OS101MOD1

• Operating System is a collection of software

  that manages computer hardware resources and

  provides common services for computer programs.
• Operating System is an interface between a computer user

  and computer hardware.
• Memory management refers to management of Primary Memory or Main Memory. Main

  memory is a large array of words or bytes where each word or byte has its own address.
• Main memory provides a fast storage that can be accessed directly by the CPU. For a program

  to be executed, it must in the main memory.
• An Operating System does the following activities

  for memory management

  Keeps tracks of primary memory, In multiprogramming, the OS decides which process will get memory when and

  how much, Allocates the memory when a process requests it to do so, De-allocates the memory when a process no longer needs it or has been

  terminated.
• In multiprogramming environment, the OS decides which process gets

  the processor when and for how much time. This function is

  called process scheduling.
• An Operating System does the following

  activities for processor management −

  Keeps tracks of processor and status of process. The program

  responsible for this task is known as traffic controller.

  Allocates the processor (CPU) to a process.

  De-allocates processor when a process is no longer required.
• An Operating System manages device communication via their

  respective drivers. It does the following activities for device

  management −

  Keeps tracks of all devices. Program responsible for this task is

  known as the I/O controller.

  Decides which process gets the device when and for how much

  time.

  Allocates the device in the efficient way.

  De-allocates devices.
• A file system is normally organized into directories for easy navigation

  and usage. These directories may contain files and other directions.
• An Operating System does the following activities for file management

  Keeps track of information, location, uses, status etc. The collective

  facilities are often known as file system.

  Decides who gets the resources.

  Allocates the resources.

  De-allocates the resources.
• Security − By means of password and similar other techniques, it prevents

  unauthorized access to programs and data.
• Control over system performance − Recording delays between request for a

  service and response from the system.
• Job accounting − Keeping track of time and resources used by various jobs and

  users.
• Error detecting aids − Production of dumps, traces, error messages, and other

  debugging and error detecting aids
• Coordination between other software’s and users − Coordination and assignment

  of compilers, interpreters, assemblers and other software to the various users of

  the computer systems.