Index register

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In RX-format instructions, the address represented has a value that is the sum of a displacement, the contents of a base register, and the contents of an index register (see  3  in Figure 1).
Figure 1. Format of addresses in object code

Where:

  • I₂ represents an immediate value.
  • L represents a length.
  • B₂, R₁, and R₃ represent registers.