Operating Systems Flashcards

Flashcards on Operating Systems

Operating System

A program that acts as an intermediary between computer users and computer hardware.

Goals of an Operating System

Execute user programs and make solving user problems easier; Make the computer system convenient to use; Use the computer hardware in an efficient manner.

Hardware

CPU, memory, I/O devices

Operating System (Component)

Controls and coordinates use of hardware among various applications and users.

Applications

Define ways in which the system resources are used to solve user problems (e.g., browsers, games).

Users

People or other systems that interact with the computer system.

Operating System as a Resource Allocator

Manages all resources and decides between conflicting requests for efficient and fair resource use.

Operating System as a Control Program

Controls execution of programs to prevent errors and improper use of computer.

Kernel

The one program running at all times on the computer.

Bootstrap Program

Loaded at power-up or reboot and initializes all aspects of the system; typically stored in ROM or EPROM (firmware).

BIOS

Basic Input/Output System, used in older PCs for computer startup.

UEFI

Unified Extensible Firmware Interface, used in modern systems for computer startup.

Computer System Organization

Connects CPUs and device controllers through a common bus, providing access to shared memory.

Device Controller

In charge of a particular device type and has a local buffer.

Interrupt

A signal sent to the CPU to pause its current task and handle an urgent event.

Hardware Interrupts

Generated by devices (e.g., printer finishes a job).

Software Interrupts (Traps/Exceptions)

Generated by programs (e.g., division by zero, system calls).

Interrupt Vector

Contains the addresses of all Interrupt Service Routines (ISRs).

Blocking I/O

CPU sends I/O request and waits; CPU does nothing until I/O is done.

Non-Blocking I/O (Asynchronous)

Control returns to program after I/O starts; CPU gets interrupted when I/O is done.

Device-Status Table

Tracks each device’s type, address, and state; used by the OS to manage I/O devices.

Dual Mode Operation

CPU has a mode bit (0 = kernel mode, 1 = user mode) to restrict dangerous actions.

User Mode

Restricted access (e.g., can’t directly read/write hardware).

Kernel Mode

Full control over hardware (e.g., managing memory, devices).

Main Memory (RAM)

Direct CPU Access, but volatile (loses data when power is off)

Secondary Storage (HDD/SSD)

Non-volatile – data persists even when power is off.

Speed vs. Cost in Storage Hierarchy

Faster storage is more expensive per GB.

Caching

Copy frequently used data up the storage hierarchy.

Device Drivers

Uniform interface between OS and hardware.

Cache

Small, ultra-fast memory storing frequently used data.

Cache Hit

Data found in cache (no RAM trip needed!).

Cache Miss

Data fetched from RAM.

Symmetric Multiprocessing

Multiple CPUs share the system bus and memory.

Clustered Systems

Multiple systems working together, usually sharing storage.

Multiprogramming

Organizes jobs so CPU always has one to execute.

Timesharing (Multitasking)

CPU switches jobs so frequently that users can interact with each job while it is running.

Process

A program in execution.

Single-Threaded Process

Single program counter specifying location of next instruction to execute.

Multi-Threaded Process

One program counter per thread.

Memory Management

What is in memory and when; optimizes CPU utilization and computer response to users.

Storage Management

Abstracts physical properties to logical storage unit - file.

Mass-Storage Management

Used to store data that does not fit in main memory or data that must be kept for a long period of time.

Protection

Any mechanism for controlling access of processes or users to resources defined by the OS.

Security

Defense of the system against internal and external attacks.

Singly Linked List

Data structure where each node points to the next node in the sequence.

Doubly Linked List

Data structure where each node points to both the next and previous nodes in the sequence.

Network Computers

Thin clients that provide web access to internal systems.

Mobile Computers

Use IEEE 802.11 wireless or cellular data networks for connectivity.

Distributed Computing

Collection of separate, possibly heterogeneous, systems networked together.

Network

A communications path (TCP/IP most common).

Network Operating System

Provides features between systems across network (communication scheme allows systems to exchange messages).

Compute-Server System

Provides interface to client to request services (i.e., database).

File-Server System

Provides interface for clients to store and retrieve files.

Peer-to-Peer Computing

All nodes are considered peers and may each act as client, server, or both.

Virtualization

Allows operating systems to run applications within other OSes.

Emulation

Source CPU type is different from target type.

Virtualization

OS natively compiled for CPU, running guest OSes also natively compiled.

Cloud Computing

Delivers computing, storage, even apps as a service across a network.

Public Cloud

Available via Internet to anyone willing to pay.

Private Cloud

Run by a company for the company’s own use.

Hybrid Cloud

Includes both public and private cloud components.

Software as a Service (SaaS)

One or more applications available via the Internet (i.e., word processor).

Platform as a Service (PaaS)

Software stack ready for application use via the Internet (i.e., a database server).

Infrastructure as a Service (IaaS)

Servers or storage available over Internet (i.e., storage available for backup use).

Real-Time OS

Has well-defined fixed time constraints (processing must be done within constraint).

Open-Source Operating Systems

Operating systems made available in source-code format rather than just binary closed-source.