Below is a complete, detailed study guide covering all topics from Part 4 of your Unix course on Process Management. This guide explains every concept—from definitions and process attributes to creation, state transitions, and termination—with code snippets (where applicable) and thorough explanations. Use this guide as your sole study resource to prepare for your exam.

1. Overview of Process Management

Definition of a Process:

• A process is an instance of a program in execution. In other words, it represents a task currently being executed by the operating system.
• Processes are the basic units of work managed by the OS.

Key Points:

• When a program runs, the operating system creates a process.
• Processes allow multitasking by executing several tasks concurrently.

2. Process Identification and Attributes

Every process in Unix is characterized by several attributes that help the system manage it effectively:

• PID (Process Identifier):

  A unique numerical value that identifies a process.

  Example: The first process started by the system (typically the init process) has a PID of 1.

• PPID (Parent Process Identifier):

  The PID of the process’s parent (the process that created it).

  Note: Every child process holds the PPID of its parent.

• UID (User Identifier) and GID (Group Identifier):

  These identify the user and the group that initiated (or owns) the process. They help in enforcing permissions and access rights.

Hierarchy Example:

• init (PID: 1): The very first process launched by the kernel after boot. It is the ancestor of all other processes.
• login (PID: 12, PPID: 1): A child process of init that handles user authentication.
• bash (PID: 172, PPID: 12): The command shell started after a successful login.
• gedit (PID: 558, PPID: 172): An application (e.g., a text editor) launched from the shell.