How can you compare C and Assembly? All you can do is compare a certain C
compiler (and\or programmer) with a certain Assembly compiler (and\or
programmer). It all depends on situation. The compiler(\programmer) and
project would have more influence than the language in most cases. If you're
doing DSP and you use a good C compiler with highly optimised assembly DSP
routines then it could easily be faster than your code cause someone spent a
lot of time writing good asm routines and they knew the architecture and the
problem better than you.

In general you CAN optimise assembly more than C in all cases but are you
better at optimising assembly than the people who wrote the C compiler?

Tom.

-----Original Message-----
From: Quitt, Walter [mailto:wquitt@MICROJOIN.COM]
Sent: Thursday, April 13, 2000 10:05 AM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: Question: C vs Asm


Wait till you fill (max) your part up (out)!
Trying to minimize implemented and working code is not simple.
One project is at 14K lines of ASM code (14 KLOCs) in a 16K part.
I even moved some constant overlay tables and LCD screens to serial EEPROM.

YES, for programming in the SMALL or simple stuff, C is GREAT.
But real-time, speed critical stuff is real hard to do well in C.
Sorry, that's MHO after years of doing real-time code and now
for the last 2+ years almost full time on PICs.

BTW: Using the BANKSEL and PAGESEL directives allows you to
write (basically) totally relocatable (modular/reusable) code
pieces in MPASM.  So you can have C drivers calling the ASM
fast/tight ASM routines.  There's something to be gained there,
I think.  Therefore, almost no worries about those pesky banks.

Also, from a maintenance standpoint poorly written or documented C
can be just as hard (or easy) to work with as similar ASM.
Been there and certainly done that!

BTW: I do both C and ASM.
"It is left as an exercise for the reader to determine which I like more!"

Hint: I don't even know, I just like to see the moving machines and
blinking lights......

Walt...
-----Original Message-----
From: Erik Reikes [mailto:ereikes@XSILOGY.COM]
Sent: Wednesday, April 12, 2000 4:47 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: Question: C vs Asm


In the PIC projects I write I use C almost exclusively.  The reason for
this for me is ease of code reuse, ease of readability, and its just plain
old easier to write in.  I never have to worry about code page bits, ram
bank bits, local variables, etc. etc.  Also, I have ported a number of
complicated functions written for other platforms quite easily to the PIC.

The detriments are slightly larger code size which I mitigate by being
careful about how and what C statements I use and when.

Now for the PIC, a C compiler really just ends up being a really excellent
Macro Assembler, but the benefits are huge.  I wouldn't recommend to anyone
starting out to start writing programs exclusively in ASM.  Its very
important to know the PIC ASM commands, but that is primarily just for
verification when something doesn't work right, and when occasionally you
must write something very time intensive.

My estimates for the medium sized project that I am working on currently
that C is costing me about 25% of my code space.  A lot of this is due to
sheer laziness because we have a ton of extra space currently.  The gain in
time spent implementing and debugging, however, is well over 90%.  As in I
believe it would take 10x as long to develop and debug this program in
straight assembler.

YMMV





Erik Reikes
Senior Software Engineer
Xsilogy, Inc.

ereikes@xsilogy.com
ph : (858) 535-5113
fax : (858) 535-5163
cell : (858) 663-1206