🚀 go-pugleaf

In article <444@nikhefh.hep.nl> t68@nikhefh.hep.nl (Jos Vermaseren) writes:
>The reason that some programs like Tempus have such a fast screen has several
>reasons:
>1:	The screen routines are user routines that are directly accessible
>	for the program. They are written in such a way that it is not
>	necessary to save registers.

	The saving of registers actually represents a very tiny fraction of
the time used by a typical "fastprt()" (as mine is called) routine.  This is
because fastprt() is called with a whole string, rather than a character at a
time.  The bulk of the time consumed is the simple loop that loads a
character, finds the offset into the bitmap array, then copies 8 or 16 bytes
of bitmap data to the screen. 

>3:	Absolutely no interpretation of tabs takes place. A good tab handler
>	would slow the output down by about a factor two (guestimate).

	Actually, handling tabs adds perhaps 0.1% of overhead, with respect to
time taken.  The same goes for handling the ESC codes, too, since all that is
added is one compare instruction, as in:

	<load character into register>
	cmpi.b	$ESC,<register>
	bgt	not_ESC

	...	/* Processing of ESC, TAB, CR, LF, ... */

not_ESC:
	...	/* Regular character handling */

As you can see, if a given character is _not_ a control character (i.e.  it is
greater than 27), then all that is executed is the "cmpi.b" instruction.  This
adds essentially no time, when compared to the total time taken to print a
typical string. 

--
	- Jonathan A. Fischer,    jafischer@lily.waterloo.edu
...{ihnp4,allegra,decvax,utzoo,utcsri}!watmath!lily!jafischer
	Pascal SUCC()'s.