The basic assembler creates a view of the processor one level above raw machine code. Machine code uses bit patterns to specify machine operations, registers, and addresses. In basic assembly, you can specify these with symbols. 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 accepted by the extended assembler correspond to several machine instructions.
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.
(Review:) What is a general purpose register?