🚀 go-pugleaf

Douglas Evan Cook (cookd@bert.cs.byu.edu) wrote:
: On 25 Nov 1995, Arcadio Alivio Sincero wrote:

: > 
: > I was reading a FAQ on the Modula 3 language, and it said amongst the 
: > things it adds to Modula 2 is the support of lightweight processes, or 
: > threads.  Now, I thought this functionality was already present in 
: > Modula 2.
: > 
.......
: > 
: > Arcadio
: > 
.......
: For example, 
: a clock process would display the time, then pass control back.  It would 
: regain control, depending on what kind of process it is, either on the 
: clock tick or when the main process decides to update the clock (when 
  ^^^^^^^^^^
: waiting for keystrokes, etc.).  
: Douglas

The difference between direct and indirect process control is obvious :
you should program it by yourself ( it is not a case of 'threads' ), or 
gaining control by processes
is controlled by 'manager' - this is the case of threads.
Most famous DOS and OS/2 implementation of Modula2 - TopSpeed M2
contains both variants of multitasking. I have used process manager for
emulating concurrent processes in DOS environments, and it works great
on 8088 IBM PC XT.
But a thread process manager was not included in 'standard M2' by N.Wirth.
You know, M2 was designed and implemented as a system programming tool,
and and writing such a threads using M2 is straightforward. 
BTW, TopSpeed implementation of M2 contains source code ( in M2 ) of their
process manager. I also think, that any implementation of M2 contains at
least the needed primitives ( part of standard M2 ) for writing threads, or
thread process manager for given machine/OS.
Hope this helps, Valentine.