You can add comment lines anywhere in the script to make the code easier to understand.
To add a comment, in the Editor window, put the cursor at the first position of the line that you want to comment (or create a blank line) and type the character ' or type Rem. A comment can be too added at the end of a line using the character ' and then the comment text.
' This is a comment
Rem This is a comment
write("c:\test.txt",a$) ' a comment can be written on the right of a line