Operating System as a Resource Manager:
A computer system consists of various resources: processor, memory, channel and input/output devices, programs and data files. The operating system manages these resources effectively. As a resource manager, the operating system performs the following functions-
- Keeps track of the status of each resource.
- Decides which job should get the resource and for how much time.
- Allocates the resources to the job decided.
- Reclaims the resource after the job uses it for the allocated time.
These functions for each of the four resources, namely, processor, memory, devices, and files are given below.
Processor Management Functions:
- Keeps track of the processor by recording whether the processor is busy and if so who is using it.
- Decides which job should use the processor and for how much time.
- Allocates processor to the job decided.
- Reclaims processor after use for the allotted time.
Memory Management Functions:
- Keeps track of memory by recording which memory locations are in use by which program and which memory locations are free.
- Decides which job should get memory and for how much time in case of multi-programming.
- Allocates the memory space to the job.
- Reclaims memory after use to make it available to other jobs.
Device Management Functions:
- Keeps track of input/output devices and channels. That is, which device is in use and by which job.
- Decides which job should use the device, and for how much time.
- Allocates the device to the job.
- Reclaims device after use.
- Keeps track of files, that is, which files are in use and by which jobs.
- Decides which job should use the files and for what purpose (read/write/append/execute).
- Allocates file for use.
- Reclaims file, which means, closes the file.