Unit 1: Hello world program

We will start our Python journey by creating a programming classic - the "Hello world!" program which simply displays Helo world! on the screen.

Run idle and type the following command and then press Enter:

print("Hello world");

We are using a built-in function print whose job is to display the desired text (in our example Hello world) in the console (a.k.a. shell - a program that understands and carries out Python commands).

Let's create a program that will ask the user for their name and then remember it somewhere, so it can display it afterwards:

name=input("What is your name?");

print(name);

So far, we have been using the shell where you can input one command at a time and then press Enter, after which the line of code gets executed right away. For really simple programs, this is OK, but for longer programs, this may be very unpractical. Therefore, most programmers use a text editor, which allows them to write the program, save it and then run it in its entirety.

To start editing your first Python file, press CTRL+N in the Python shell. This will launch the text editor where you can type multiple commands, one after another, and only when finished with the program in its entirety save it (CTRL+S) and then run it (F5). After I do so, the editor will call the shell and pass on the entire program to it to execute. The output will look something like this:

This is what the entire program looks like in the IDLE text editor:

A shell is a text-based command interpreter that listens to the user's input and then executes the command input by the user. The command can come with parameters. e.g. ipconfig /renew in the Windows PowerShell renews the IP configuration for the machine. ipconfig without any parameters only displays the current IP configuration.

Common shells include:

• Linux shell
• Windows Command Prompt
• Windows PowerShell

Experienced programmers and IT technicians typically work in a shell as opposed to a GUI (graphical user interface).

Here are some interesting Windows Command Prompt commands that work in PowerShell as well:

• tracert URL traces the route it takes to reach a given website
• netstat shows the active TCP connections
• ping URL lets you test the connection to a given URL
• systeminfo displays information about the computer
• net use shows a list of network drives connected to this computer
• driverquery shows all the drivers installed

All commands can be found here.