Example for serial programming

1. Example for serial programming • Loader • Editor • Translator • Debugger

2. Process Or Task • Multiprogramming • Multitasking, Single task os • Multi processing • Multi user system • Multi accessing os • Distributed Os

3. Structure of OS • Kernel – process – create,destroy,suspend • Basic I/O – data blocks – read,write allocate,free. • Memory mgt – segments,pages – read , write , fetch. • File system – Files , devices – create, destroy, open , close , read ,write. • Command language interpreter – Environment data – statements in command language.

4. Types of process • Implicit task • Explicit task • Process relationship • Competition – All process compete with each other for allocation resource needed. • Cooperation – It is exchange data to get the result of explicit tasking.

5. Os view of process • Process descriptor • Process states – scheduled – preempted • Process switch – A transition between two memory resident processes in a multiprogramming is called task switch. • Mode switch • Thread • Scheduling- refers to a set policies and mechanisms built into the os that govern the order in which the work to be done by computer system is completed.

6. OS services for process mgmt • Create (process id ,attributes) • Delete (process id) • Abort(process id) • Fork/join • Suspend(process id) • Resume(process id) • Delay(process id, time)

7. performance criteria • Processor utilization • Throughput • Turnaround time • Waiting time • Response time • Swapping

8. OS concept • System calls • Process table • Fragmentation – refers to the in ability of the os to allocate portion of unused memory. • Partition Description table – current partition status and attributes are st in DS. • Partition allocation strategy – first fit ,best fit worst fit , next fit. • Internal fragmentation-Holes with in the segment.

9. Memory mgmt • External fragmentation(checker boarding)-Holes between the segment. • Coalescing – The process of merging adjacent holes to form a single larger hole. • Compaction or burping the storage or garbage collection • Logical address –The address generated by cpu or pgm . • Physical address – An address seen by the memory unit commonly referred PA.

10. Memory mgmt • Virtual memory – is memory mgt scheme which allows execution of process when only portion of their address spaces are resident in primary memory. • Paging • Page frame • Segmentation

11. Memory mgt • Artificial contiguity – The address contiguous in a process’s virtual address space need not be contiguous in real storage. This is called AC. • Memory map table –The OS keeps track of the status of each page frame by means of a physical memory map that may be structured as a static table.For convenience we refer to this data structure as a memory map table.

12. Memory mgt • Page map table – In paging system address translation is performed with aid of a map table called PMT. • Page fragmentation or page breakage – OS allocates memory in terms of an integral number of page frames .If the size of a given process is not a multiple of the page size , the last page frame may be partially unused . This phenomenon is known as PF. • Pre paging – loading the pages before letting processes run is also called pre paging.

13. Memory mgt • File map table – It is data structure which contains the secondary address of all pages .It mainly used for load missing pages into main memory. • Working set – The set of pages that a process is currently using is called its WS. • Thrashing – A pgm causing page faults every few instruction is said to be thrashing . • Working set model – Many paging system try to keep track of each process working set and make sure that it is in memory before letting the process run . This approach is called WSM.

14. Inter process interaction • Inter process synchronization – a set of protocols and mechanisms used to preserve system integrity and consistency when concurrent processes share resources that are serially reusable. • Inter process signaling – The exchange of timing signals among concurrent process or threads used to coordinate their collective progress.

15. Mutual exclusion • Inter process communication – concurrent cooperating processes must communicate for such purpose as exchanging data , reporting progress and accumulating collective results. • Critical section – is a sequence of instruction with clearly marked beginning and end.

16. Mutual exclusion • Definition: In parallel process a single process temporarily excludes all others from using a shared recourse in order to ensure the system ‘s integrity. • A semaphore - is a protected variable whose value can be accessed and altered only by the two primitive operations ( wait) P and (signal) V. • Binary semaphore – A semaphore whose variable is allowed to take on only the values of 0 (busy) and 1 (free) is called a BS.

17. Mutual exclusion • Counting semaphore – The general semaphore may take any non negative integer value also called CS. • Conditional critical region – allows a process to wait on a condition within a critical section without preventing other eligible processes from accessing the shared resource. • Monitors – are an os structuring mechanism that address this issue in a rigorous and systematic manner.

18. Deadlock • Definition: A process in a multiprogramming system said to be in a state of dead lock if it is waiting for a particular event that will never occur. • Necessary condition: Mutual exclusion, Hold and wait condition, No preemption condition, Circular wait condition

19. Files • Special file: An Os provide an abstraction to allow users to perform I/O without getting buried in all the details of H/W .The abstraction represents each I/O devices as a special file. • Block SF: are used to model devices that consists of a collection of randomly addressable blocks such as disk. • Character SF: consist of character streams, rather than fixed size randomly addressable block. Ex.Terminal, line printer ,network interface.

20. Files • File extension - .bak , .bas , .bin , .ftn , • .hlp , .lib , .man , .tex