SS2 2ND TERM COMPUTER STUDIES (2017/2018 ACADEMIC SESSION)

SCHEME OF WORK

WEEK	TOPIC
1	·         REVIEW OF FIRST TERM EXAM QUESTION ·         WRITING THE SCHEME OF WORK
2-3	CONCEPT OF COMPUTER FILES ·         Definition of terms – Data, field, record, file ·         Types of data items ·         Types of file organization method ·         Method of accessing files ·         Computer file classification ·         Criteria for classifying computer files
4-5	HANDLING COMPUTER FILES ·         Basic operations on computer files ·         File insecurity and its effect ·         Methods of file security ·         Advantages /disadvantages (Limitations) of computer file ·          Differences between computer files and manual file
6-7	SYSTEM DEVELOPMENT CYCLE (SDC) ·         Definition of System Development Cycle ·         Description of the stages in the SDC

Note: The Scheme of work is subject to changes as an addition of 1 more topic is HIGHLY probable.

TOPIC 1: CONCEPT OF COMPUTER FILE

Definition of terms

• 1.       Data: a raw fact that has not been processed.  It is the smallest unit (an item) of information e.g. James, 45, Male etc.
• 2.       Field: it is a space/named area of a record allocated to store an item of information, e.g. Name, Age, Gender etc.
• 3.       Record: It is a collection of related data items or fields about an entity i.e. a person, thing or place. For example, a student record may consist of his/her gender, name, age etc.
• 4.       (Computer) file: A file can be defined as a collection of related records that give a complete set of information about a certain item or entity.

A file may also refer to an object on a computer that stores data, information, settings, or commands used with a computer program. In a graphical user interface (GUI) such as Microsoft Windows, files display as icons that relate to the program that opens the file.

A file is created using a software program on the computer. For example, to create a text file you would use a text editor (notepad), to create an image file you would use an image editor (paint,corel draw etc.), and to create a document you would use a word processor (Microsoft Word, Word Perfect etc).

Computer files are stored on a drive (e.g., the hard drive), disc (e.g., DVD), and a diskette (e.g., floppy disk) and may also be contained in a folder (directory) on that medium.

Every created file has an extension. A file extension or file name extension is the ending of a file that helps identify the type of file in operating systems, such as Microsoft Windows. In Microsoft Windows, the file name extension is a period that is often followed by three characters, but may also be two or four characters long. As an example the file name "myfile.txt" has a file extension of ".txt", which is a file name extension associated with text files.

Assignment:

List the type of file associated with each of the following file extensions:

1.”.3gp”                2. “.exe”              3. “.dll” 4. “.bat”               5. “.html”             6. “.cmd”            

7. “.rtf”                 8. “.accdb”                          9. “.pptx”                             10. “.cdr”

Types of data items

The following are types of data (item):

·         Numeric data: these consists of digits (0-9) e.g. 1, 43, 0.56 etc.

·         Alphabetic data: these consists of alphabetic characters (A-Z or a-z) only e.g. School, Bond, Name etc.

·         Alphanumeric data: these are data made up of combination or alphabets and numbers.

Types of File Organisation Method

File organization is a way of organizing the data or records in a file. It refers to how the contents of a file are added and accessed, but not how files are organized in folders. The four file organisation methods are:

• 1.       Serial file organisation: records are stored in the order they occur. They have not been sorted in any particular order.
• 2.       Sequential file organisation: records are stored in a sorted order of a particular field(s), usually the key field(s).
• 3.       Indexed file organisation: An indexed file contains records ordered by a record key. A record key uniquely identifies a record and determines the sequence in which it is accessed with respect to other records.
• 4.       Random or direct file organisation: records are stored randomly in no particular order i.e. in any sequence

Methods of Accessing Files

Access method is a mechanism or manner in which the records in a file may be accessed.  It defines the way the read and write operations are done. The methods of accessing files include:

• 1.       Sequential access: a sequential file access is that in which the records are accessed in some sequence i.e., the information in the file is processed in order, one record after the other. It requires the program to start writing or reading at the beginning and continues until it finds the desired data. Device like magnetic tape enforces sequential access method.
• 2.       Direct/random access: the records on the storage location can be accessed (read or written to) in any order i.e. randomly/directly. Devices such as magnetic disk storage and the main storage i.e. RAM and ROM are based on this method.
• 3.       Indexed-sequential access: this mechanism is built on the basis of sequential access. An index is created for each file which contains pointer to various records (blocks). Index is searched sequentially and its pointer is used to access the file directly.

Computer File Classifications

Computer files can be classified as follows:

• 1.       Master file: This is a computer file that is used as the authority in a given job that is relatively permanent. It is a permanent file, periodically updated, that serves as an authoritative source of data. It is an original file from which duplicates are made.
• 2.       Transaction file: It is a computer file containing relatively transient data about a particular data processing task. It is a file, especially a data file, containing transaction records, used to update the master file.
• 3.       Reference file: This is a computer file containing data, which is kept so that it can be referenced for future use. It is stable and permanent in nature.

Criteria for classifying computer file

Computer files can be classified according to the following criteria:

1.       Nature of content: files of similar contents are classified together. Examples are database file, word processed file etc.

2.       Organisation method i.e. whether sequential, direct etc.

3.       Storage medium: whether they are stored in tapes, disks or any other storage devices.

TOPIC TWO: HANDLING COMPUTER FILES

Basic operations on Computer files

The following are some of the basic operations on a computer file:

• 1.       File creation: using an application package to create a file
• 2.       File deletion: an unneeded file can be removed (deleted) from the computer to free up disk space.
• 3.       File retrieval:  the file is brought out from where it is located for further processing
• 4.       File copy: process of making duplicate copies of a file
• 5.       File open: files are loaded (opened) before it can be used. The content are being displayed on the screen
• 6.       File close: when you are done with a file and need to free up main memory space, you close the file.
• 7.       File read: The file read operation is performed just to read the data that are stored in the required file. No addition is done to the file.
• 8.       File Write: The file write operation is used to write the data to the file, again, generally at the current position.
• 9.       File Update: making changes to the content/records of a file
• 10.   File Rename: The file rename operation is used to change the name of the existing file.

File insecurity and its effect

File insecurity is a concept that a file is always vulnerable and is prone to be lost or missing in the computer. Virus attack, careless deletion of files, hardware failure/malfunctioning etc. are some of the causes of file insecurity.

The following are the effects of file insecurity:

1.       Loss of data

2.       Data unreliability

3.       Data corruption

 

Methods of File Security

The methods of file security include:

1.       Use of backup: make copy of computer files on DVD, external HD, CD etc.

2.       Use of antivirus: install and update antivirus to avoid virus attack

3.       Passwords:  Password your computer to prevent unauthorized access to the files.

4.       Proper labeling of storage devices: this helps in identifying what file is stored in a particular storage device

5.       Disk/directory/file encryption: encode/encrypt the file to make it meaningless to anyone that may have unauthorized access to it.

6.       Physical security: e.g. security guards, alarm systems, lock on rooms and on computer etc.

Advantages and disadvantages of computer file

Advantages

1.       Faster and efficient in processing of information

2.       More secure

3.       Fast to access

4.       Uses less space

5.       More accurate

6.       Can be updated

7.       Permits long term storage and retrieval

Disadvantages/limitations

1.       Expensive to set up

2.       Require power supply

3.       Data are often duplicated

4.       Can be corrupted

5.       Vulnerable to virus attack

6.       Requires formal training to handle

Differences between Computer Files and Manual Files

Computer files	Manual files
More secured	Less secured
More reliable	Less reliable
Can easily and neatly be modified	Cannot be easily and neatly modified
Fast to access	Slow to access especially if there is large number of file to check from
Can be attacked by virus and worms	Can be attacked by rodents, insects, fire etc.

TOPIC THREE: SYSTEM DEVELOPMENT CYCLE (SDC)

Software Development Cycle (SDC) or Software Development Life Cycle (SDLC) is a process that consists of a series of planned activities to develop or alter an Information system.

System development Cycle can be thought of as a set of activities that analysts, designers and users carry out to develop and implement an information system.

Stages in the SDC

The diagram below shows the stages involved in the SDC, starting from the initial stage i.e. the preliminary study to the study review stage. Note that since this is a cycle, the event may be repeated.

The stages in the SDC include the following:

• 1.       Preliminary
• 2.       Feasibility study
• 3.       Investigative
• 4.       Analysis
• 5.       Design
• 6.       Implementation
• 7.       Maintenance
• 8.       Study review

Description of the stages in SDC

1.  Preliminary: The intended goal (i.e. what the system will do) of the project (information system) is established in this stage.
2.  Feasibility study: This is the study carried out before development of the system to ascertain if the proposed system is possible, practical and can serve a purpose.
3. Investigative: The project goals are restated into specific functions and operation of the intended system. Whatever the end-user want, how he/she wants it and when he/she wants it is considered and analysed here.
4. Analysis: The goal of the system analysis is to examine the type of the system on the basis of user requirements (what the user needs in the system).
5. Design:  Designing the system in terms of user interface, data storage and data processing functions on the basis of the analysis phase by developing system flowcharts, system and data flow diagrams, screen layouts and reports.
6.  Implementation: programming the system as designed and conducts the continuous testing and debugging. The user accepts it at this stage before migration to live environment.
7. Maintenance: This stage involves making changes, corrections, additions to the software while in use.
8. Study review: The system is continuously evaluated as it functions in the live environment; this is done to see if there is need for upgrade or replacement of the system.