Threads vs Processes

A process is a running program with its own memory space.

A thread is a lightweight execution path within a process, sharing memory.

Process vs Thread

Aspect	Process	Thread
Memory	Isolated, own address space	Shared within process
Creation cost	Heavy (new memory, resources)	Light (shares parent's resources)
Communication	IPC (pipes, sockets, shared memory)	Direct memory access
Crash impact	Isolated — other processes unaffected	Can crash entire process
Use case	Isolation, security, stability	Performance, shared state

CPU Clock Speed (Hz)

Hz measures clock cycles per second — not threads or instructions.

A 3.5 GHz CPU executes 3.5 billion clock cycles per second
Each instruction takes 1 or more cycles to complete
A thread runs many instructions, consuming millions of cycles

The Instruction Cycle

Every instruction flows through stages:

Stage	What Happens
Fetch	Get instruction from memory
Decode	Figure out what the instruction means
Execute	Perform the operation (ALU, memory access)
Write-back	Store the result

Pipelining

Modern CPUs overlap stages of different instructions:

Clock:    1     2     3     4     5     6
Inst 1: [Fetch][Decode][Exec][Write]
Inst 2:       [Fetch][Decode][Exec][Write]
Inst 3:             [Fetch][Decode][Exec][Write]

Result: Complete one instruction per cycle once pipeline is full.