3-14. ON-LINE PROCESSING
a. Various Uses of the Term. The term on-line can be used in several ways.
Since these several meanings can cause some confusion, it is best to clarify the term at
the outset. A peripheral device is said to be on-line when it is directly connected to and
capable of unassisted communication with the CPU. On-line also describes the status
of a person who is communicating directly with the CPU without the use of media such
as punch cards or magnetic tape. And finally, on-line refers to a method of processing
on-line: in direct communication with the computer; cabled to the computer;
information that is immediately accessible to the computer (stored on the
secondary storage that supports direct access to the information).
b. Description. On-line processing was developed as an answer to the batch-
processing deficiencies noted earlier. On-line communications systems allow the
transaction to be entered directly into the computer at the instant the transaction occurs,
rather than accumulated before inputting as in the batch mode. Normally, a keyboard
terminal is linked by means of a communications line directly to the computer where the
master files are located. In contrast to batching, on-line (direct access or random
access processing) permits data to be fed under CPU control directly into secondary
on-line storage devices, from the point of origin without first being sorted. Information
contained in any record is accessible to the user without the necessity of a sequential
search of the file and within a fraction of a second after the inquiry has been
transmitted. Thus, on-line processing systems may feature random and rapid input of
transactions and immediate and direct access to the record contents, as needed. The
information is said to be on-line when it is immediately accessible to the computer. On-
line systems do not necessarily demand a response. The Internal Revenue Service, for
example, absorbs a great deal of financial data, but only responds to those returns with
errors or requiring an audit.
on-line processing: the entry of data directly into the computer from a terminal
in direct communication with CPU (in contrast with batch processing); rapid and
random input of data without sorting; data manipulation fast enough to affect the
outcome, but not instantaneous.
c. Advantages and Disadvantages. On-line processing permits the computer
to interact with people as it processes a transaction. Much of the clerical burden of
paperwork is shifted from people to machines, when the computer is on-line to the
people doing the work. The two disadvantages of on-line processing are the complexity
of the process and the extra computer hardware and software needed. The CPU must
be adequate to handle the complex on-line system, as well as serve its other functions.
Since many on-line users have access to stored records, software security must be
adequate to protect against damage or unauthorized use. Processors must be fast