Operating Systems and How Applications Work

• To run any application OS creates a Process.
• Each Process gets cpu share, Memory and Disk and Network based on the process which you are running.
• Each Process will have unique identifier (id)

Command Line

• Every Command is a computer program/Executable
• Commands have two types of arguments by the way you pass the values
  • positional argument: This argument is processed based on position
    cp 1.txt 2.txt
cp 3.txt 1.txt
  • keyword argument: In this case around the argument you will pass a name or a keyword. Generally linux style name arguments have two hyphens -- if you pass the keyword an single - if you pass the shorthand notation
    ping -c 2 google.com
ping google.com -c 2
ping --count 2 google.com
• Every command line generally has a documentation which we call as manual. Lets start using manual to figure out what commands can do
• When you type any command every operating system has a location where the folders to be searched are configured. This is done by a variable (Environmental variable) called as PATH

Approach to work with commands

• What does the command do.
• Use --help or man <command>
  
• Google <command> examples
  

Concept of user and home directory

• When a user is created in any system a directory called as home directory will be created for the user where he has full permissions
• Tilde ~ on a terminal represents home directory

Windows:  C:\Users\<username>
Linux:  /home/<username>
Mac: /Users/<username>

• In command line dot . represents current directory and double dots .. represent parent directory