If the number in switch 741 is to be subtracted from the number in storage counter 321, the instruction is changed into:
- Take the negative of the number in switch 741;
- transfer it into storage register 321;
- read the next line of coding
The coding line becomes:
741, 321, 732
By putting 32 in the C field, we cause the number in switch 741 to be subtracted from whatever number is in register 321.
We have 2 more choices in adding and subtracting. The value of the number without regard to sign—in other words, its absolute value ([see Supplement 2])—may be added or subtracted. The instruction
Add the absolute value of
is expressed by a C field code 2, and the instruction
Add the negative of the absolute value of
is expressed by a C field code 1.