Blog Journeys of a Lifelong Learner

Users would be greatly benefited by an understanding of these main properties of operating systems:

1. User Command Interface
This is the interface from which the user issues commands to the operating system. Also called the “shell” (container inside which the entire user interface is presented), this is the visible interface with which users interact. For most users, the User Interface is the operating system.

2. Device Manager
This component monitors all devices, channels, and control units. The Device Manager must select the most efficient method for allocation of a system’s devices, printers, terminals, disk drives, and other hardware. This is based on a pre-determined scheduling policy, and the Device Manager makes allocations, starts operations, and ultimately deallocates devices.

3. Processor Manager
This component is responsible for allocating the central processing unit (CPU). The status of each process must be tracked, and the Processor Manager handles matters such as process prioritization and multithreading. The tasks of the Processor Manager can be divided into two main categories: accepting or rejecting incoming jobs (handled by the Job Scheduler) and determining which process is given access to the CPU and for how long (handled by the Process Scheduler).

4. Memory Manager
This component controls main memory. It evaluates the validity of each memory request, and allocates memory space (as needed and available). For multi-user systems, the Memory Manager maintains a log of what memory resources are in use by which users. When items stored in main memory are no longer needed, the Memory Manager handles memory deallocation.

5. File Manager
This component tracks every file in the system. These files include data files, assemblers, compilers, and applications. The File Manager can use predetermined access policies to enforce restrictions on file access. It also handles all other file permissions. The File Manager allocates file resources by opening a particular file and deallocates resources by closing the file.