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need help with IBM circa code

Started by soconne Sep 17, 2005 at 11:56 AM 4 replies 500+ views

Original Post

Sep 17, 2005 at 11:56 AM

I need a little help understanding the following code for the IBM circa machine, from the 1950's.


+0 000 000 000 (loc 0)		constant 0
+0 000 000 000 (loc 1)		index, i
+0 000 000 000 (loc 2)		sum of array
+0 000 000 000 (loc 3)		average of array
+0 000 000 000 (loc 4)		number of elements in array
+0 000 000 000 (loc 5)		temporary location
+0 000 000 000 (loc 6-999)	the array
+9 999 999 999				end of initial data
+8 000 000 004 (loc 0)		read number of elements
+8 000 000 005 (loc 1)		read data into temp
+5 005 000 004 (loc 2)		if positive, skip
-1 000 005 005 (loc 3)			else negate
-6 005 006 001 (loc 4)		move temp into array sub i
+7 001 004 001 (loc 5)		incr. i, test with n, loop to loc. 1
+0 000 000 001 (loc 6)		reinitialize i to zero
+6 006 001 005 (loc 7)		add array sub i
+1 005 002 002 (loc 8)			to sum
+7 001 004 007 (loc 9)		incr. i, test with n, loop to loc. 7
-2 002 004 003 (loc 10)		sum / number of elements -> avg.
-8 003 000 000 (loc 11)		print average
+9 000 000 000 (loc 12)		stop
+9 999 999 999				end program
+0 000 000 010 			number of input values
   input  data

The first line is simply declaring a constant of value 0, but what does the next line do? index, i ? Does anybody know what this means ? I have tried searching google for documentation but I cannot find any.

Rhalin

Sep 17, 2005 at 12:59 PM

Looks like your dealing with IBM psuedocode assembler stuff. (No, I'm not -that- good, thank you google)

http://www.mta.ca/~amiller/ibm650/650pseud.html

I hope you have a good handle on Assembly, because after giving this a brief look, I think you'll need it to understand what all this does (even though this looks nothing like most of the assembly I've seen, having the background might help).

I dont know if your going to find a definitive guide to understanding this, but I hope the link helps. I found it and a few other pages by searching google for the string (with quotes) "end of initial data" as it seemed language specific.

Promit

Sep 17, 2005 at 1:04 PM

It looks like the first 7 lines are variable declarations. The second one creates an indexing variable called i.

Rhalin

Sep 17, 2005 at 1:09 PM

I've just been reading some of the docs I've found on this style of pseudocode (it piqued my interest)..

It appears that the phrases/sentances in the right most column (sum of array, constant 0, average of array) are comments. So everything before "+9 999 999 999 end of initial data" is variable initializations at specific locations.

Using that page I posted earlier and this one:

http://www.augustana.ca/~mohrj/courses/common/csc370/lecture_notes/interpreters.html

You might be able to translate all those machine codes into something you can understand, at the moment, I'm a little ill, otherwise I might do it just out of curiosity ;)

Speaking of which, what are you doing this for anyways, just wondering?

soconne

Sep 17, 2005 at 1:25 PM

Hey thanks a lot guys. I'll take a look at those links.

I'm in a software projects class and my team is working with the IBM circa and we're trying to understand the machine code.

JohnBolton

Sep 17, 2005 at 4:20 PM

BTW, there is no IBM computer named "circa".

"circa" in this context means that a date is approximate or that it indicates a period in time around that date. "circa 1950" means "sometime around 1950" or "typical of the year 1950".

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