Operating Systems & Parallel Computing

Operating System (OS)

A type of software that manages computer hardware resources and provides common services for computer programs

Device Management

The OS manages all devices connected to a computer (printers, scanners, external hard drives)

Memory Management

The OS manages the memory of a computer, it ensures each program gets the necessary memory to run correctly

Process Management

The OS manages all the processes running on a computer, it ensures each process gets the necessary resources and allows multiple programs to be in memory and run at the same time

Security

The OS provides safety features to protect from viruses/malware

User Interface (UI)

The OS provides a user interface that allows us to interact with the computer and run apps

Kernel Mode

The processor mode that enables software to have full and unrestricted access to the system and its resources

Machine Level

Contains: An instruction set, memory organization (to store data), Input/Output, and a bus structure

Bus Structure

A communication system that transfers data between components inside a computer (or between computers)

Internal Bus

Connects computer internals to the motherboard

Parallel Bus Structure

Multiple bits of data are transmitted simultaneously over multiple channels

Serial Bus Structure

Data is transmitted one bit at a time over a single channel (USB = universal serial bus)

Device Driver

A group of files that enable one or more hardware devices to communicate with the computer’s OS

Resources Managed by OS

Processors, memory, timers, disks, mice, network interfaces

Mainframe OS

Designed to run on large, centralized computers that handle high volumes of data processing and storage

Server OS

Specialized computers that operate within a client/server architecture to serve the requests of client computers on the network

Multiprocessor OS

Used to boost the performance of multiple CPUs within a single computer system

Personal Computer OS

Provide a good interface for a single user, used for word processing, spreadsheets, and internet access

Handheld (Mobile) OS

Designed to run on mobile devices (touchscreens, mobile apps, wireless connectivity)

Embedded OS

Designed to run on embedded systems such as consumer electronics, industrial machines, and automobiles (low power consumption and small memory footprint)

Sensor Node OS

Run on small devices that can sense and transmit data wirelessly (low power consumption, real time processing, wireless connectivity)

Real Time OS

Designed to handle real time applications that require immediate response to external events

Smart Card OS

Run on small plastic cards with embedded sensor microchips, provide secure storage and cryptographic functions

Edit Time

Phase in which source code of a program is written, modified, or reviewed by a programmer

Compile Time

Phase in which source code of a program is translated into machine-readable code by a compiler (object code)

Link Time

Phase in which the object code is linked with other object files and libraries to create an executable file or a shared library

Distribution Time

Phase in which the executable file/shared library is packaged and distributed to end-users or customers (i.e. downloads, media, etc.)

Installation Time

Phase in which the end-user installs the software in their computer

Load Time

Phase in which the OS loads the executable file/shared library into memory and prepares it for execution

Run Time

Phase in which the program is executed by the computer

Thread

A sequence of instructions that can be executed independently by a computer’s CPU

Multithreading

Allows multiple threads of execution to run concurrently on a single CPU

Threadpool

Collection of worker threads that are maintained by the OS and are waiting for tasks to be allocated for concurrent execution by the program

Locking

Mechanism that enforces limits on access to a shared resource when there are many threads, used to ensure that only one thread can access a shared resource at a time

Kernel

The main layer between an OS and the underlying computer hardware, processes memory management, file systems, device control, and network

Scheduler

Component of an OS that manages the allocation of resources and the execution of tasks, ensures each task gets its fair share of resources

Vim

Mode based text editor → You need to enter INSERT mode before you can write text to the file

Nano

Modeless text editor → What you see is what you get command line text editor

ls

List and directories in the current directory

cat

Joins and displays file

touch

Creates an empty file or updates the timestamp of an existing file

mkdir

Creates a new directory

rmdir

Deletes an empty directory

grep

Searches for a pattern in a file or input

traceroute

Traces the route taken by packets over an IP network

ping

Tests the reachability of a host on an IP network

chown

Changes the owner of a file or directory

chmod

Changes the permissions of a file or directory

alias

Creates an alias for a command or sequence of commands

pwd

Prints the current working directory

cd

Changes the current working directory

cp

Copies files and directories from one location to another

rm

Removes files and directories

mv

Moves or renames files and directories

sudo

Executes a command with elevated privileges

echo

Prints text to the terminal or redirects it to a file

vim

A text editor that allows users to create, edit, and view files (V)

nano

A text editor that allows users to create, edit, and view files (N)

which

Displays the location of an executable file in the user’s PATH environment variable

tail

Displays the last few lines of a file or input stream

head

Displays the first few lines of a file or input stream

wc

Counts the number of lines, words, and characters in a file or input stream

find

Searches for files and directories that match specified criteria in a given location

wget

Downloads files from the internet

Race Conditions

When two or more processes are reading/writing some shared data and the final result depends on who runs precisely when

Critical Region

The resource that is being shared between processes

Semaphore

An integer variable that is shared between threads, used to solve the critical section problem and to achieve process synchronization

Binary Semaphore (Mutex)

Can only have two values (0 or 1) and it’s initialized to 1

Counting Semaphore

Its value can range over an unrestricted domain

Beautiful Soup Library

Python library used for pulling data out of HTML and XML files (navigates, searches, and modifies)

/bin

Contains binary executable files

/sbin

Contains binary executable files, used by the system administrator for system maintenance

/etc

Contains configuration files required by all programs and startup/shutdown shell scripts used to start/stop individual programs

/dev

Contains device files

/proc

Contains info about system process

Pseudo File System

Contains info about running processes

Virtual File Systems

Contains info about system resources

/var

Contains variable files

/temp

Directory that contains temporary files created by the system/users

/src

Contains binaries, libraries, documentation, and source code for second level programs

/home

Home directories for all users to store their personal files

/boot

Contains boot loader related files

/lib

Contains library files that support the binaries located under /bin and /sbin

/opt

Contains add on applications from individual vendors

/mnt

Temporary mount directory where sysadmins can mount file systems

/media

Temporary mount directory for removable devices

/srv

Contains server specific services related data

Daemon

Utility programs that run silently in the background to monitor and take care of certain subsystems

Interactive Processes

Run by a user at the command line

Batch Processes

Not associated with the command line and are presented from a list of processes (groups of tasks)

User

The owner of the file (creator by default)

Group

Contains multiple users that have the same permissions access to a file

Other

Any other user who has access to the file

File Permissions

Read (R), write (W), execute (X)

Primary/Log in Group

The group that is assigned to the files that are created by the user

Secondary/Supplementary Group

Used to grant certain privileges to a set of users

Pipe Command

Helps combine two or more commands and are used as input/output concepts in a command (Symbol = |)

Redirecting to a File

When we wish the program’s output to be saved in a file instead of printed to the screen (Symbol = >)

Secure Shell Protocol (SSH)

Cryptographic network protocol for operating network services securely over an unsecured network (client-server architecture)

Function Driver

The one driver in the stack that communicates directly with the device