CS 241 - Operating System: Process Concept

Process Execution Requirements

• A process requires a unique identifier (PID) and allocated memory to execute.
• Memory layout includes various sections: code, stack, heap, and data.

Purpose of Stack in Memory Layout

• The stack is used for function call management, including local variables and return addresses.
• Supports Last In, First Out (LIFO) operation, allowing orderly function execution and exits.

Difference Between Program and Process

• A program is a static set of instructions stored on disk; a process is an active execution of a program.
• Multiple processes can run the same program concurrently.

Purpose of the Data Section

• The data section stores global and static variables that are initialized prior to execution.
• Divided into initialized and uninitialized data segments for memory management.

Role of the Program Counter

• The program counter keeps track of the next instruction to be executed in a process.
• It is essential for the flow of execution and maintaining order in instruction processing.

Initialized vs. Uninitialized Data Sections

• Initialized data section contains variables with defined initial values.
• Uninitialized data section holds variables set to zero or undefined until assigned.

Maximum Processes Associated with a Link

• A link can associate a maximum of 256 processes, depending on system limitations.

Non-Blocking Send Operations

• After sending a message, the sender does not wait for the receiver to acknowledge receipt.
• This allows the sender to continue executing other tasks immediately.

Characteristic of a Zero-Capacity Buffer

• A zero-capacity buffer does not store any messages; it requires the sender and receiver to be synchronized.

Blocking Send and Receive

• Blocking send occurs when the sender waits for the receiver's acknowledgment.
• Blocking receive waits for a message to be sent before proceeding with execution.

Characteristic of an Unbounded Capacity Buffer

• An unbounded buffer can grow in size infinitely, accommodating as many messages as needed.

Limitation of Ordinary Pipes

• Ordinary pipes provide unidirectional communication and require a direct parent-child process relationship.

Process Control Block (PCB) Information

• A PCB stores process state, PID, program counter, CPU registers, memory management information, and I/O status.

Purpose of 'long state' in Task Struct

• The 'long state' field indicates the current status of a process (e.g., running, waiting, or stopped).

Data Structure for Active Processes in Linux

• A task struct represents all active processes, linking their PCBs for process management.

Process-Parent Relationship

• Each process has a parent process that creates it, establishing a hierarchical relationship in process management.

Purpose of 'pid' Field in Task Struct

• The 'pid' field uniquely identifies each process in the system, crucial for process control and management.

Term for Child Process

• A process created by another process is referred to as a child process.

Primary Goal of Process Scheduler

• The process scheduler aims to optimize CPU utilization, fairness, and response time among processes.

Data Structure for Ready Queue

• A queue, often a linked list or array, organizes processes ready for execution by the CPU.

I/O Request Process Behavior

• When a process issues an I/O request, it moves from a running state to a blocked state until the operation completes.

Trigger for Process to Leave CPU

• A process is removed from the CPU when it is preempted by a higher-priority process or issues an I/O request.

Process Status in Wait Queue

• A process in the wait queue is in a blocked state, waiting for a specific event or resource to proceed.

Initial Placement of New Processes

• New processes are initially placed in a ready queue, awaiting CPU time for execution.

Named Pipes vs. Ordinary Pipes

• Named pipes support bidirectional communication and can be accessed by unrelated processes, unlike ordinary pipes.

Purpose of Sockets in Networked Systems

• Sockets facilitate communication between processes over networks, enabling data exchange between different systems.

Function of Stub in Remote Procedure Call

• A stub acts as a proxy for remote procedure calls, handling communication between the client and server.

Significance of IP Address 127.0.0.1

• The IP address 127.0.0.1, known as localhost, allows a device to communicate with itself for testing.

Difference Between Sockets and Pipes

• Sockets provide network communication capabilities, while pipes are used for inter-process communication within the same system.

Purpose of Port Numbers in Socket Communication

• Port numbers identify specific processes or services on a device, enabling targeted communication over a network.