Real-time processing is data processing that occurs as the user enters in the data or a command. Batch processing involves the execution of jobs at the same time. The main difference is that administrators can postpone batch processes, while real-time processes must occur as soon as possible.
The time between when the user inputs the data into the computer and when the computer performs the expected output is called the response time. Real-time systems have predictable response times. Outputs are successful if they are accurate and timely. Response times do not necessarily have to be fast. There is no speed where a process is considered real-time and all processes have some delay. A system is "real-time" when processing activities have deadlines. Batch processing does not have a specific moment at which tasks are completed, with tasks being completed when the computer is able to complete them, based on the processing demands of the tasks and the processing speed of the computer.
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A hard real-time system is one in which the failure to meet even one deadline indicates a complete system failure. With soft real-time, missing a deadline indicates that the system is not working at its peak. In batch processing, missed deadlines might mean that the computer needs more processing capacity to finish tasks.
Real-time systems are usually reactive, meaning they behave based on the conditions of the environment. Real-time processors are usually embedded, meaning they do not have an operating system interface and are used only to control hardware devices. For example, a digital thermometer might have a real-time processor embedded in the thermometer that gives a continuously correct temperature. Batch processes are usually a part of a larger computer system.
Predictability Vs. Flexibility
Real-time systems have specific and predictable outputs that occur in response to an input. The number of outputs that a real-time system can have is usually fixed. For example, on the thermometer, the number of readings the thermometer has is fixed and the thermometer will not perform unique actions, such as reading "the meat is done." Administrators can usually adjust batch processes to serve different purposes.
With batch processing, processes are saved for when the computer is not executing very many tasks, such as in the evening when a business is not very busy. For example, a company can refrain from running antivirus scans when the company is busy, since the scans use up computer processing power. Administrators often start antivirus scans at night, when most of the workers have gone home. Real-time processing usually occurs whenever the processor receives an input.
Batch processing also occurs outside computers. For example, instead of sending a bill to a customer every time the customer pays for a service, a company might send a bill every month so that the company doesn't have to spend as much on postage. Real-time processing usually only refers to computers and microcontrollers.