Operating resources (IT)
Operating resources or system resources (or simply resources ) are system elements of a computer that are required by processes for correct execution, such as e.g. B. hard disk , RAM or printer . Access to the resources is regulated by the operating system. In order to avoid conflicts, semaphores are usually used here that restrict access to the resource assigned to them. In interdependence of resources a failure of the access control leads to a so-called deadlock ( deadlock ).
Some resources such as B. Printers can only do one job at a time, which requires the use of so-called printer queues ( spooling ). With the resource CPU, on the other hand, the use of a scheduler can guarantee a fair distribution of the available computing time to all running processes.
Equipment can be classified in various ways:
- Hardware and software components
- The software components include all programs and data. Hardware components are e.g. B. the processor , memory , screen , printer ...
- Exclusive and simultaneous usability
- A resource can be used exclusively if only one process can access it at a certain time . For example, a file that has write access can only be used exclusively by one process. In contrast, a file can be read by several processes at the same time.
- Single and multiple use
- Unlike resources that can be used more than once (e.g. the processor), resources that can be used once are used up after access (e.g. printer paper).
- Withdrawable and non-withdrawable ( preemptible, non-preemptible )
- Resources that can be withdrawn (e.g. memory) can be withdrawn from the process that currently needs them and assigned to another process. Non-withdrawable resources, such as B. the printer must remain with the process until the end of the activity.
When programming specifically, one delimits files or parts of files with “resource” that provide background information on the program flow.
- Mandl, Peter .: Basic course operating systems: architectures, resource management, synchronization, process communication, virtualization . 4th edition Springer Vieweg, Wiesbaden 2014, ISBN 978-3-658-06217-0 .