MIT PDP-10 'Info' file converted to Hypertext 'html' format by Henry Baker

Boolean Logic

There are 16 possible boolean functions of 2 variables. The PDP-10 has 16 instruction classes (each with 4 modifiers) that perform these operations. Each boolean function operates on the 36 bits of AC and memory as individual bits.

[The original had a typo; ORCA was in there twice instead of ORCM. The table below has been rearranged in opcode order. -Joe]

     C(AC)   0       1       0       1
     C(E)    0       0       1       1

400  SETZ    0       0       0       0       SET to Zero
404  AND     0       0       0       1       AND
410  ANDCA   0       0       1       0       AND with Complement of AC
414  SETM    0       0       1       1       SET to Memory
420  ANDCM   0       1       0       0       AND with Complement of Memory
424  SETA    0       1       0       1       SET to AC
430  XOR     0       1       1       0       eXclusive OR
434  IOR     0       1       1       1       Inclusive OR
440  ANDCB   1       0       0       0       AND with Complements of Both
444  EQV     1       0       0       1       EQuiValence
450  SETCA   1       0       1       0       SET to Complement of AC
454  ORCA    1       0       1       1       OR with Complement of AC
460  SETCM   1       1       0       0       SET to Complement of Memory
464  ORCM    1       1       0       1       OR with Complement of Memory
470  ORCB    1       1       1       0       OR with Complements of Both
474  SETO    1       1       1       1       SET to One

Each of the 16 instructions above have four modifiers that specify where to store the result. No modifier means result to AC. Modifier I means Immediate: the memory data is <0,,E> and the result goes to AC. M as a modifier means result should be stored in memory. B means store the results in both memory and AC.