Instruction Set (1951)
| Arithmetic and logical orders | |
| A n | As before |
| S n | As before |
| Phi (#) n | Transfer to location n the most significant part of the accumulator, clear the accumulator and then, if the capacity of the accumulator has been exceeded since the accumulator was last cleared, stop the machine, light the 'accumulator overflow' lamp and give audible warning |
| U n | Copy the more significant part of the accumulator into location n, but retain the whole content of the accumulator |
| T n | As before |
| H n | As before |
| V n | As before |
| N n | As before |
| Y n F | Round off the number in the accumulator to 34 binary digits; that
is, add 2^-35 to the accumulator.
This is not the same as Y n D |
| C n | As before |
| M n | Clear the 6 most significant digits of the accumulator and then add the content of location n into the accumulator |
| N n | As before |
| Shift orders | |
| R D | Shift the accumulator one place to the right |
| R 2^(n-2) F | Shift the accumulator n places to the right |
| R F | Shift the accumulator 15 places to the right |
| L D | Shift one place to the left |
| L 2^(n-2) F | Shift left n places |
| L F | Shift left 13 places |
| Jump orders | |
| F n F | Jump to order n |
| F n D | If accumulator is not zero, jump to order n, otherwise proceed serially |
| E n F | If accumulator is positive or zero, jump to order n, otherwise proceed serially |
| E n D | If accumulator is positive or zero, clear the accumulator, and jump to order n; otherwise proceed serially |
| G n F | If accumulator is negative, jump to order n; otherwise proceed serially |
| G n D | If accumulator is negative, clear the accumulator and jump to order n; otherwise proceed serially |
| Y n D | If the capacity of the accumulator has been exceeded since the last Y n D order was encountered, clear the accumulator and jump to order n; otherwise proceed serially |
| B-register orders
I have no idea what this is about - I'll have to look! |
|
| B n | Replace the content of the B register by the NUMBER n (not the contents of location n) |
| J n F | If the B register is not zero, jump to order n; otherwise proceed serially |
| K n F | Place the order B b F (where b is the content of the B register)
in storage location n
NB: this does not clear the B register |
| Input and output | |
| I n F | As before |
| O n F | As before |
| Orders which stop the machine | |
| Z n F | As before |
| Z n D | (a) If the ZD switch is on, this order operates like ZnF above
(b) If the ZD switch is off, this order has no effect, and the machine passes straight on to obey the next order |