27 Jul
2010
27 Jul
'10
3:25 p.m.
Chuck Guzis wrote:
On 27 Jul 2010 at 21:42, Tony Duell wrote:
Or some machines like the
one I am working on; one does not even have
a CALL of any kind. It is not needed.
TAD I [.+1
JMP SUB
It doesn;t have to be a CALL in the normal sense
(i.e. it stacks the
PC contents, it might just save the PC in some other register (or in
the word preceeding the subroutine itself, or..)
I meant it in that sense--i.e., the value of the
current PC is saved
(on a stack, in memory or in a register) and is program-accessible
(not all CPUs allow this) and a transfer of control occurs. It's
only people born since 1970 who think that all machines have hardware
stacks. Consider it to be equivalent to a TSX, RJ or BAL instruction
if you desire. (The first time I heard someone referring to S/360
BAL, I thought "Boy, that's pretty silly, limiting yourself to one
instruction.").