[Info-vax] Android development Was Re: OT: Larry Ellison takes retirement as CEO of Oracle

[JF Mezei]

On 14-09-21 11:03, Johnny Billquist wrote:

> Essentially correct, although there are no IO instructions per se, but 
> various system calls, both for loading in dynamic libraries, grabbing 
> memory, and doing I/O.

Gow does an IO actually get done ?

So you "branch" to the driver, driver sets up registers and deposits
values at the correct physical memory locations and then what ? Does the
device get the "order" to perform an IO when a certain value is
deposited at a certain location ?  or is there an assembler instruction
to trigger an IO for the device specified in the argument next to the
assembler opcode ?


IBM 360 assembler has the "WTO" instruction (or macro) which is "write
to operator" (but at Uni, it really meant "write to output" since the OS
(Music) didn't allow students to send messages to the operator console
:-)  And interssting that it is able to perform differently on different
operating systems. (on MVS, it really does pop a message up to the
operator console, but on Music, it goes to the user terminal, even if
both instances run on smame physical machine over VM)