Programming the IBM 1620

Posts: 410 · Posted: Thu Dec 30, 2004 1:02 pm

Ladies and gentlemen… I, A.O. Kime, being of sound mind and body, am proud to introduce and open this vital question and answer series on “Programming the IBM 1620”! While it may be a little dated (40 years), nonetheless citing from my 1965 instruction manual (by Eric A. Weiss), I will surely inform and amaze everyone! (I had to find some means Rolling Eyes

)

Note: This thread was thought necessary and insisted upon by Jamie Price (forum administrator)… “I don’t want our forum to be lacking anything” Jamie said, “after all, someone, somewhere, may still operate an IBM 1620”. Jamie continued to say… “Besides, I might have been wrong for believing Fortran was “klunky””.

Trivia: The IBM 1620, having only a memory of 20,000 ‘cells’, nonetheless this limited memory capacity (for those days) was enough to get man to the moon (1969).

Question: Is “FIRST” (Fortran) a floating point variable or a fixed point variable? (this is not a multiple choice question… with simply an (x) box to check (being too easy), you must spell out which it is)

Posts: 1029 · Posted: Thu Dec 30, 2004 1:45 pm

Is that some sort of trick question? FIRST is referring to a Variable name isn't it? However, since variables in FORTRAN reference Memory Addresses and not information held as a "variable", and taking a wild guess since these variable names should be good descriptors of the type of information being held in that block of memory, I'm going to say that FIRST is referring to a FIXED POINT VARIABLE.

Posts: 746 · Posted: Thu Dec 30, 2004 2:26 pm

I think I remember reading somewhere that the 1620 was a pure decimal machine. Therefore I'm going to say that the varible FIRST on a 1620 in FORTRAN is a Fixed Point Variable

That is unless of course you wanted to drop a few more tens of thousands of dollars and get the FP hardware...while you were at it, toss in a few more thousands and you could pick up the necessary hardware to give you the ability to divide numbers while you were at it...

Posts: 1029 · Posted: Thu Dec 30, 2004 2:30 pm

LOL!!! Well if that's the case, then I'm right... but not nearly as right as I'd like to be lol... right answer, wrong reasoning.

Posts: 17 · Posted: Thu Dec 30, 2004 3:06 pm

My first language was Fortran on punch cards, but was on a IBM360. Had to use JCL to setup PDS (Partitioned Data Sets) on the Disk pack or tape in some cases. If i remember right we had to be careful to programs the dataset on the disk sectors so that it would be easy to access. And it required that the data was defined in JCL prior to execution.
Lets keep this one going.
thanks
kes

Posts: 1029 · Posted: Thu Dec 30, 2004 3:07 pm

Welcome to the Dev Forums, Kurt!!! And yes, please do keep this one going... im gonna learn some stuff next week LOL!!!

Posts: 17 · Posted: Thu Dec 30, 2004 5:19 pm

Question: did the 1620 use CORE for memory? I believe so.
I have an oppinion on Fortran being klunky: I still to this day love Fortran and think it was a nice compact structured language. It was a precursor to Pascal, C, PL/1 (well lets not talk about PL/1 Embarassed

), ... in terms of structure. And ya-know it worked. But i have to confess i likewise liked RPG on the system 3, all the way up to RPG/400. So i guess you have to take my oppinion from where it comes Laughing

thanks
kes

Posts: 766 · Posted: Thu Dec 30, 2004 5:21 pm

Note: This thread was thought necessary and insisted upon by Jamie Price (forum administrator)… “I don’t want our forum to be lacking anything” Jamie said, “after all, someone, somewhere, may still operate an IBM 1620”. Jamie continued to say… “Besides, I might have been wrong for believing Fortran was “klunky””.

To paraphrase Oliver North, "I have no recollection of the events of that particular conversation."

Posts: 17 · Posted: Thu Dec 30, 2004 5:25 pm

Private message stuff may not have a place here, but for this one time it just seemed approprate!

Posts: 1029 · Posted: Thu Dec 30, 2004 5:35 pm

PM's? Are you kidding? I use them all the time to harass the staff. Wink

I didn't get a PM Sad

Im hurt... lol j/k

Posts: 410 · Posted: Thu Dec 30, 2004 9:57 pm

Children, children... what is a teacher to do? Bobum, you and Josh have to pay attention more! Rolling Eyes

The question concerns the function of "FIRST".

A Fortran fixed point variable name contains five or fewer alphameric characters starting with I, J, K, L, M, or N. The value of a fixed point variable is a four-digit integer.

A Fortran floating point variable name contains five or fewer alphameric characters starting with any letter not I, J, K, L, M, or N. Its value is a decimal number in exponential form with an eight-digit mantissa.

Therefore "FIRST" is a floating point variable.

And no, Josh, a mantissa is not a rock indians use to grind corn.

Posts: 410 · Posted: Thu Dec 30, 2004 10:14 pm

Okay students, discuss that one for awhile... I'll be back later with another question.

I should add this paragraph (one I got a kick out of)

12-10 Get Off the Machine

After the compilation of Variation 3 has been completed, take the source program out of the Card Reader stacker, replace the card with the INPUT label in the deck, and put a rubber band around the little deck.

Remove the punched cards from the Card Punch stacker and put a rubber band around this deck. (The last two cards will be blank.) Remove the printed material from the typewriter, release the machine to the next user, and return to your desk to consider what you have done

.

For me, considering what I had done was my problem!!

Posts: 410 · Posted: Thu Dec 30, 2004 10:54 pm

Oops, sorry Kurt---- your question was

“did the 1620 use CORE for memory? I believe so."

This is how it is defined:

1-3 Storage

The storage area or memory of the computer consists of 20,000 cells, each one of which contains a single decimal digit (0,1,2,3,4,5,6,7,8,9). The storage area may be thought of as a large sheet of paper divided into 20,000 blocks in each of which a single digit may be written in pencil, together with an eraser so that the written digits may be changed. Some of the computer instructions can change the contents of these cells or blocks (for example, by adding to the contents or replacing them) while other instructions will simply refer to the contents of some cells and make use of these contents without changing them. (The former instructions may be thought of as being able to write in a cell, while the latter instructions may be thought of as reading the content of a cell without destroying it.) Every single cell in storage has a name which is called its address. The address of the first cell is 00000 and the address of the last cell is 19999. Intermediate cells have intermediate numbers for addresses. One must carefully distinguish between the address of a cell (which must be a five digit number) and the contents of the cell (which must be a one digit number). The address is like the street address of a house and is fixed. A given cell always has the same address. The content of a cell is like the present resident of the house; it may be changed. Depending on what instructions the computer has carried out in the past, any digit may be in any cell at any time.

There was no reference to "Core" at all, perhap it became a later term.

Posts: 10 · Posted: Fri Dec 31, 2004 1:28 am

Where are those Sperry Univac manuals my dad had laying around when I need'em...

Posts: 410 · Posted: Fri Dec 31, 2004 3:33 am

Yeah, cepler, that may be my only salvation here... nobody has a way to check what I'm saying. Don't look too hard, okay? Smile