RE: New to RPG

It was the 1890 census. It took years off the time to tally the census. Sadly, most of the census documents and the Hollerith cards were lost in a fire in the early 1920s.

Dave Shaw
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Sent from my Windows 10 phone

From: Jon Paris
Sent: Thursday, April 27, 2017 6:16 PM
To: Rpg400 Rpg400-L
Subject: Re: New to RPG

Many many moons ago when IT was in its infancy there was a category of early "computing" devices known as tabulators. They first appeared to the public as the means by which the US census was tallied at some point - I don't recall the year and it is not relevant right now.

Tabulators processed punch cards (See https://en.wikipedia.org/wiki/Punched_card if you don't know what they are).

Data is represented in the card by a series of holes punched in the card. The most common format before they became obsolete was the 80 column card. Each card could hold 80 characters of information.

The data from the cards was read by the cards being fed over metal rollers with a brush making contact from above - one brush for each column. When there was a hole in the card the brush made contact with the roller and a current flowed though the brush. The timing of that current was used to determine if the value being sensed was a 1, 2, 3 or whatever.

But if totals etc. needed to be produced, then you needed to know when the following card had different values in specific columns (say the account number) from the one that preceded it. This was achieved by having not one but two read stations (three in some machines but that is another story). By comparing the electrical currents coming from read station 1 with those from read station 2 you could tell when this "Level Break" took place.

Welcome to the RPG cycle and level breaks! They were designed to provide a simulation of the original punch card equipment.

P.S. Indicators (*IN03 etc.) are from the same heritage. By connecting a wire from a specific column to an output that always provided a current at a specific timing point you could "turn on" an indicator when (say) column 1 contained a "5" or a different indicator if it contained a "6".


Jon Paris

www.partner400.com
www.SystemiDeveloper.com

On Apr 27, 2017, at 3:38 PM, Douglas Dunn <dunndouglas0@xxxxxxxxx> wrote:

As another young developer just getting into iSeries, I promise to only
write new software with the modern techniques. And I should probably get
RDi. I am still curious about the old fixed-form style, mainly because the
syntax looks very exotic to me. Can someone explain the concept of the
"cycle" that was mentioned about?

On Thu, Apr 27, 2017 at 12:23 PM, Charles Wilt <charles.wilt@xxxxxxxxx>
wrote:

On Thu, Apr 27, 2017 at 12:38 PM, James H. H. Lampert <
jamesl@xxxxxxxxxxxxxxxxx> wrote:

SCREW UP A LOT OF RECORDS VERY FAST, WITH NO WAY TO HALT THE CARNAGE AT
ONE DAMAGED RECORD.

​ROLLBACK;

​
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