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The Terminal in UNIX
By: Gabor Bernat
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    Table of Contents:
  • The Terminal in UNIX
  • Speed it up
  • A work session
  • Basic concepts for working with the shell



    The Terminal in UNIX

    (Page 1 of 4 )

    When we're talking with someone who does not speak our language, it's good to have a translator around to avoid any misunderstandings. If you don't have someone who can translate directly between both languages, having two translators (with an intermediate language they both share) may do the job. When we are communicating with computers, the situation is the same; only the terms change.

    Say we have you and a computer device trying to communicate. You know what you want to do; however, you want to tell this to the computer. It's quite complicated to "talk” with the device itself (because each of them boast so many details, you must pay attention). Therefore, in order to simplify this, operating systems were created. 

    Still, the operating system has a language of its own, which you now need to learn. Although it is now much simpler to tell a device what you want, it is still a troublesome job. Therefore, in order to make your life easier, a new translator has appeared; this is the shell. The shell will communicate with the kernel, as I explained in the previous article entitled "Operating Systems and UNIX."

    You can converse with the shell via the terminal. You can start the terminal from the Accessories-> Terminal if you use GNOME. This simulates an input/output device into which you can enter only text, and you will get back only text. Today most operating systems built on UNIX come with a graphic interface. However, there was a time when this was not true. 

    Initially, in the 1970s, the input device was a teletypewriter. That is why the name of the special file that connects the terminal is called tty.TTY. Communication took place through a serial port, where you could type in the information and the answer would come back via print on a page. At the end of 1970s, CRTs arrived, especially via Dell's VT series.

    Here the text contained 80 columns and 24 lines. Early on, the interface could only print text on the screen. The graphical interface evolved later and made it possible to draw a picture on the screen. Now the terminal was just emulated to draw the input and output character sequences to the screen. The programs that achieve this task emulate terminals.

    As time elapsed and personal computers added a keyboard and a mouse, there was no longer a need for a concrete input device to enter the data (like the serial port) and the operating system itself opened two files through which to carry out communication. These are the pseudo terminals.

    Today we will learn how to use the pseudo terminals at a basic level. To really absorb the material in this article, you will need to practice with a real pseudo terminal, so you will need to have a UNIX-based operating system installed on your computer. I will use the Linux distribution named Ubuntu. If you are doing the same, you can start via the Accessories -> Terminal route.

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