Re: 1980 Basic Sought

On Tue, 08 Apr 2008 00:21:08 -0500, ArarghMail804NOSPAM wrote:

> On Mon, 7 Apr 2008 23:08:17 -0400, "Tom Lake" <tlake@[EMAIL PROTECTED]
>
> wrote:
> 
> <snip>
>>
>>CHR$(PEEK(SADD(a$))) turns that ASCII value back into a character and so
>>the letter T will print.
> 
> Ok, I see where you are going.
> 
> Won't work with PDS or VBDOS far strings, as those strings are not in
> the "DEF SEG".
> 
>  .
> 
>  .
> 
> Wouldn't "LEFT$(a$,1)" be a lot easier?  :-)

I couldn't afford PDS, but I'm sure it used string descriptors and had 
functions that worked like and VARPTR, VARSEG and SADD.  Some of the 
things we used to use string variables for weren't really strings.  On 
the TRS-80 and CP/M systems, we used to build custom functions by packing 
machine code into a string and using VARPTR to find its address.  Before 
the coming of Windows, when video RAM ocntained ASCII data, you could 
POKE values into a string's descriptor to make that variable point to a 
field on the screen.  You can twiddle with descriptors to quickly swap 
the values of two large string variables.  Since a string descriptor 
contains a pointer, you can use it to get around QuickBasic's lack of 
pointer variables to do many of the tricks that C allows (including 
shooting yourself in the foot).