Process Management :- A process is program in execution. For the successful completion of its task a process it needs certain resources, including CPU time, memory, files and I/O devices. These resources are either given to the process when it is created, or allocated to it while it is running.

Main-Memory Management :- The main memory is central to the operation of a modern computer system. Main memory is a large array of words or bytes ranging in size from hundreds of thousands to hundreds of millions. Each word or byte has its own address. CPU reads instruction from the main memory during the instruction fetch cycle and both reads and writes data from main memory during the data fetch cycle. The main memory is generally the only large storage device that CPU is able to address and access directly.
For a program to be executed that must be loaded into the main memory. When the program terminates its memory space is declared available, and the next program can be loaded and executed.
The operating system is responsible for the following activities in connection with memory management:
• Keep track of which part of memory are currently being used and by whom
• Decide which process are to be loaded in to memory when memory space become available
• Allocate and deallocate memory space when needed

File Management :- File management is one of the visible components of an operating system .Computers can store information on several different types of physical media. Magnetic tape, magnetic disk, and optical disk are most common media. Each of these media has its own characteristic and physical organization. Each medium is controlled by a device such as a disk drive or tape drive with its own unique characteristics.

I/O system Management : - One of the purposes of an operating system is to hide the peculiarities of specific hardware devices from the user.

Secondary Storage Management :- Since main memory is too large the computer system must provide a secondary storage to backup main memory. Most modern computer systems use disks as the principle online storage medium, for both programs and data.
The operating system is responsible for the following activities in connection with disk management:
• Free space management
• Storage Allocation
• Disk scheduling

Net working :- A distributed system is a collection of processors that do not share memory, peripheral devices, or a clock. Instead each processor has its own local memory and clock, and processors communicate with one another through various communication lines, such as high speed buses or telephone lines.
The processors in the system are connected through a communication network which can be configured a number of ways. The communication network may be fully or partially connected.