Process Control Block (PCB) Exam Notes and Quiz

Process Control Block (PCB) Exam Notes

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Process Control Block (PCB): A data structure in the kernel memory that stores all information the operating system (OS) needs about a specific process. Every process has exactly one PCB. It's the "passport" of a process.

Process Table: A data structure that holds the PCBs of all processes currently in the system. Essentially, it's an array or linked list of PCBs.

Process ID (PID): A unique identification number assigned by the OS to each process upon creation. The PCB stores this PID.

The PCB contains all the vital information for managing a process. Key fields include:

• Process State: The current state (New, Ready, Running, Waiting/Blocked, Terminated).
• Process ID (PID): The unique identifier for the process.
• Program Counter (PC): Contains the memory address of the next instruction to be executed.
• CPU Registers: Stores the contents of the processor's registers.
• CPU Scheduling Information: Includes process priority, pointers to scheduling queues, etc.
• Memory-Management Information: Pointers to page tables or segment tables.
• Accounting Information: CPU time used, time limits, user ID, etc.
• I/O Status Information: List of I/O devices and open files.
• Pointer: Pointers for scheduling queues and linking PCBs.

Context Switching ↔️: The PCB is the heart of context switching. The OS saves the context of the current process into its PCB and loads the context of the next process from its PCB.

Interrupt Handling: The PCB stores information needed to handle interrupts and resume the process correctly afterward.

Process Creation: When a process is created, the OS allocates and initializes a new PCB for it.

Location & Security: The PCB is stored in a protected area of kernel memory, inaccessible to user processes to ensure system stability.

Process Table

Advantages ✅

• Centralized tracking.
• Aids in scheduling.
• Simplified management.

Disadvantages ❌

• High memory overhead.
• Can slow down OS.

Process Control Block (PCB)

Advantages ✅

• Enables multitasking.
• Efficient resource management.

Disadvantages ❌

• High memory usage.
• Context switching overhead.
• Security risk if unprotected.

Process Control Blocks and Process Tables Quiz

An interactive quiz on Process Control Blocks and Process Tables!

Why Understand Process Management?

Every modern operating system juggles countless tasks simultaneously. To do this without chaos, the OS relies on two critical data structures: the Process Control Block (PCB) and the Process Table. The PCB is like a passport for a single process, holding all its vital information. The Process Table is the filing cabinet that organizes all these passports.

Understanding these components is fundamental to understanding how operating systems enable efficient multitasking and resource allocation.

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