Bullshit System/360 fix exposed to all • The Register

Who I? A to register The reader is tripped up by the curse of software updates decades before Patch Tuesday was a wink in Microsoft’s eyes. Some things never change. Welcome to Who Me?

Our story this week comes from “Ivor” thanks to his experience with punch cards and the IBM System/360 Model 40.

This particular kit was aimed at companies that had outgrown simpler hardware. There were rows of lights, magnetic tape, and dryer-sized magnetic disk units. CRTs were yet to appear at Ivor’s facility, but punch cards were still used for programming purposes.

And exit? About a typewriter chugging along at about 12-15 characters per second.

After the computer spat out the required message, it used the typewriter to punch out “READY FOR COMMUNICATIONS” – informative, yes. Efficient? Not really. Not considering how many times a day the operators were confronted with the message.

“Fortunately,” Ivor said, “IBM back then provided the operating system in the form of a box of punch cards (source code) that were assembled into executable files, so for those who were interested, you could replace a few or many punch cards and change the operating system.”

“There were magazines that published code modifications for various improvements, and as a junior assistant sysadmin, a code update that would reduce the operator message to something shorter seemed like a big improvement.”

The next time the system was updated, Ivor made a change. The message text has been updated and in another module the length in the print command has been set to two.

“The operations staff loved me,” he recalled happily, “because now instead of the long previous status message, they were presented with ‘GO’.”

months passed. Ivor turned to other projects. He was therefore caught off guard when the inevitable call came.

Turns out something strange had happened to his message. Software updates were released every six months and someone had helpfully injected them into the computer. An update affected the module responsible for printing the status message, effectively reverting Ivor’s two-character acceleration.

Operators were somewhat alarmed by the performance.

“What the hell is that?” asked the data center manager, pointing to the console’s typewriter.

Ivor peered to the side. Instead of a cheerful “GO”, the entire message was printed. And Ivor had really been a very naughty boy.

The “GO” was still there, but it was followed by a strongly worded suggestion (in deference to more sensitive eyes) that the operator might like to, er, walk away.

The message had been repeated over and over again.

“It seems that the last update had replaced the print command with one with the original message length, but my replacement message, which never saw the light of day due to a truncated print command message length, was now visible to all.”

Ah, the joy of receiving a call when a long-forgotten code explodes in a user’s face. Would you have resolved the problem quickly, or adopted a weird voice and pretended the caller dialed the wrong number? Confess everything with an email to Who, Me? ®

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