Week 1 - OS and Linux intro Flashcards
What are the 4 fundamental tasks of a computer?
Input
Process
Output
Store
Explain IPOS Cycle
Input - from user informs computer (program) what to do
Processing - converts data to information
Output - information output so user can view results
Storage - Results can be stored for permanent record
Central Processing Unit (CPU)
Performs the fetch-execute cycle
Fetch next program instruction from
memory
Decode the instruction into actions
Command the relevant part(s) of the
computer to operate to execute the
instruction
Store the result somewhere (if necessary)
What does the CPU consist of?
Control Unit
Handles the fetch execute cycle
Controls the other components of the computer through
signals
Contains registers for important pieces of information like
the memory location of the next instruction
Arithmetic Logic Unit (ALU)
Digital circuits to perform arithmetic and logic operations
Data registers to store data being used by the current set
of instructions
Registers
Data Registers
Program Counter - store location of next program instruction in memory
Instruction Register – store current instruction
Status Flags – store information about last operation
Stack Pointer – store location of the top of the runtime stack where we store information about the
program’s currently executing function
Types of memory from fastest to slowest?
Registers (SRAM)
Cache (on-chip and off-chip), (SRAM)
Main Memory (SRAM)
Secondary storage (hard-disk, optical disk, flash memory)
What is software?
Software are the programs that the computer
runs
– Without software, the computer does
nothing
What is a program?
A program is a step-by-step description of how to perform a task, written in a language the computer can execute
– Machine language
We write programs in easier languages like C++ or Java and convert them into machine
language using a program called a compiler
Input and output devices examples
Input - keyboard, mouse, mic
Output - Monitor, printer, speakers
What is an Operating system?
helps to mediate access to various computer resources, including the CPU, memory, and I/O (input/output) devices.
In other words, the operating system manages the use of these resources by different programs or applications running on the computer.
CPU - which program gets allocated to processor
Memory - What memory can each program use and what to do when memory has ran out - hierarchy.
I/O Devices - Allocated requests from programs for I/O actions and abstracts details of how to interface with device
The operating system is …?
A program that manages hardware and software and is comprised of many components, some loaded into memory and some only loaded when needed.
Core component is the Kernel
What tasks does OS handle?
The OS handles such tasks as
– Process management
– Memory management
– Input/output
– User interface
What is a kernel?
Resource Manager
– Processes
– Memory
Everything Linux DOES is a process
Process: program the kernel launches into memory to do a task
core of Linux OS
Once user initiates a request what happens?
The user does not control computer hardware
The user initiates requests then the OS decides if the user has adequate access rights to perform the requested actions and how to
carry out those actions.
The kernel handles most of the significant operations.
The user interface can be tailored, known as a shell.
Communication with devices is handled through device drivers.
What layers is a computer segmented into?
– User at the top
– Hardware at the bottom
– Application software and operating system components make up intermediate layers
Describe main functions of Kernel
Processes: Determines which processes are allowed to use the CPU
Memory: Keep track of memory – what memory is allocated to each process, what memory is free
Device Drivers: Interface between hardware (e.g disk and I/O) and processes
System Calls: Processes use system calls to
communication with Kernel
Linux Advantages?
Open Source
96.3% of world’s top 1 million servers use Linux
Greater control
Viruses are non-existent
Linux command line
Part of a shell
The shell includes
- command line interface (CLI) which is the command line and prompt
- Any previously defined entities
- functions
- aliases
- variables
- previous instructions as part of a history
list - The shell’s interpreter
Linux Interpreter
> Its responsibility is to interpret
instructions
> By interpreting, it translates each
instruction on the command line into an
executable statement
> Interpreters are found in many
programming languages (e.g., Python,
Ruby, LISP)
> Interpreters are used in most CLIs
Linux The Shell
The shell is a customizable environment
– The environment consists of previously defined
terms and instructions
– The shell allows you to define shortcuts in
executing future instructions
– Different Linux shells have different features
Advantages of Linux GUI
– Less to learn and easier to
control
– Intuitive
– Visual
– Fun
– Allows for easy
multitasking
Advantages of CLI
– Control
– Speed
– Less resource intensive
– Limits wrist strain
– You learn more about the
OS through the CLI
Virtual Machines
- VM is an emulation of a particular computer
system
Virtual machine
– Software running on your computer emulating
another platform
– The VM is a combination of the software and data
that captures the other platform’s operating system
Linux Distro
A Linux distribution, or “distro”, is a customized version of the Linux operating system that includes specific software applications, configurations, and user interfaces. Linux distros are created by groups of developers and organizations, and can be tailored to suit various use cases such as desktop computing, servers, and embedded devices. Linux distros are known for their security, stability, and customizability, and are often free and open-source.
Linux file system
– The way files are stored and
organized to simplify access to
data
Logical File System: Users View
of File System
– Abstraction over physical file
system
– Files, Directories, Partitions
Physical File System: Devices
and methods to store physically
store data (e.g. Magnetic Disk)
– Blocks, disk surface, file pointers,
read write arm etc
Linux primary storage
– Physical medium where files
are stored
– Internal Hard Drive
Linux directory structure
Linux has only one root directory
– All files and subdirectories are placed under the
root directory in a treelike structure
Filesystem Hierarchy
Standard (FHS)
Specifies requirements and
guidelines for file and
directory placement in UNIXlike operating systems
Partition
Logical division of collection of storage into independent units
Directory
User specified location that allows a user to organise files
File
Basic unit of storage, will store data or an executable program
File path
– A description of how to reach a particular file or
directory
– Absolute Path: starts at the root (/)
– Relative Path: starts at the current working directory
Linux servers
NO graphical environment
– Administrators need to learn how to navigate
using Command Line Interface only
BASH
- BASH is Unix/Linux Shell software
- Default Shell for almost all Linux Distros
- Uses BASH command syntax
Commands:
– pwd displays current directory
– cd changes directory
– ls lists contents of a directory
– man shows help files
– mkdir creates a directory
– rm removes a file or directory
- rmdir removes empty directories
– mv moves and renames files
– cp copies files
– ln makes hard and symbolic links
– su changes the current user temporarily
- touch creates a new empty files and updates the timestamp of an existing file
Wildcards
– Represents any letter (or sequence of letters) used
to specify a filename or path
– Linux administrators use wildcards to:
* Navigate to directories faster
* Move or delete a group of files
* Locate files based on a portion of their filenames
Wilcards *
represents zero or more characters
Wildcards ?
represents only one character
