A system is a collective entity consisting of groups of elements that are interdependent, interrelated and that interact to achieve certain objectives. A system could be part of bigger system.

An information system performs five basic functions:
•    Input Function
•    Process Function
•    Output Function
•    Store Function
•    Control Function

The input function accepts the data; process manipulates the data to produce the output. The output function manipulates the output further to print and display reports, to update the record and so on. The store function writes the output to an assigned storage area. The control function validates the input, process, output and also ensures access to the system.

The functions mentioned there are independent of technology. Technology drives the system. It will influence the system in its performance but may not influence the logical flow of the system.

Input Function
The scope of the input function encompasses activities described as acquiring, accessing, receiving and entering. The impute may be entered through the data entry careen, or may be received form another system through an interface. The input function is performed through keyboard, scanner or interface devices and the acceptance or receipt of data may validate the input for further processing.

Processing Function
The processing function acts on validated input received form the input function. The processing function manipulates the data through different steps to produce a result. The steps in processing are logical, such as compute, sort, compare, sum up, interpret with rules, etc. These steps are organized (Programmed) in a logical flow to produce the result desired. The steps may start automatically through a stored procedure, based on the status of the result, or may be triggered through manual intervention.

A process function produces a result that may become the input to another process int eh same system or to a process in another system. Several process functions, organized in a logical order and which can manipulated the data and the intermediate output, are together called the Transaction Processing System. processing of orders, receipts, receivables and cheque payments are all part of the Transaction Processing System.

The ‘processing function may be executed in real time or off time in batch mode. The processing function thesis called Real Time and Batch. The choice of function is need based. A real-time process is needed when a response is required immediately, such as cash withdrawal through an ATM system. The batch process is preferred when such response is not immediately required and transactions can be excited in batch mode with time intervals. The transaction systems of booking worked hours, rejection data, wages for the week and so on can be processed in batch mode.

Output Function
The output function deals with results processed by the process function. The results need to be organized in a Form or Format and be produced in physical terms, such as report, display, or trigger other system. The output function uses report writers for printing reports using the results of the processing function. The output could be a report, document, image message or a trigger.

Invoice processing will produce several results such as net invoice amount, taxes to collect, discount and commission given and so on. The output function will use these results and print an invoice document in the name of the customer with a standard instruction set for dispatch, payables etc. On printing of the invoice, the output function will update the sales status of the product, and details of customer, distributor and so on.

Storage Function
The function of Storage is to store the data, intermediate results, or final outputs for use subsequently. The storage function changes the status of times in the database. This function could be manual or automated. The storage function uses steps such as “Create”, “Update”, “Read”, “Delete” and “Copy”. The functions is independent of where the data is stored, this location and media. It is stored at a given destination in the manner storage is defined.

Control Function
The control function is the brain of the system. This function puts intelligence behind the system. It deals with Inputs-Process-Output. Its role is to verify, validate inputs and outputs and ensure the integrity of stored data. Further, it points out errors for correction through manual or automated system intervention. There are two types of controls: general and application.

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