Online and offline processing
Online processing
The term 'online' processing is the term used to describe when a user is connected to a computer or network (they are logged in) and are processing the data files at the same time as using the input, output and storage devices.
Offline processing
To help speed up data input and output into computer systems, offline processing was 'invented'. This removes the need for relatively slow input devices. Instead, data is stored in files on a high-speed data storage device. This could be done in a number of ways. For example, an operator might use a different computer system to simply type in data from paper forms into a file, perhaps using a key-to-disk system or if the data was in a machine-readable form (such as OMR sheets), it could be read automatically and stored in a file. Then, when the computer is ready, it can get all the data it needs from these files on the high-speed storage device rather than from relatively slow input devices.
This is described as offline processing because the main computer doing the processing is not immediately controlling and reading the data from its input devices. The data is being prepared and stored away from that computer on a high-speed storage device and is then made available as necessary.
More examples of online and offline processing
A 'network' is a number of computers (more than one) that have been physically connected together. This enables them to communicate with each other and share files and share hardware such as printers. A computer that is part of a network can be either 'online' or 'offline'. If it is offline then it is physically connected to the network but not actually using the resources of the network. It is not logged in to the network. For example, you may have a computer at home that has a modem plugged into your telephone socket. This is known as a 'dial-up connection'. Your computer is part of the Internet. Some people, however, write their emails 'offline'. This means that they actually write their emails without logging on to the Internet. They are writing emails offline because they are not actually using the resources of the network. When they want to send their emails, however, they need to log on to the Internet. As soon as you connect to the Internet via your Internet Service Provider, or ISP, then you go online. You are using the resources of the network to send emails. You are physically connected to the network and you are logged into the network. This is just one example of the meaning of 'online' and 'offline'.
'Online' and 'offline' are terms usually associated with networks. They describe whether a computer or workstation is or isn't using the resources available on the network. In particular, it describes whether or not they are using the processing power available on the network. If the computer or workstation is using the network's processing power then it is said to be online. If it isn't (but is physically connected) then it is said to be offline. The email example is one example where you can be either online or offline. There are other examples. Someone working on a network might be typing in data into a file on their workstation's disk. They are working 'offline'. If this data is then used to update a master file held on the server then the user will go online to do this. They contact the server by logging in, tell it where to find the data stored on disk, the server processes the data and the master file is updated.
Consider another example. Somebody who wants to ask you some questions for a questionnaire stops you in the street. As you give your answers to their questions, they record your responses directly into a database on their tablet PC. When the interviewer goes back to the office, they transfer all of the responses of all of the people that have been interviewed into the master database held on a central computer. The data is collected offline (because the interviewer is not using the processing power of the main computer) but the data is transferred and analysed online, because the processor in the main computer is required to transfer the data and to work on it.