Chapter 1 - Introduction

What are the two primary roles of an operating system?

Resource allocator (manages CPU, memory, storage, I/O efficiently) and Control program (controls execution and prevents system-wide crashes).

What three types of management does an OS handle?

Process management, Memory management, and Storage management.

What does an operating system provide to users and applications?

A convenient user interface, system calls, and abstraction of hardware complexity.

Who can be considered a user in a computer system?

A single human, multiple users, or another computer/automated system.

What are system calls and why are they important?

System calls allow applications to request services from the OS while enforcing protection and limiting direct hardware access.

What are the main software layers in a computer system?

Application programs, System programs, OS kernel, and Middleware.

What is the OS kernel?

The core management code that runs in memory with elevated privileges and controls critical system operations.

What are system programs?

Utility programs such as shells, compilers, and editors that support the system and are replaceable.

What hardware components make up a computer system?

CPU, RAM, SSD/HDD, I/O devices, and device controllers connected via a system bus.

What is a device controller?

Hardware that manages a specific device using local buffers and control logic, controlled by device drivers.

How does data move between memory and devices?

The CPU transfers data between main memory and device controller buffers.

What is an interrupt?

A signal that pauses CPU execution to handle an event such as a key press or device completion.

What is an interrupt vector?

A table that tells the system which interrupt handler to execute for each interrupt.

What is a software interrupt?

An interrupt triggered by software when the CPU requires OS handling, commonly used by system calls.

What is user mode?

Execution mode where applications run with limited privileges and restricted hardware access.

What is kernel mode?

Privileged execution mode where the OS performs protected operations after system calls.

What is firmware and what does it do at startup?

Firmware (e.g., BIOS) runs a bootstrap program stored in flash memory that loads the OS kernel.

What are daemons?

Background services that provide system functionality outside the kernel.

How are OS kernels typically driven?

They are interrupt-driven and respond to events by switching modes and executing handlers.

What is process management responsible for?

Creating, deleting, suspending processes, scheduling, IPC, and deadlock prevention.

What does a job scheduler do?

Determines which process runs next on the CPU.

What is caching?

Using small, fast memory to store frequently or predictively accessed data for faster performance.

What is the storage hierarchy?

Organization from fast small storage (registers, RAM) to slower large storage (SSD/HDD).

What does volatile memory mean?

Memory that loses its contents when power is removed.

What is the role of the file system?

Manages non-volatile data stored on secondary storage.

Why are protection and security important in OS design?

They prevent unauthorized access and ensure safe interaction between system components.