Re: A86: ld HL call
[Prev][Next][Index][Thread]
Re: A86: ld HL call
>From: BlAsTo1414@aol.com
>Date: Mon, 14 Sep 1998 00:11:47 EDT
>To: assembly-86@lists.ticalc.org
>Subject: A86: ld HL call
>Reply-To: assembly-86@lists.ticalc.org
>
>
>ok,
>
>I saw in an example prog the folowing code:
>
>
> call _clrLCD ; clear the screen
> ld hl, $0000 ; stores $00 in h, $00 in l
> ld (_curRow),hl ; stores 0 in _curRow, 0 in _curCol
> ld hl, Hello ; hl points to string Hello
> call _puts ; print the string
> ld a, '!' ; load ! character in A
> call _putc ; print '!'
> call _newline ; go to next line
> ret ; return from program
>
>
>The seconline of that reads:
> ld hl, $0000
>is that making sure that 'hl' has nothing in it so that the next
command:
> ld hl, Hello
>can make hl be whatever 'hello' is?
>
>also, what does this mean:?
> call _putc
>is that putCHARACTER?
>and putS is putSTRING?
>
>but how does 'putc' know to read the character in 'A'?
>
>just a few questions,
>BlAsTo1414
>
No the $0000 sets the cursor position to 0,0 (upper left corner).
Notice how after $0000 is put into hl its then loaded to (_curRow) so
that the cursor is moved to that spot. And even if hl has something in
it I beleive if you load something into hl it'll just overwrite what was
already there with the new data. If you look at the comments and read
them out as a sentence it usually tells you very clearly what is
happening (notice I said usually not always). And you were right about
the _puts and _putc things. Also -putc knows to use the a register
because that is what is programmed to do.
______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com