PDP-11 architecture
From Computer History Wiki
The PDP-11 is a 16-bit minicomputer designed by DEC.
Addressing modes
| Mode | Name | Symbolic | Description |
|---|---|---|---|
| 0 | Register | R | (R) is the operand |
| 1 | Register deferred | (R) | (R) contains address of operand |
| 2 | Auto-increment | (R)+ | (R) is the address; (R) is incremented by 1 or 2, in case of byte or word instructions. |
| 3 | Auto-increment deferred | @(R)+ | (R) is the address of the address; (R) is incremented by 2 |
| 4 | Auto-decrement | (R)- | (R) is decremented by 1 or 2, in case of byte or word instructions; R is address. |
| 5 | Auto-decrement deferred | @(R)- | (R) is decremented by two; (R) is the address of the address. |
| 6 | Index | X(R) | (R) + X is the address. |
| 7 | Index deferred | @X(R) | (R) + X is the address of the address |
