OpenEuphoria

Re: Adresses

• Posted by Robert Craig <rds at MSN.COM> Aug 12, 1997
• 846 views

Eduardo Uemura Okada asks:
> Please, I am a very beginner in programming with memory adresses of
> graphic mode 19, can anyone tell me where are the fre memory spaces that
> can be used to place , for example, a virtual screen? Please, if it isn't
> too much, send me the starting and ending adresses, it will be very useful!

Memory for graphics mode 19 starts at #A0000 and there are 200*320 bytes.
Each byte contains an 8-bit color number from 0 to 255.

I think what you are really asking though is: where are the free areas
of memory that you can use for a "virtual" screen. The answer is that
these free areas are not always the same. You must call Euphoria's
allocate() routine (contained in machine.e):

       start = allocate(size)

this will return the starting address of an unused area
of memory containing size bytes. You can store anything
that you like into this memory area. If you say:

   atom virtual_screen

   virtual_screen = allocate(200 * 320)

You will get an address of a block of memory that is
200*320 = 64000 bytes long. You could use this for
storing your virtual screen. You can copy your
entire virtual screen to the "real" screen with:

   mem_copy(#A0000, virtual_screen, 64000)

Regards,
  Rob Craig
  Rapid Deployment Software

P.S. to Jacques: I too have been getting a bounced
mail message from an address on CompuServe lately.
I'm just ignoring it for now.

P.S. to CompuServe members: You can reduce the number of
those silly "=" signs added to your messages by removing
any blanks at the end of each line of your message.
Also, do not send long lines (greater than about
60 characters).