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Multi module CP/M assembly programming question.

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    Multi module CP/M assembly programming question.

    I have a couple simple routines.

    HELLO.MAC
    Code:
    .z80
    extrn print
    
    start: ld hl, msg
        call print
        ld c, 0
        call 5
        halt
    
    msg: db 'Hello',0
    end start
    And PRINT.MAC
    Code:
    .z80
    
    public print
    
    print: ld a, (hl)
        cp 0
        ret z
        inc hl
        push hl
        ld e, a
        ld c, 2
        call 5
        pop hl
        jr print
    
    end
    The editor butchers this a bit.

    I assemble and link them using M80:
    Code:
    m80 =hello/l
    m80 =print/l
    l80 hello/n,print/n,hello/e
    
    Link-80 3.44 09-Dec-81 Copyright (c) 1981 Microsoft
    
    Data 0103 0215 < 274>
    
    -PRINT 0207
    
    1 Undefined Global(s)
    
    48927 Bytes Free
    
    [0203 0215 2]
    I don't understand why it can't find PRINT.

    Also, how does it know to start at 100 with no ORG statement?

    #2
    Why the "/n" after the object files in the L80 invocation? You're essentially telling L80 to produce hello.com and print.com, not link them.

    Try this:
    Code:
    Link-80 Release 3.36 29-Feb-80
    *hello,print
    Data 0103 0124
    
    
    
    *hello/n/e
    
    Data 0103 0124
    
    [0103 0124 1]


    Last edited by Chuck(G); December 20, 2021, 02:49 PM.
    Reach me: vcfblackhole _at_ protonmail dot com.

    Comment


      #3
      Originally posted by Chuck(G) View Post
      Why the "/n" after the object files in the L80 invocation?
      Because I don't know what I'm doing.

      Try this:
      Code:
      Link-80 Release 3.36 29-Feb-80
      *hello,print
      Data 0103 0124
      
      
      
      *hello/n/e
      
      Data 0103 0124
      
      [0103 0124 1]
      Yes, this worked a peach. Thank you.

      How do you find how much "free" memory you have after you load the program?

      Specifically, how do you know where memory starts after your code and how far you can go?

      I've seen folks grab the address from BDOS call to find "top of memory". But what about the end of my code?

      In a simple assembly program, you just have a label at the "end" and that's the start of memory.

      But how does that work when you have several modules? How do you order that?

      Also, is there a way to get a symbol table out of L80?

      Thanks for the help.


      Comment


        #4
        Look at location 5--that's a jump to BDOS. Zero out the low byte of that jump address and you have the beginning of BDOS. That gives you the limit to high memory. You can overwrite CCP with no problems as BDOS will reload it at program termination.

        As far as the end of your code, that's up to you to determine. You can define a symbol at the end of the last module loaded, for example.

        You can get a rudimentary symbol table from l80 with the /m switch. But really, l80 is pretty primitive--DRI Link80 is far more powerful.
        Last edited by Chuck(G); December 22, 2021, 09:16 AM.
        Reach me: vcfblackhole _at_ protonmail dot com.

        Comment

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