HP 9100 programming questions

Howdy, I am fooling with a 9100B calculator that used to be on exhibit, I'm guessing in the electronics museum that used to be at Foothill College. Toward that end it was hacked: a plexiglas strip was screwed to it above the switches, with cutouts for the switch handles that only let you move the power switch -- program/run, fixed/floating, and degrees/radians were all stuck on run, fixed, radians respectively. Well, I've removed that because I want to find out what if any programs were in its memory (core remembers things long after they're better forgotten), and so I want to flip the program/run switch over to PROGRAM. But I'm a little confused about the 9100's program mode, and unfortunately I don't have the manuals handy. When I flip the switch to PROGRAM, the display changes to what I am guessing is this: <step> <instruction> <Y mantissa> <Y exponent> <X mantissa> <X exponent> <step> seems to be represented as <hex digit>.<hex digit>. True? (And does this mean there are only 256 program steps?) Are <instruction> values 00-09 the keypad switches 0-9, and others in <column><row> form? And if so, where's <0><0> for the <column><row> form? Can I use the STEP PRGM key to single-step forward non-destructively in program mode? How can I move backward, or to a given location in program mode? Can y'all tell I'm spoiled rotten from having learned programmable calculators about 15 years later? -Frank McConnell