Modes of operation

Computers can operate in many different ways requiring different and complex operating systemsoperating system: an interface between hardware, eg a computer, and the user.

Real-time processing

When the computer has to react within a guaranteed time to an inputinput: the term denoting either an entrance or changes which are inserted into a system and which activate/modify a process, a real-time operating system (RTOS) is used. For example, the engine management system within a car uses a real-time operating system in order to react to feedbackfeedback: a product of the initial event, eg temperature falling below an acceptable level in a greenhouse, that results in a subsequent modification of the event, ie heater turns on to raise the temperature back to an acceptable level from sensorssensor: an automatic input device that continuously monitors a set of computer controlled parameters, eg a parking sensor detects how close a vehicle is to the nearest object and alerts the driver if the distance falls outside of the specified parameters placed throughout the engine.

A real-time operating system does not necessarily have to be fast. It simply has to be quick enough to respond to inputs in a predictable way. Embedded computers often contain an RTOS as many are used to control something.

Computers operating in real time are often dedicated to the control of systems such as industrial processes, planes and space flights.

Multi-programming

Multi-programming is a method of operating such that several programsprogram: a list of instructions written in a programming language appear to be running at once.

The operating system switches jobs in and out of processorprocessor: shorthand for central processing unit (CPU) time according to priority. For example, while one job is being allocated printer time, another will be being processed in memorymemory: used to store data. The processor is so fast that it seems that many jobs are being processed at the same time.

Batch processing

A batch processing system is where programs or data are collected together in a batch and processed in one go. Typically the processing of payrolls, electricity bills, invoices and daily transactions are dealt with this way.

This method of operation lends itself to jobs with similar inputs, processing and outputsoutput: the term denoting either an exit or changes which exit a system and which activate/modify a process where no human intervention is needed. Jobs are stored in a queue until the computer is ready to deal with them. Often batch processed jobs are done overnight.

Interactive processing

An interactive processing system is where the tasks on the computer system require a continual exchange of information between the user and the computer system. It can be seen as the opposite of batch processing.

Multi-tasking

This isn't just about running more than one applicationapplication: applications serve a specific purpose, eg Microsoft Word is used for word processing at the same time. Multi-tasking allows multiple tasks to run concurrently, taking turns using the resources of the computer.

This can mean running a couple of applications, sending a document to the printer and downloadingdownload: the transfer of a file or files from one computer connected to the Internet to another a web pageweb page: a page designed for, and viewed in, a web browser.

Multi-access or multi-user

Modern personal computers can allow multi-user access. A multi-access (or multi-user) system is one where several users can use the same system together via a LANLocal Area Network (LAN): a network of computers that covers a small area, eg a school or college.

The CPU (central processing unit)Central Processing Unit (CPU): programs are executed by the CPU, it is an integral part of any computer deals with users in turn; clearly the more users, the slower the response time. Generally, however, the processor is so fast that the response time at the most is a fraction of a second and the user feels they are being dealt with immediately.

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