THE OPERATING SYSTEM MANAGES THE HARDWARE Part (B)- Processes

When a program such as hello runs on a modern system, the operating system provides the illusion that the program is the only one running on the system. The program appears to have exclusive use of both the processor, main memory, and I/O devices. The processor appears to execute the instructions in the program, one after the other, without interruption. And the code and data of the program appear to be the only objects in the system’s memory. These illusions are provided by the notion of a process, one of the most important and successful ideas in computer science. Technical Data about this field explained in computer courses in Rawalpindi.

A process is the operating system’s abstraction for a running program. Multiple processes can run concurrently on the same system, and each process appears to have exclusive use of the hardware. By concurrently, we mean that the instructions of one process are interleaved with the instructions of another process. In most systems, there are more processes to run than there are CPUs to run them. Traditional systems could only execute one program at a time, while newer multi-core processors can execute several programs simultaneously. Some more details of computer courses in rawalpindi are as under.

In either case, a single CPU can appear to execute multiple processes concurrently by having the processor switch among them. The operating system performs this interleaving with a mechanism known as context switching. To simplify the rest of this discussion, we consider only a uniprocessor system containing a single CPU. We will return to the discussion of multiprocessor systems in Section 1.

The operating system keeps track of all the state information that the process needs in order to run. This state, which is known as the context, includes information such as the current values of the PC, the register file, and the contents of main memory. At any point in time, a uniprocessor system can only execute the code for a single process. When the operating system decides to transfer control from the current process to some new process, it performs a context switch by saving the context of the current process, restoring the context of the new process, and then passing control to the new process. The new process picks up exactly where it left off. the basic idea for our example hello scenario.

There are two concurrent processes in our example scenario: the shell process and the hello process. Initially, the shell process is running alone, waiting for input on the command line. When we ask it to run the hello program, the shell carries out our request by invoking a special function known as a system call that passes control to the operating system. The operating system saves the shell’s context, creates a new hello process and its context, and then passes control to the new hello process. After hello terminates, the operating system restores the context of the shell process and passes control back to it, where it waits for the next command line input. TSK is the best institute in Rawalpindi Islamabad for  Pakistani Students who wants to join computer courses in Rawalpindi.