[Oberon] On Commands in Oberon.

[Srinivas Nayak]

Dear All,

I have seen and understood how middle mouse button works on a command in 
Oberon.
I have seen commands of the form

Module.Procedure parameter1 parameter2 ~

However, recently I came across some new verities of input parameters. Like
Module.Procedure *
Module.Procedure ^ ~

Also while reading

Programming in Oberon
A derivative of Programming in Modula-2 (1982)
Niklaus Wirth
- a 65 page document briefing the programming in Oberon -

I found that,


    22.4 Standard Input and Output

    The following conventions have established themselves for the
    designation of input texts. Assume that the command
    (procedure) name is followed by
    - an identifier (possibly qualified). Then this is the name of the
    input text (input file),
    - an asterisk (*). Then the marked viewer (window) contains the
    input text,
    - an @ symbol. Then the most recent text selection is the beginning
    of the input text,
    - an arrow (^). Then the most recent selection denotes the file name
    of the input text.


What is the meaning of this, can you please help me understanding this?
How shall we be able to activate commands of the form,

Module.Procedure *
Module.Procedure ^ ~
Module.Procedure @
etc.

With thanks and best regards,

Yours sincerely,
Srinivas Nayak

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Blog: http://srinivas-nayak.blogspot.in/