Language of the Computer

Introduction

- Assembly Language

The basic job of a CPU,its excute lots of instructions.The set of instructions a particular CPU implements is an Instruction Set Architecture (ISA),few examples:

1) Intel 80x86 (Pentium 4)
2)IBM/Motorola
3)PowerPc (old Macintosh)
4)MIPs
5)Intel IA64

Different CPU implement different sets of instructions.More primitive than higher level languages.No sophisticated control flow such as while for loops.their design goals is maximize performance and minimize cost and reduce design time.

- Instrunction Set Architectures

ISA includes:
                1) instructions set.
                2) Rules for using instructions:
                               - Mnemonics,functionality,addressing modes.
                3) Instruction encoding.

Early trend(instructions) was to add more and more instructions to new CPU to do elaborate operations.Early trend is like “Add more To work more”
                - VAX architecture had an instruction to multiply polynomials.

RISC Philosophy (Cocke IBM ,Patterson,Hennessy,1980s)
                - Keep the instruction set small and simple,makes it eiser to build fast hardware.
                - Let software do complicated operations b composing simpler ones.

New trend is like “Less instruction But more task”

- MIPS Architecture

MIPS – semiconductor company that built one of the first commercial RISC architecture.
People choose MIPS instead of intel 80x86 because:
                - MIPS is simple,elegant.Don’t want to get bogged down in gritty details.
                - MIPS widely used in embedded apps,x86 little used in embedded, and more                                          embedded computers than PCs.

- SPIM : the MIPS simulator

SPIM (MIPS spelt backwards!) is a MIPS simulator that :
                - reads MIPS assembly language files and translates to machine
                 Language
                - executes the machine language instruction
                - shows contents of registers and memory
                - works as a debugger (supports break-points and single-stepping)
                - provides basic OS-like services, like simple I/O