5. Operating System “ A set of system software routines that sits between the application program and the hardware. ” User Application program Hardware Operating system
6.
7.
8. OS Configuration and Functions OS role Efficient use of resources Consecutive job processing Multiple programming Reduction of the response Improvement of reliability
JCL Function of Job Management is to decode and execute these detailed instructions written in the JCL SPOOL An indispensable function in multi-programming environments Job Scheduling executed by the job scheduler using a dedicated program incorporated in the OS
The buffer provides a waiting station where data can rest while the slower device catches up
Execution Control State Transition Processor becomes free when the process being executed turns into the wait status Execute other process during this time – multiple process (multitasking)
Preemption: Once the time has expired, the processor is interrupted to let another process with the same priority to access the processor. If a second process with higher priority is ready to execute, the OS interrupts the current executing process to the process with higher priority Round robin: Once time is up, execution halted and process is sent to last position in process queue
User process calls on the OS to perform some function requiring privileged instructions. Done by means of a supervisor call (SVC) or system call An interruption occurs An error condition occurs in a user process (program interrupt)
Refer to Text Page 102
Paging Exchange of programs between main storage unit and auxiliary storage device (Refer to Text Page 103 Figure 3-1-18) Address Translation Issue often arises when paging is performed is that the page-in address of the main storage unit is unknown (Refer to Text Page 104 Figure 3-1-19) Segmentation Paging (Refer to Text Page 104 Figure 3-1-20) Page Replacement Least Recently Used (LRU) Method Fist-in First-out) FIFO Method
![Introduction ,[object Object],[object Object],[object Object],[object Object]](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)