Page 98 - DCAP516_COMPUTER_SECURITY

Computer Security

Notes can be usable either by an individual or by any number of users, can be labelled as data processing
mechanism. For data processing, these steps are generally followed:
1. Data Source: The first step is to obtain the relevant facts and figures and to set these out on
source documents, for example, in a population survey, the name, address, age, sex,
occupation, etc., must be first written down on to a survey sheet or some other documents.
These documents may be so designed that information is recorded in the required order.
2. Data Input: Once the data has been extracted from the source document, it must then be
transferred into some form suitable for data entry into the computer so that processing
can take place. The method will depend upon the input media and the devices.
3. Data Manipulation: Information, inputs for processing may have to be classified or sorted.
It is this form of operation, or data manipulation, rather than pure computation, with
which data processing is mainly concerned. For example, in the population survey, we
may want to classify people by occupation or by age. We may wish to sort lists on
alphabetical order or in any other order. We may require employees to be grouped by
departments for a pay roll program. All these forms of data manipulation will produce
results, which can be organized in the form of summaries.

4. Data Output: The objective of results or summaries is to provide meaningful information
to managers, accountants, etc., and careful consideration, therefore, should be given to the
presentation of results so that they can be understandable easily and quickly.
5. Data Storage: In most cases, the results of processing are retained for future use or reference.
In many cases, it may be necessary after updating, to compare the latest figures with the
previous figures, perhaps, over different periods of time. This means that data processing
installations require a great deal of secondary storage space to store all the programs and
the different sets of data.

8.5 Types of Data Processing

Basically, there are two types of data processing:
1. Batch Processing: With batch processing, changes and queries to file are stored for a
period of time, and then a processing run is made periodically to update the file and to
produce responses to the queries. Batch runs can be made on a scheduled basis, such as
daily, weekly, or monthly, or they can be made on an as required basis. Examples of batch
processing include generation of mark-sheets of students. Mark-sheets and results of school
examinations are given to students only at the end of an academic year. So, a programmer
can develop a program for this and the results can be printed at the required time.
2. Online or Immediate Processing: In immediate processing, transactions are processed to
update the file immediately or shortly after a real-world event occurs. Information
processing applications that use immediate processing are often called real time
applications. A real time application can immediately capture data about ongoing events
or processes and provide the information necessary to manage them. An airline-reservation
system is an example of a real time application. Real time systems must have real time
files that are updated immediately after the event occurs. Consequently, at any point in
time, the data in real time files should accurately reflect the status of the real world
variables they represent. For example, when a customer reserves a seat on an airline
flight, the reservations agent keys in that fact and the inventory of non-reserved seats on
the flight is immediately changed to reflect one less available seat. Immediate processing
requires direct-access files, since immediate processing with sequential files would be
impractical because of the time required to search for individual records. Batch processing,
on the other hand, can occur with either sequential or direct access files. Examples of

92 LOVELY PROFESSIONAL UNIVERSITY