Sytem Components

Process Management
A process is a program in execution
A process needs certain resources, including CPU time,
memory, files, and I/O devices, to accomplish its task
The operating system is responsible for the following
activities in connection with process management
Process creation and deletion
Process suspension and resumption
Provision of mechanisms for:
process synchronizationprocess communication

Main-Memory Management
Memory is a large array of words or bytes, each with its
own address
It is a repository of quickly accessible data shared by the
CPU and I/O devices
Main memory is a volatile storage device. It loses its
contents in the case of system failure
The operating system is responsible for the following
activities in connections with memory management
Keep track of which parts of memory are currently being
used and by whom
Decide which processes to load when memory space
becomes available
Allocate and deallocate memory space as needed

File Management
A file is a collection of related information defined by its creator
Commonly, files represent programs (both source and object forms)
and data
The operating system is responsible for the following activities in
connections with file management:
File creation and deletion
Directory creation and deletion
Support of primitives for manipulating files and directories
Mapping files onto secondary storage
File backup on stable (nonvolatile) storage media

I/O System Management
The I/O system consists of:
A buffer-caching system
A general device-driver interface
Drivers for specific hardware devices

Secondary-Storage Management
Since main memory (primary storage) is volatile and too
small to accommodate all data and programs
permanently, the computer system must provide
secondary storage to back up main memory
Most modern computer systems use disks as the
principle on-line 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

Protection System
Protection refers to a mechanism for controlling access by
programs, processes, or users to both system and user
resources
The protection mechanism must:
distinguish between authorized and unauthorized usage
specify the controls to be imposed
provide a means of enforcement

Command-Interpreter System
Many commands are given to the operating system by control
statements which deal with:

Process creation and management
I/O handling
Secondary-storage management
Main-memory management
File-system access
Protection
Networking

The program that reads and interprets control statements is
called variously:
command-line interpreter
shell (in UNIX)
Its function is to get and execute the next command statement