Batch Processing System: In batch processing, data are gathered from time to time and collected into a group or batch before they are entered into a computer system and processed. When batch processing is used, the input data are typically recorded on source documents before being converted into a machine-readable form.
On-line Systems: An on-line system is one in which the system interacts directly with the user. As soon as the user inputs data, it is processed immediately. The system validates data at various points, and ensures that correct data is being entered.
Real-Time Processing: Real-time systems are on-line systems with tighter constraints on response time. In these systems the data is processed and results are generated fast enough to influence on-going activity.
Time Sharing: As its name implies, it has the ability to process several tasks simultaneously. In the time-sharing mode, the computer switches from one job to the other at a rapid rate. The jobs are entered into the computer through different terminals connected to the computer by cables. After processing the first user's job, it proceeds to the second and then the third, for short bursts of time or 'time slices' before returning to the first user's job from where it was earlier suspended.
This cycle continues indefinitely: when one programme is finished it is replaced by another one.
Integrity, Fallback and Recovery: With any system whether batch, on-line, or real-time, there is a danger that the system might break down. Certain procedures need to be followed to ensure that data is not lost, or the exact amount of data lost is known.
Integrity: Features of the systems which make it less likely to fail, are classified as 'integrity'. This is the most vital part, since system crashes may result in the loss of data and time.
Fallback: There are some procedures which have been created for use when the system fails, e.g. in some airlines enquiry systems, when the system fails, the fallback procedure allows the terminals to keep collecting data, though without validation. This allows some work to go on even though the main computer is down.Recovery: This is the process of bringing back the computer into full use when the system fails. It involves bringing back the data, i.e. restoring the data back to the stage it was in before the break down.