JUST UNIX/LINUX THINGS (Shell,Terminal,Console)

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Anyone who has tried his hands on an Operating System rather than Microsoft and Apple must be familiar with command line interface.So,what we call it? The shell or a console or a terminal?In the linux world they can all look the same from the point of view of the user at the keyboard. The differences are in how they interact with each other.


SHELL:
A Shell provides you with an interface to an OS. It gathers input from you and executes programs based on that input. When a program finishes executing, it displays that program's output. It is a command line interpreter.
Types of Shells:
The Bourne Shell has the following subcategories −
  • Bourne shell (sh)
  • Korn shell (ksh)
  • Bourne Again shell (bash)
  • POSIX shell (sh)
The different C-type shells follow −
  • C shell (csh)
  • TENEX/TOPS C shell (tcsh)


TERMINAL:
A terminal refers to a wrapper program which runs a shell. Decades ago, this was a physical device consisting of little more than a monitor and keyboard. As unix/linux systems added better multiprocessing and windowing systems, this terminal concept was abstracted into software. Now you have programs such as Gnome Terminal which launches a window in a Gnome windowing environment which will run a shell into which you can enter commands.

CONSOLE:

 A console was originally a physical thing, a control panel. In computing terms it usually means the display that you see before the GUI starts up or after it finishes; you can sometimes switch to displaying it instead of the GUI. It's the place where the operating system prints error messages. On a multi-user computer, it's the display that's actually attached to the computer. Just to confuse you, on Windows it can also mean a window with a command shell in it, i.e. a terminal.


A console is generally a terminal in the physical sense that is by some definition the primary terminal directly connected to a machine
 Historically, the console was a single keyboard(Teletypewriter) +CPU and monitor plugged into a dedicated serial console port on a computer used for direct communication at a low level with the operating system. Modern linux systems provide virtual consoles. These are accessed through key combinations (e.g. Alt+F1 or Ctrl+Alt+F1

  • It is physical hardware/interface for writing textual I/O operations
BASIC FUNCTIONALITY IS:

  • The terminal connects to the console where the shell is presented. 
  • The console is like the editor of your program; it helps you in writing but it doesn't really execute anything: when you have finished you send it to the compiler for that.

  • the terminal converts keys into control sequences (e.g. Left → \e[D). The shell converts control sequences into commands (e.g. \e[D → backward-char).the terminal converts keys into control sequences (e.g. Left → \e[D). ]

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