CSC 4103- Midterm Flashcards (CH.1)

What are the four components of a computer system

Hardware, Operating System, Application programs, Users

Hardware

provides basic computing resources, like CPU, memory, I/O devices, graphics card, and storage

Operating Systems

A program that acts as a “middle-man” between a user and the computer hardware. Manages hardware resources and provides services to apps

Application programs

Defines how the system resources are used to solve the computing problems of the users (includes, web browsers, office apps, video games, etc basically any app)

Users

Whoever utilizes the computer (people, machines, other computers)

What is the hierarchy of a computer system?

hardware → OS → application programs → users

Goals of an operating system

1. Execute user program and make solving problem easy

2. Using the computer hardware in efficient manner

3. Make the computer system convenient to use

Device Controller

An electronic hardware component (like a chip or circuit board) that acts as a translator and bridge between a computer’s OS and a physical peripheral device like a mouse or keyboard

Resource allocator (OS)

An operating system that mamnges all resources and decides between conflicting request based on effieceint and fair resource use (tradeoff)

Control Program (OS)

AN OS that controls the execution of programs to prevent errors (reliability) and improper use (security) of the computer. It also controls and manages operations of hardware I/O devices

OS kernel

The one program running at all times on the computer

Computer- system organization

one or more CPUs and/or device controllers connected through a common bus providing access to a shared memory

The bootstrap program

Loaded at power-up/startup or reboot. AKA firmware (software stored in a chip that can be updated) that is typically stored in ROM or EPROM. It initializes all aspects of the system from hardware to software, loads OS kernel and starts execution

Interrupts

A signal sent to the CPU by hardware or software that temporaily pauses the currently running program so the operating system can handle an event without continuous polling (constant monitoring).

Interrupt handling

1. The OS preserves the state of the CPU by storing registers and the program counter

2. interrupt transfers control to the interrupt service routine through the interrupt vector

3. Int. arch. must save the addr. of the interrupted instruction

4. After completing the int. the state and return addr. are restored

Why is disabling interrupts a priviledged instruction?

Because allowing user programs to disable interrupts could prevent the OS from responding to events and regaining control of the CPU

Synchronous I/O

Control returns to the user program (or other OS code) only upon I/O completion and wait instruction idles the CPU until the next interrupt

Asynchronous I/O

Control returns to to user program without waiting for I/O completion

Storage Structure

1. Main memory

2. Secondary storage

   1. hard disks

   2. solid-state disks

Main memory

only large storage media that the CPU can access directly (RAM, volatile, byte-addressable, fast, small)

Secondary storage

Extension of main memory that provides large storage capacity (block access, nonvolatile, slow, big)

can be either hard or solid-state disks

Hard Disks

rigid metal or glass platters covered with magnetic recording material. The disk controller determines the logical interaction between the device and the computer

Solid-state disks

faster than hard disks and are nonvolatile

Caching

Stores copies of frequently accessed data so the CPU doesn’t have to retrieve them from slower memory. If the requested data is already in the cache it is called a hit if not it is called a miss and must be retrieved from a lower storage

Registers

Tiny, extremely fast storage locations inside the CPU that hold values the CPU is actively working with. it temporaily holds data, instructions, or memory addresses the processor is actively using

Mulitprocessor systems

AKA parallel systems or tightly coupled systems. Its more than one CPU or processor in close communcation

Advantages of a parallel system

1. increased throughput

2. economy of scale

3. increased reliability

Symmetric multiprocessing (SMP)

Each processor runs an identical copy of the OS

Asymmetric multiprocessing

Each processor is assigned a specfic task; master processor schedules and allocates work to slave processors

Clustered Systems

Multiple systems (nodes) working together usually sharing storage via a storage-area network (SAN), provides a hih-availibilty service which survives failures. Some are high-performance computing (HPC) and application must be written to use parallelization

Asymmetric clustering

has one machiene in hot-standby mode

Symmetric clustering

has mulitple nodes running applications and monitoring each other

Operating system structure

1. multiprogramming

2. timesharing (multitasking)

multiprogramming

Multiple programs are loaded into the memory at the same time (jobs) so that the CPU can execute them concurrently. When one program waits for the I/O the OS switches the CPU to another ready program

Timesharing

(AKA multitasking) CPU switches jobs so frequently that users can interact with each job while its running (interactive computing)

Different modes of an OS

1. Dual-mode

2. User mode

3. kernel mode

Dual mode

The safety system in a computer’s processor that let’s it switch between two different levels of software priviledges and protects the OS and hardware by preventing user programs from executing priviledged instructions.

User mode

Restricted running state where regular apps (EX. web browsers, games, etc) execute. The program cannot directly touch the computer’s hardware or crash the whole system. Can only request hardware realted operations through system calls

Kernel mode

A fully privledged running state where the core of the OS lives and runs. SOftware has complete unrestricted access to the hardware, memory, and CPU instructions.

Process

a program in execution, an active entity

What is the OS in connection with the process management responsible for

1. Creating and deleting both user an system process

2. suspending and resuming processes

3. providing mechanisms for process synching

4. providing mechanisms for process communication

5. providing mechanisms for deadlock handling

Communation models

1. Message passing model: info is exchanged through interprocess communication facility provided by OS

2. Shared memory model: processes use map memory sys. calls to gain access to regions of memory owned by other processes

Memory managment

Determines what is in memory and when optimizing CPU utilization and computer responses to users.

1. tracks which part of memory are currently being used and by whom

2. decides which process and data get to move into and out of memory

3. allocating and deallocating memory space as needed

Direct Memory Access (DMA)

Allows hardware devices to transfer data directly to and from the computers main memory RAM without making the CPU handle every single byte

Cache consistency

In order to maintain consistency data is stored in more than one level, the copy of the specfic data appears in several places (Ex. nagnetic diskm main memory, in the cache, and internal registers)

Cache coherency

Update of a copy of data need to be in all caches where the data resides

I/O subsystem

The part of the OS that mangees communication between computer and it’s I/O devices (Ex. keyboards, disks, printers, etc)

responsible for:

1. memory management for I/O

   1. Buffering

   2. caching

   3. spooling

2. general device-driver interface

3. drivers for specfic hardware devices

Buffering

storing data temporaily while it is being transferred

Spooling

the overlapping of output of one job with input of other jobs

Protection

any mechanism for controlling access of processes or users to resource defined by the OS

Security

Defense of the system against internal and external attacks

Computing Environments

The combination of hardware, software, networks, and services that provide the framework and interface for computer programs to run and users to interact with the system

Distributed computing

A collection of seperate, possibly heterogenous, systems networked together (EX. LAN, WAN, MAN, etc)

Network operating system

provides features between systems across a network

Client-server

Clients processes request services or resources and the server processes fulfill those request by providing data, hardware access, or computation

also uses Computer-server system (provides interface to client to request services) and file-server system (interface for clients to store and retrieve files)

Peer-to-peer

All nodes are considered peers (no distinguishing between clients and servers) and can either act as a client, server, or both

Virutalization

Allows operating systems to run apps in other OSes through Emulation, and dividing a single physical computer into isolated virtual machienes (VMs)

Cloud computing

Delivers computing, storage, even apps as a service across a network or a “cloud”

1. public cloud (available via internet to anyone willing to pay)

2. private cloud (ran by a company for the company)

3. Hybrid cloud (includes both oublic and private cloud components)

Software as a service (SaaS)

one or more apps available via the internet

Platform as a service (PaaS)

Software stack ready for apps use via the internet

Infrastructure as a service (IaaS)

servers or storage available over the internet

Open-source operating systems

OSes made available in an source-code format rather than just binary (closed-source) and was the direct counter to the copy protection and digital rights managment (DRM) movement

Timer

Used to prevent infinite loops therby protecting the CPU