Hierarchy of data
1.
Bit – smallest unit, consist of 1 & 0.
2.
Byte/Character – eight bits, alpha-numeric and
special characters.
3.
Field – combination of two or more characters,
column of a database.
4.
Record – combination of two or more related
fields, row of a database.
5.
File – combination of two or more related
records.
6.
Database – combination of two or more related
files, intersection of field and record.
Types of files
A.
According to function
a.
Master file – static view of some aspects of an
organization, no deletion of data.
Example: Transcript of record
b.
Transaction file – changes that are applied to
the master file.
Example: Receipt/OR
c.
Program file – contains instruction for the
processing of data.
Example: Visual basic program
file, File.vbp
d.
Work file – a temporary file. Files in progress.
Example: File.temp
e.
Report file – formatted for presentation to a
user.
Example: Power point
presentation, File.ppt
f.
Text file – contains alphanumeric and graphic
data input using a text editor program.
Example: Word file, File.docx
g.
Security file – used to protect and protect
changes to a certain file.
Example: Password
h.
Audit file – contains audit and error listing that
includes all transactions process.
Example: Users.log
B.
According to mode of access
a.
Input – read by the program.
b.
Output – written to by a program.
c.
Input/Output – both read from and written to
during program execution.
File Operation
A.
Batch mode – process of transaction accumulated
over a period of time. The performance is measured by throughput.
B.
Interactive mode – transactions are processed as
they arrived. The performance is measured by response time.
Fundamental File Operations
A.
Creation – loading of a file.
B.
Update – changing the content of a master file
to make it reflect a more current snapshot of the real world.
Changes
may include:
Ø
Insertion of new record.
Ø
Modification of existing record.
C.
Retrieval – the access of file.
a.
Inquiry – low volume response.
b.
Report – create many pages of output.
Retrieval
request can be:
Ø
Comprehensive – retrieval reports inform action
from all the report information from all the record in a file.
Ø
Selective – retrieval applies more qualification
or criteria to chose which record will supply information for output.
D.
Maintenance – change of mode to file to the
purpose of improving the performance of program that access them.
a.
Restructing – a file implies that structured are
mode to the file within the context of the same file organization.
b.
Reorganization – implies change from one file
organization to another.
Methods of Organizing Data
A.
Sequential – records are stored in order
according to a key field. If a particular record is desired, all prior records
must be read first.
Example:
Tape storage
B.
Direct – also called as random access. Go directly
to desired record by using a key.
Example:
MP4 player
C.
Indexed – combines elements of sequential and
direct methods. Records are stored sequentially, but file also contains an
index, data accessed by a record key.
Example:
Dictionary
Record key
A.
Primary – search the record uniquely.
Example:
Student number
B.
Secondary – search the record but not uniquely.
Example:
Surname
C.
Foreign – combination of primary and secondary.
Example:
Full name and school attending
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