Don wrote:
Walter Bright wrote:
Don wrote:
[1] What was size_t on the 286 ?
16 bits
Note that in the small memory model (all pointers 16 bits) it really
was possible to have an object of size 0xFFFF_FFFF, because the code
was in a different address space.
Not really. I think the 286 had a hard limit of 16 Mb.
I mean, you can have a 16 bit code pointer, and a 16 bit data pointer.
So, you can concievably have a 64K data item, using the full size of
size_t.
That isn't possible on a modern, linear address space, because the code
has to go somewhere...
Actually, you can have a segmented model on a 32 bit machine rather than a flat
model, with separate segments for code, data, and stack. The Digital Mars DOS
Extender actually does this. The advantage of it is you cannot execute data on
the stack.
There was a so-called "huge" memory model which attempted (badly) to
fake a linear address space across the segmented model. It never
worked very well (such as having wacky problems when an object
straddled a segment boundary), and applications built with it sucked
in the performance dept. I never supported it for that reason.
A lot of the effort in 16 bit programming went to breaking up data
structures so no individual part of it spanned more than 64K.
Yuck.
I just caught the very last of that era. I wrote a couple of 16-bit
DLLs. From memory, you couldn't assume the stack was in the data
segment, and you got horrific memory corruption if you did.
I've got no nostalgia for those days...
I rather enjoyed it, and the pay was good <g>.
