Operating Systems

• Fundamentals

Fundamentals

Processes vs Threads

Main : Processes are executed by threads

Memory

Stack

• Stack allocation called by function
• Each function gets its own memory for local variables
• Freed immediately when function ends
• Too many function calls exceed stack capacity -> stack overflow error (JAVA) / segmentation fault (CPP)

Heap

• Manual deallocation required
• Accessible by multiple threads
• Heap is persistent until program termination
• Memory leak : allocated data is not freed after use
  

File I/O

Concurrency

Scheduling

System Calls

 

Processes vs Threads

• Process: own address space

• Thread: shared address space

• Context switching overhead

• When threads help vs hurt

Memory

• Stack vs heap

• Virtual memory

• Paging vs segmentation

• What a segmentation fault actually is

• Memory leaks and how they happen

File I/O

• File descriptors

• stdin/stdout/stderr

• Blocking vs non-blocking I/O

Concurrency

• Race conditions

• Mutex vs semaphore

• Deadlocks (4 conditions)

Scheduling

• Preemptive vs cooperative

• CPU-bound vs I/O-bound

System calls

• What they are

• Why they exist

• User mode vs kernel mode

Practice explaining out loud

If she asks:

“What happens when a program starts?”

You should mention:

• Executable loaded

• Virtual memory allocated

• Stack/heap setup

• Entry point (main)

• Syscalls for I/O