3. a. How many Process Control Blocks (PCB) would you expect while running your

Question

3. a. How many Process Control Blocks (PCB) would you expect while running your OS?(Briefly, why)?   

b. Is a PCB part of a device controller, a file, or something else (what)?   

c. Describe three pieces of information in a Process Control Block (PCB).

4. Windows mostly supports “backwards compatibility” in the OS, MACs usually don’t.Considering application programs, what is backwards compatibility? Does this also mean that a 20 year old graphics controller works on a new Windows PC?      (please, briefly explain)

Explanation / Answer

3 a)

In any operating system a process is identified by Process ID (PID). An operating system runs many processes each having their own PID. Most of the operating system supports multi programming, so it needs to keep track of all the processes. To manage this Process Control Block (PCB) is used to track the process execution state. In any operating system-

3 b)

PCB is the area stored in memory to keep track of the individual process. It contains information about the process, i.e. registers, quantum and priority. The PCBs are connected via a process table which logically contains the PCB for all the current processes in the system.

3 c)

A PCB typically contains many information about the process. A typical process control block contains the following information:

Pointer: It keeps track of the switching state of the pointer. It is a stack pointer which is required to be saved when the process is switched from one state to another state in order to retain the current position of the process.

Process State: This stores the current state of the process.

Process Number: Every process is assigned with a unique id known as Process number which stores the information about identifier.

Program Counter: This stores a counter which contains the address of the next instruction to be executed for that process.

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