91.Int Send message(Int Msg- Void, Int x Mesg):- The integer pointer Msg points to an array of 8 integers , Which is the message Msg void is the identifier of message queue. The message is to be set to a return code of –1 means that the message – Queue – id was not a valid message Queue identifier. A return code of –2 means that they were no available message buffer. In both of these cases the message were not sent.
92.Int Receive Messge(Int Msg-void –id, Int x Msg):- This system calls returns oldest message in the message queue with identifier Msg-Queue-id. If there are no message in the queue the system caller is blocked until a message is sent to the queue. The Msg argument is the addresses of an 8 word array where the message will be placed. A return code of –1 means that the Msg –queue-id was not valid message queue identifier and no message was created.
Disc I/O / Related System Calls
93. Int read disc back(Int block number, char, * buffer):- Disc block block number is read into buffer. The system call always succeeds and returns 0.
94. Int write disk block (int block number, char * buffer):- Disk block block number is read into buffer. It always succeeds & returns zero.
95. Process Management Sub System :- creates the process abstraction. It maintains process tables and message queues, handles system calls and dispatches process to run on processor.
96. Disk driver sub system:- Creates disk abstraction for the user process. It communicates with the disk hardware and handles the disk interrupts. It also includes device driver sub system that accepts the disk operation requests and schedules then on to the disk.
97. OS objects are represented in OS by data structures and implemented with procedures that operate on those data structures.
98. Process States:- 1. Running 2. Ready to run 3. Blocked
99. Process Dispatcher :- It finds a ready process and starts it running.
100. Preemptive Scheduling :- Scheduling is selecting the job and allocating it to the processor. In preemptive scheduling we will not allow a process as long as it likes, but allocates as block of time to it. This block of time is called time slice or quantum.
101. System Stack :- timer Interrupt Handler:- It is called when a timer interrupt occurs. A timer interrupt indicates that the time slice has run out, so the current process has used up its allocation of time now.
102. Timer Interrupt Handler:- It is called when a timer interrupt occurs. A timer interrupt indicates that the time slice has run out, so the current process has used up its allocation of time now.
103. Content Switch :- The saving of content of one process and restoring of content of another process switches the current process and so is called content switch.
104. Context half context switch:- First thing of interrupt hander is save the content of current process is half context switch.
105. Initial Process:- OS causes which creates initially. We assume that there is an initial process that is located at fixed location on disk.
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