created: 07/30/01; revised 11/09/01, 10/25/02, 03/16/03

# CHAPTER 21 — The Extended Assembler

The basic assembler creates a view of the processor one level above raw machine code. Instead of using bit patterns for operations, operands, and addresses the assembler enables you to use symbols for each. However, each instruction for the basic assembler corresponds directly to one machine instruction.

The extended assembler creates a view that is at an even higher level. It implements an abstract machine that has a much richer instruction set than the actual MIPS hardware. Many of the statements that the extended assembler accepts correspond to several machine instructions.

#### Chapter Topics:

- Register mnemonic names.
- Pseudoinstructions and the pseudocomputer.
- `move` pseudoinstruction.
- `li` pseudoinstruction.
- `la` pseudoinstruction.
- `lw` pseudoinstruction.
- `sw` pseudoinstruction.
- `nop` pseudoinstruction.

SPIM can act as either a basic assembler or an extended assembler. Previous chapters explained the basic assembler so that you could see how actual hardware works. This chapter makes greater use of the extended assembler features.

### QUESTION 1:

(Review:) What is a general purpose register?