IBM 610 Auto-Point computer (annotated)
Have you ever gone into your pantry, closed your eyes, randomly picked out the first dozen ingredients, and challenged yourself to make a dinner from whatever you grabbed? Well, it sure seems like that's how IBM designed the 610 computer.
Programming the machine
Lights, more light, other more lights.
The keyboard includes a set of lights that help you figure out what the computer is doing, and a set of "check" lights.
The actual little numbers 0..9 aren't displayed; you just have to kind of squint and carefully measure where the little dots are. It's not (seemingly) calibrated, and each column can only display one dot. No, you can't display DOOM on this.
The main body of the computer also has lights, this time to tell you what the current program step and current registers are, plus whether the machine is off, on, or really on.
You might also want to program with fancy "if" statements. Those are available when you use the paper tape. The paper tape uses an 8-channel (8-bit) code. The top two bits say what "class" any particular instruction is in -- classes 0, 1, 2 and 3. You can specify which classes of instructions you want to run at any time. Yes, this means you a main body, a "if-else" statement, and a remaining "if" statement, and that's it. But good news: you can interleave the different statements together.
But wait -- which class gets used? Answer, of course, as with everything about this machine, is that it depends, There's four switches on the manual keyboard, one for each class, and they can be set to "always", "never" and "depends on the programming panel".
That auto-point isn't really floating point
IBM was really happy with their "auto-point" concept. If you've never used the previous technology -- which would be a "slide rule" -- those devices don't include the magnitude of the number at all. That is, you multiply "1.23" x "6.78" in the exact same way that you multiply "123" x "678" -- you just have to remember where the decimal point is.
With the "auto-point" concept, you get a bunch of registers, each of which can hold some numbers like "1.23" or "6,780". As you enter each number in, when you get to the decimal place, the number will automatically adjust in the machine so that the integer "left side" of the decimal point uses half of your register, and the fractional remainder goes into the right side of the register.
On the one hand, this is convenient: you don't have to remember where the decimal point goes in your result of 83394. On the other hand, very large and very small numbers are absolutely impossible, and your precision will vary all over the place.