Introduction

Program - sits in hard-drive, does nothing, passive entity Process - sits in RAM, actively being loaded and executed

Program vs. Process

Attribute	Program	Process
Nature	Passive entity (file stored on disk)	Active entity (running in memory)
Lifespan	Permanent until deleted	Temporary (created, executed, terminated)
Resource Needs	Only disk storage space	CPU time, RAM, I/O devices, registers
Multiplicity	One program file on disk	Can spawn multiple concurrent processes

Text Segment (Code): Contains the compiled machine code instructions executed by the CPU. This segment is typically read-only to prevent accidental modification.
Data Segment: Holds global and static variables.
- Initialized Data: Variables explicitly initialized in code (e.g., int x = 10;).
- Uninitialized Data (BSS): Global/static variables initialized to zero by default.
Heap: Dynamically allocated memory at runtime (e.g., using malloc() in C or new in C++/Java). The heap grows upward toward higher memory addresses.
Stack: Temporary storage for function calls, local variables, parameter passing, and return addresses. The stack grows downward toward lower memory addresses.

This contains all details about the process. This is like a blueprint.

Process ID (PID): A unique identifier assigned to the process.
Process State: Current state (e.g., Ready, Running, Waiting).
Program Counter (PC): Points to the address of the next instruction to execute.
CPU Registers: Saved register contents when the process is context-switched out.
CPU Scheduling Info: Priority level, scheduling queue pointers, and accounting stats.
Memory Management Info: Page tables or segment tables for mapping virtual to physical memory.
I/O Status & Open Files: List of open file descriptors and allocated I/O devices.

new, ready, running, terminated are self explanatory.
waiting happens when the process request some user input, hard-disk read, or waiting for another process to complete (join concept at the end of main thread)