CSC 203 1.5 Computer System Architecture · PDF file• Each register can hold a single binary number ... microprogram, on other machine it ... •This level is really a symbolic form

Computer System Architecture

CSC 203 1.5


Budditha Hettige Department of Statistics and Computer Science

University of Sri Jayewardenepura

1 Budditha Hettige http://www.dscs.sjp.ac.lk/~budditha/index.html


Introduction

Budditha Hettige http://www.dscs.sjp.ac.lk/~budditha/index.html 2


What is Computer?

• Is a machine that can solve problems for

people by carrying out instructions given to it

• The sequence of instructions is call Program

• The language machine can understand is call

machine language



What is Machine Language?

• Machine language(ML) is a system of instructions and

data executed directly by a computer's Central Processing

Unit

• The codes are strings of 0s and 1s, or binary digits (“bits”)

• Instructions typically use some bits to represent

– Operations (addition )

– Operands or

– Location of the next instruction.



Machine Language contd..

• Advantages

– Machine can directly access (Electronic circuit)

– High Speed

• Disadvantages

– Human cannot identify

– Machine depended

(Hardware depended)



More on Machines

• Machine defines a language

– Set of instructions carried out by the machine

• Language defines by the machine

– Machine executing all the program, writing in the

language

Machine Language Language Language Language



Two Layer (Level) Machine

• This machine

contains only New

Language (L1) and

the Machine

language (LO)

Virtual Machine (L1)

Machine Language (L0)

Translate/ Interpreter

Machine Machine Virtual

Machine (L1)

Machine Language

(L0)



Translation (L1 L0)

1. Replace each instruction written in L1 in to LO

2. Program now execute new Program

3. Program is called compiler/ translator



Interpretation

• Each instruction in L1 can execute through the

relevant L0 instructions directly

• Program is call interpreter



Multi Level Machine


High-level Language Program (C, C++)

Assembly Language Program

Machine Language


Multilevel Machine


Virtual Machine Ln Virtual Machine Ln-1

. . . Machine Language L0


Six-Level Machine

• Computer that is designed up to the 6th level of computer

architecture



Digital Logic Level

• The interesting objects at this level are gates;

• Each gate has one or more digital inputs (0 or 1)

• Each gate is built of at most a handful of

transistors

• A small number of gates can be combined to

form a 1-bit memory, which can store a 0 or 1;

• The 1-bit memories can be combined in groups

of, for example, 16, 32 or 64 to form registers

• Each register can hold a single binary number

up to some maximum;

• Gates can also be combined to form the main

computing engine itself.



Microarchitecture level

• A collection of 8-32 registers that form a local

memory and a circuit called an ALU

(Arithmetic Logic Unit) that is capable of

performing simple arithmetic operations;

• The registers are connected to the ALU to form

a data path over which the data flow;

• The basic operation of the data path consists of

selecting one or two registers having the ALU

operate on them;

• On some machines the operation of the data

path is controlled by a program called a

microprogram, on other machine it is

controlled by hardware.



Data Path



Instruction Set Architecture Level

• The ISA level is defined by the

machine’s instruction set

• This is a set of instructions carried

out interpretively by the

microprogram or

hardware execution sets



Operating System Level

• Uses different memory organization, a new set of

instructions, the ability to run one or more

programs concurrently

• Those level 3 instructions identical to level 2’s

are carried out directly by the microprogram (or

hardwired control), not by the OS;

• In other words, some of the level 3 instructions

are interpreted by the OS and some of the level 3

instructions are interpreted directly by the

microprogram;

• This level is hybrid



Assembly Language Level

• This level is really a symbolic form for the one of the underlying languages;

• This level provides a method for people to write programs for levels 1, 2 and 3 in a form that is not as unpleasant as the virtual machine languages themselves;

• Programs in assembly language are first translated to level 1, 2 or 3 language and then interpreted by the appropriate virtual or actual machine;

• The program that performs the translation is called an assembler.



Between Levels 3 and 4

• The lower 3 levels are not for the average programmer – Instead they are primarily for running the interpreters and translators needed to support the higher levels;

• These are written by system programmers who specialise in developing new virtual machines;

• Levels 4 and above are intended for the applications programmer

• Levels 2 and 3 are always interpreted, Levels 4 and above are usually, but not always, supported by translation;



Problem-oriented Language Level

• This level usually consists of languages designed to be used by applications programmers;

• These languages are generally called higher level languages

• Some examples: Java, C, BASIC, LISP, Prolog;

• Programs written in these languages are generally translated to Level 3 or 4 by translators known as compilers, although occasionally they are interpreted instead;



Multilevel Machines: Hardware

• Programs written in a computer’s true machine language (level 1) can be directly executed by the computer’s electronic circuits (level 0), without any intervening interpreters or translators.

• These electronic circuits, along with the memory and input/output devices, form the computer’s hardware.

• Hardware consists of tangible objects: – integrated circuits

– printed circuit boards

– Cables

– power supplies

– Memories

– Printers

• Hardware is not abstract ideas, algorithms, or instructions.



Multi level machine Software

• Software consists of algorithms (detailed instructions telling how to do something) and their computer representations-namely, programs

• Programs can be stored on hard disk, floppy disk, CD-ROM, or other media but the essence of software is the set of instructions that makes up the programs, not the physical media on which they are recorded.

• In the very first computers, the boundary between hardware and software was crystal clear.

• Over time, however, it has blurred considerably, primarily due to the addition, removal, and merging of levels as computers have evolved.

• Hardware and software are logically equivalent



The Hardware/Software Boundary

• Any operation performed by software can also be built directly into the hardware;

• Also, any instruction executed by the hardware can also be simulated in software;

• The decision to put certain functions in hardware and others in software is based on such factors as:

– Cost

– Speed

– Reliability and

– Frequency of expected changes



Exercises

1. Explain each of the following terms in your own words

– Machine Language

– Instruction

2. What are the differences between Interpretation and translation?

3. What are Multilevel Machines?

4. What are the differences between two-level machine and the six-level machine


Documents

CSC 203 1.5 Computer System Architecture · PDF file• Each register can hold a single binary number ... microprogram, on other machine it ... •This level is really a symbolic form