IBM 1401 Runs FORTRAN II Once More

February 11, 2018 by Adam Fabio 41 Comments

The IBM 1401 is undeniably a classic computer. One of IBM’s most “affordable” mainframes, it ruled the small business computing world of the 1960’s. Unfortunately, computers aren’t often thought of as treasured heirlooms, only a handful of these machines survive today. The computer history museum has two machines. One from Germany, and the other recovered from a basement in Connecticut back in 2008. [CuriousMarc] and the rest of the team at the museum have been working diligently to restore the 1401, and they’ve hit quite a milestone — They can now compile and run FORTRAN II code.

Getting the 1401 to run FORTRAN II itself is quite an accomplishment. The hardest part was dealing with the 729 vacuum column tape drives. The team spent years building a hardware emulator which takes the place of the real drives. The emulator is driven by an old PC running windows. Tape images are stored as files, which can be loaded, rewound, and run just like a real 729.

Emulators are great, but [Mark] and his team wanted this to run on the real hardware. They first had to re-create a FORTRAN compiler tape. They ran a tape copier program on the 1401, then loaded an image of the compiler on their emulator. The computer dutifully copied the image to a real tape drive.

The team also needed a punched card deck of FORTRAN source code to compile and run. The first example in the FORTRAN manual is a Hilbert Matrix program. The team could have used a keypunch machine to punch the cards for the program, but that is a painstaking and error-prone process. One mistake, and they would have to re-punch an entire card — much like using an old typewriter with no White-Out or correction ribbon. Instead, they typed the source into a PC, then converted the file to a tape image. A small program instructed the 1401 to punch the source code out on cards for them.

At the moment of truth, shown first in the video, the 1401 reads FORTRAN II from tape, pulls in the source code from punched cards, compiles, runs, and then prints the result on its line printer. All the original hardware singing along just like it did in 1959.

If you haven’t been to the Computer History Museum yet, check it out! It’s also the site of Vintage Computing Festival West.

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Commodore 1530 Datasette Gets A Digital Counter

August 9, 2014 by Adam Fabio 25 Comments

Ah, the humble Commodore 1530 Datasette drive. It never enjoyed much popularity in the USA, but it was the standard for quite some time in Europe. [DerSchatten13] still uses and loves his 1530. When a co-worker showed him some 7-segment bubble LEDs, he knew what he had to do. Thus the 1530 digital counter (translated) was born.

[DerSchatten13] started out by building his design on a breadboard. He used every I/O pin on an ATtiny2313 to implement his circuit. Tape motion is detected by a home-made rotary encoder connected to the original mechanical counter’s belt drive. To keep the pin count down, [DerSchatten13] multiplexed the LEDs on the display.

Now came the hard part, tearing into the 1530 and removing the mechanical counter. [DerSchatten13] glued in some standoffs to hold the new PCB. After rebuilding the circuit on a piece of perfboard, he installed the new parts. The final result looks great on the inside. From the outside, one would be hard pressed to tell the digital counter wasn’t original equipment.

Operation of the digital counter is identical to the analog unit – with one exception. The clear button now serves double duty. Pressing and holding it saves the current count. Save mode is indicated by turning on the decimal point. If the user rewinds the tape, the counter will stop the motor when the saved count is reached. Cueing up that saved program just got a heck of a lot easier!

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A Nostalgic Look At What A 13 Year Old Can Do With A C64

November 13, 2012 by Mike Szczys 41 Comments

[Armin] recently pulled out his Commodore 64 and looked back on the projects he did as a kid. The surprising thing is that we’re not talking quite as far in the past as you might image. He was 13 in 2002 and the family didn’t have a PC. But more than a decade before his father had purchased a C64 and [Armin] dug into the manual to teach himself how to code. This week he connected the old hardware to his video capture card to give us a demonstration on what he accomplished.

He had seen Windows 95 at the local computer club and figured why not program a clone of the software for the machine at hand? He called it Windows 105 (because that number is higher than 95) and worked out ways to mimic programs like DOS, Corel Draw, Notepad, and some of the programs from Microsoft Office. They didn’t include all the functionality of the real thing, but the look was there.

The story does have a happy ending. [Armin’s] parents saw what he was doing and managed to pick up a PC for him to play with. Now he’s a professional programmer looking back on the formative years that got him there. We’ve embedded one of his demo videos after the break for your enjoyment.

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