Creating a Simple Program

In this section, we'll create a simple "Hello World" program consisting of two .pro files. Start the IDLDE and complete the following steps:

Open a new Editor window. Start the IDL Editor by selecting File

New or clicking the New File button on the toolbar.

Create a procedure. Type the following in the IDL Editor window:

PRO hello_main  
   name = ''  
   READ, name, PROMPT='Enter Name: '  
   str = HELLO_WHO(name)  
   PRINT, str  
END

Save the procedure. To save the file, select File

Save or click Save button on the toolbar. Save the file with the name hello_main.pro in the main IDL directory (which the Save As dialog should already show).

Create a function. Open a new Editor window by selecting File

New, and enter the following code:

FUNCTION hello_who, who  
   RETURN, 'Hello ' + who  
END

Save the function. Save the file as hello_who.pro in the main IDL directory. This simple program, consisting of a user-defined procedure, calls a user-defined function.

Compile the programs. Compile hello_main.pro and hello_who.pro programs by selecting Run

Compile All.

Note
You can also type .COMPILE hello_who.pro, hello_main.pro at the IDL command prompt to compile the files. With functions, the compilation order does matter. See Compiling Your Program for details.

Run the program. Select Run

Run hello_main.

Enter a name. Type a name at the IDL command line, which now reads "Enter Name" and press the Enter key. This passes the text to the function hello_who. The "Hello name" string is returned to the procedure and printed in the Output window.