannot divide by zero" and go to step 7.
5. Compute AVERAGE = SUM / N.
6. Display AVERAGE.
7. Stop.

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(a) Two main constituents of a computer

1. Hardware (the physical parts of the computer).
2. Software (the programs that run on the computer).

(b) Four characteristics of a computer

1. Speed - it processes data very fast.
2. Accuracy - it gives correct results with very few errors.
3. Storage - it can store very large amounts of data.
4. Diligence / automation - it can work continuously without getting tired. (Versatility is also acceptable.)

(c) Categorising the statements as data or information

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(a) Definition of system development cycle

The system development cycle (system development life cycle) is the series of stages or steps followed in an orderly way to plan, analyse, design, build, test and put into use a new information system, and then to maintain it.

(b) Four stages involved in the system development cycle

1. Problem definition / feasibility study (identify the problem and decide whether a new system is worthwhile).
2. System analysis (study the existing system and gather requirements).
3. System design (design the inputs, processes, outputs and files of the new system).
4. Implementation, testing and maintenance (build, test, install the system and keep it running).

(c) Four qualities of a good program

1. Correctness / accuracy - it produces the right results.
2. Reliability - it works consistently without failing.
3. User-friendliness - it is easy to understand and use.
4. Maintainability - it is well structured and easy to modify. (Efficiency and portability are also acceptable.)