PDP-11 architecture

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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