3.3.5, 3.5.6, 3.3.7
Batch, online and real-time processing

These descriptions refer to the time element of collecting and processing data.

In batch-processing the user won't wait around for results to appear or alter the process once it has started.

In batch-processing, the acces is often sequential, perhaps using a serial device like a magnetic tape drive.

The systems flowchart does not refer to algorithms but only to processes and devices.

In traditional data processing, the data files were typically sequential access and therefore held on tape.

These days, tape drives are relatively uncommon and disc files can be accessed either sequentially or directly as needed by the application.

On this page: [ batch | online/interactive | real-time | master & transaction files ]

Processing methods - batch, online/interactive and real-time

These refer to the basic data flow model we have seen before:

There are different ways of carrying out these tasks in a computer system; these have been broadly classified as follows:

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Batch processing systems (including payroll cheque processing)

As mentioned above, the key characteristic of batch processing is that all the data is collected first. In the simplest of payroll systems the hours worked by each employee need to be collected; similarly in cheque-processing systems a batch of cheques is collected to be input into the system in one go.

A systems flow chart is often used to describe such processes:

In cheque processing the cheque data is not input by hand but a direct data entry method is used. This will either be Optical Character Recognition ( OCR ) or Magnetic Ink Character Recognition (MICR ).

In this case the amount of money on the cheque will be encoded and then the appropriate amount can be deducted from the payer's account and added to the payee's account. Again, this is a simple view of the process.

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Interactive (online) processing
(including word processing & computer games)

In normal usage on-line means that a device is under the control of a computer but online has come to mean connected to a network or other computer system (in particular online relates to internet usage by people). The two terms are commonly used interchangeably.

Interactive or online processing means that data is processed by the system as it is entered - the user typically waits a short time for a response . Examples include booking systems (theatres, buses, airlines, hotels, etc) as well as applications like word-processing and games .

Because these applications respond right away to data input, the data files themselves are held on a fast-access medium such as a disc-drive. In addition, direct access would typically be used.

Word-processing a document might be represented in a systems flow chart as follows:

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Real-time processing (including air traffic control and patient monitoring)

Real-time processing is fast ; however, speed alone is not the only requirement. Some online systems, like the stock control system at a supermarket appear to operate instantaneously in reading barcodes and looking up prices.

The processing of input data and production of the output must take place in time to affect the next input to the system. For example, in the case of patient monitoring, a drug might be used to control the heartrate. The flow of this drug could be regulated by a computer system. Should the heartrate fall or stop, the drug flow must be altered immediately, before further readings are taken. In an air traffic control monitoring system, the display must be updated immediately the direction, speed, or height of the plane is altered.

Real-time processing is often associated with automatic data entry , this is when data is read from a sensor or other input device without human interaction.

The patient monitoring example might appear like this in a systems flow chart:

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Master and Transaction files

The Payroll processing demo shows the relationship between the transaction and master files.

Basically, the master file contains all of the data relating to a particular application (account holder details, employee details). The transaction file contains the data which will be needed to update the data file.

Updating is often one of three operations:

• editing or changing data (eg a change of employee address)
• adding data (eg, a new employee is added to the master file)
• deleting data (am employee leaves or is fired)

A useful exercise would be to consider how each of these activities is carried out as a batch process.

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