Chapter 2 - OS Services

What are the three types of user interfaces?

GUI, Touchscreen, CLI

What devices are used in a GUI?

Mouse, keyboard, desktop interface

What inputs are used in touchscreen interfaces?

Gestures and voice commands

What are the two types of CLI commands?

Internal and External commands

What is a system call?

A request from a program to the OS for service

What is an API?

A set of functions programs use to access OS services

Give examples of APIs.

Win32, POSIX, JVM

Why do we use APIs?

They hide low-level details and standardize behavior

What does the mode bit indicate?

Whether CPU is in user or kernel mode

What are the CPU cycle steps?

Fetch, Decode, Execute, Check Interrupts

What is an interrupt controller?

Manages multiple interrupt sources

What is an interrupt vector?

A number identifying an interrupt source

What is a vector table?

Maps vectors to ISR addresses

What are the steps of handling a hardware interrupt?

Save state, get vector, handle ISR, schedule, restore state

What are faults?

Recoverable software interrupts

What are traps?

Intentional interrupts to enter kernel mode

What are aborts?

Illegal instruction interrupts

How can parameters be passed to system calls?

Registers, Memory, Stack

What are the three types of system calls?

Process control, File management, Communication

What are system programs?

Programs shipped with OS but not in kernel

What is the software stack order?

Applications → System Programs → Libraries → Kernel → Hardware

What is a PCB?

Data structure holding process information

Why are applications OS-specific?

They follow OS ABI rules

What is policy in OS design?

What needs to be done

What is mechanism in OS design?

How it is done

What is a monolithic OS?

Entire OS runs in kernel mode

What is a layered OS?

OS divided into layers

What is a microkernel?

Only essential services in kernel mode

What are OS modules?

Dynamically loaded components

What is a hybrid OS?

Combination of OS designs