Action! : Compute Free Memory?

[+Ripdubski]

Whats the best way to determine the amount of free memory in Action!?

RAMTOP - MEMLO ?

 

CARD RAMTOP=106
CARD MEMLO=743

MODULE 

PROC Main()
CARD dT,dL,dF

dT=RAMTOP*256
dL=MEMLO
dF=dT-dL

PrintF("%EFrom:%E")
PrintF("RAMTOP=%B%E",RAMTOP)
PrintF("Top=%U (%H)%E", dT, dT)
PrintF("Bot=%U (%H)%E", dL, dL)
PrintF("Fre=%U (%H)%E", dF, dF)

PrintF("%EReserving 1K...%E")
RAMTOP==-4

dT=RAMTOP*256
dL=MEMLO
dF=dT-dL

PrintF("%ETo:%E")
PrintF("RAMTOP=%B%E",RAMTOP)
PrintF("Top=%U (%H)%E", dT, dT)
PrintF("Bot=%U (%H)%E", dL, dL)
PrintF("Fre=%U (%H)%E", dF, dF)

RETURN

 

[Rybags]

No.  RAMTOP is set by the OS to be the first non RAM page, then the screen will open immediately below it.

 

MEMTOP (2E5, 2E6) is maintained by the OS and will point to the address just below the Display List which should be the top of free RAM.

 

MEMLO is also wrong, it's the first free location once the OS has started then updated if a Dos or handler reserving memory is booted.

 

APPMHI (E,F) is maintained by language processors as the highest location in use (+1) - the OS refers to it when opening a screen to ensure memory corruption doesn't occur.

 

So, to deduce free RAM you'd subtract the value held in APPMHI from that in MEMTOP.

[zbyti]

Allocaling free memory

Quote

There isn't a function in Action! that approximates BASIC's FRE(0) command. It isn't as simple as checking the monitor to see where the end of your program is, because Action! tries to help you out by placing some non-initialized arrays beyond the end of your program code, instead of inside your program, where they're declared (specifically, CARD ARRAYs and, generally, BYTE ARRAYs over a page in length).

 

Luckily, there's an easy method for determining where the end of the program and variable space actually is. The first CARD ARRAY declared in a program is the last actually allocated during compilation.

MODULE ; Sample 1

CARD
  MEMT0P=$2E5, freemem=[0]
CARD ARRAY
  EndOfProgram(1)

PROC Main()
  freemem=MEMTOP - EndOfProgram
  PrintF("Total free memory=%U%E", 
             freemem)
RETURN

 

Edited January 23, 2021 by zbyti
code

[+Ripdubski]

Thanks to both!  I learned multiple things with the replies.  The latter is what I was ultimately after.