COMPUTER FILES

MEANING OF FILE:
A file may simply be defined as an attempt to organized related information, or a collection of records. In practice, a file in computer terms is the essential input for processing program. Some systems require you to set up your programs as individual files; you read the (program) file into memory, and the file contains all the instruction you need. Data files contain all the data a particular program needs; a subscription program might use one file or subscriber records, another with subscription rates.

The system of creating a file on computer is not different from the traditional way - used in an office. Each form in a file is know as a record, so many forms (records) are kept in a file. Different files contain different information. This system is used in the computer system. A file contain records for a particular subject.

FILE NAME
All the information we have in the computers are stored on magnetic materials. The most common storage media for computers are floppy disk (diskette) and hard disks. The information we stored on the storage medium is kept as a file, importantly every file must be given a name, and this is called File name. The computer might not accept a creation of another file with already existing name. But the same can be accepted if they are in different folders (Directories). A file can either be a system or user's file.

System File: These are the files supplied by the manufactures of the computer systems.
User's file: This is the file created by the computer users for keeping processed and unprocessed data.

Types of Files
Historical File: One type of file is the historical or dead file. This contains document no longer necessary for either current reporting or for the preparation of other documents. Data or the documents in these files have already been applied to all the records which it affects, and all necessary action has been taken on the records.

A completely processed purchase order is an example of this type of file. The goods have been received, paid for, and charged to the department which ordered them.

Library Files: A second type of file found in most offices is the library file. This contains records not affected by transactions but used for reference by various personnel in the office. Such files are used to store procedure manuals, policy bulletins and the like. Their basic function is to define guidelines for performing various activities in the office, as opposed to recording the activies of the business. These files are updated only when a procedure or policy becomes outdated or replaced. Library files may be actual or inactive.

Open Files: A third type of file is the open or tickler file. These contain the same kind of records as the historical files. They differ in that the processing of transaction has not yet been completed in an open file. They may include purchase order not yet received, unpaid and purchase orders, unfilled sales orders and unanswered correspondence.

FILE ORGANISATION
Master - file: This is a file of fairly permanent nature. It is usually used to keep the details of students in an institution or all customers in an organization.
Transaction File: This is otherwise known as movement file. It is temporary in nature. This type of file contains different transactions created from the source documents. It is normally used to update the master file.
Reference File: It is used to store data needed for reference purposes. It is usually fairly permanent in nature. Examples of reference file include, price lists, table of rates of pay, names and addresses, etc.
File Accessing: This refers to the methods the contents of a file can be reached and used for processing.

TYPES OF METHODS OF FILE ORGANISATION
It is a common knowledge that many files contain several records. The organisation of the records on the storage disks can help in how fast the data can be retrieved. There are three types or methods of organising records in a file. These are sequential, indexed and direct access.

SEQUENTIAL ORGANISATION: in sequential file, records are physically stored in sequence or order. In other words, the records are placed in one after the other unto the medium concerned without arranging them in any other. This means that the reading will be done record by record. Sequential files can only be accessed sequentially. For examples if you search to know the address of a student with number 5, you must first pass the first 4 records on disk to access the required record.

Indexed Files: This is the most commonly used file organization for storing records on disks. It uses an index based on the key field of records. A key-field is a field that uniquely defines a record that can be accessed quickly and easily. The major advantages  of indexed file method are: (1) it makes it possible for frequent updating of large quantities of data without the problem of re-arrangin or sorting the records. (11) it also makes it possible for the records to be located quickly without going through the process of sequentially reading the disk. However it should be noted that this method cannot be used with tapes.

Direct Access Files: To direct access file, The key field is used in some way as the address itself, this solve the problem of first looking at the index. Direct access is most appropriate for on-line operations that needs the highest speed for retrieval and updating of records. The beauty of this method is that any part of the file can be accessed by using a key to search for the record.

BASIC OPERATION COMPUTER FILES
Basic operations on computer files are as follows:
Creation
Deletion
Retrieval
Copy
View
Updates
Open
Clos

EFFECTS OF FILE INSECURITY
Loss of Data
Overwriting

METHODS OF FILE SECURITY
Use of back Ups
Use of Anti-virus
Use of Password
Proper label of storage devices etc.

ADVANTAGES OF COMPUTER FILES
The files are more secured
They are very fast to access
Less laborious
They are more reliable.
They are neatly modified

LIMITATIONS
Expensive to set it up
Irregular power supply