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CDA 4102

StructuredComputer Architecture

Abhijit Pandya, Ph.D.

Professor

Department of Computer Science and EngineeringFlorida Atlantic University

Boca Raton, FL 33431

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Introduction (Chapter 1)Introduction (Chapter 1)

READING ASSIGNMENT CH2 (2.1-2.4)

A digital computer solves problems by carryingout instructions.

A program is a sequence of instructionsdescribing how to perform a certain task.

Machine language is a limited set of primitive

instructions. They can be used by people to communicate

with the computer.

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Introduction (Chapter 1)Introduction (Chapter 1)

PROBLEMS

We want the machine language to be verysimple

so as to reduce the complexity and the cost of electronics

tedious for people.

We want to make it convenient for people touse the computer

=> complex electronics.

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POSSIBLE SOLUTION

the built-in machine language is L1 but is

tedious.

So form a language (L2) of instructions

that is more convenient to use by people

How can a program written in L2 beexecuted by the computer?

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TRANSLATION

Replace each instruction in the L2

program by an equivalent sequence of

instructions in L1.

The new L1 program is then executed by

the computer.

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INTERPRETATION

An L1 program examines the L2 program

instruction by instruction.

Then it executes the equivalent sequence

of L1 instruction directly.

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TRANSLATION

VS.INTERPRETATION

Similarity

Difference

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It is convenient to imagine the existence

of a virtual machine whose machine

language L2.

L1 and L2 must not be too different

=>L2 is far from ideal for mostapplications.

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Invent another set of instructions that is

more people-oriented.

Call the language formed by this set L3.

This can be extended to as many levels as

needed so as to make it convenient for

most application programmers.

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We are mainly concerned with the

concepts and techniques of constructingmachines as a series of levels

We also need to define the details for

some important levels.

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WHY STURCTURED COMPUTER

ORGANIZATION?

Viewing a computer as a hierarch of levelsprovides a good structure.

It is a good framework for understandinghow computers are organized.

Designing a computer system as a seriesof levels helps to ensure that the resultingproduct will be well structured.

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HISTORICAL EVOLUTION OF

MULTILEVEL MACHINES

Two Level Machines : (1940)

Conventional machine level

Digital logic level (complicated)

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Three Level Machines :(1950)s

Conventional machine level

Microprogramming level (limited instructionset)

Digital logic level (reduce the # of tubes)

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The programmer has to operate the

machine personally.

To run a FORTRAN program the

programmer had to do the following:

Read in the FORTRAN COMLIER (CARD

READER).

READ in the FORTRAN PROGRAM

(CARD READER).

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No errors => the complier successfully

translated the machine language

programs punched out on cards.

Errors=> Correct them and start all over

again.

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Read in the machine language program

and the subroutine library deck (card

reader).

Execute program.

Errors=> find them, correct them and start

all over again.

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FOUR-LEVEL MACHINES

(1960)S

O/S level (automate the operators job) Conventional M/C level

Microprogramming level

Digital logic level

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O/S got more sophisticated

=>new instructions facilities and features.

Some new instructions are equivalent to

conventional m/c language instructions.

Some different (i/o instructions)

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BATCH SYSTEMS

Time-Sharing (1960)s

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Hardware: tangible objects

Software: Algorithms and their computerrepresentations (programs).

Firmware: Intermediate form betweenhardware and software

It consists of software embedded in electronicdevices during their manufacture(microprogram).

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Hardware and software are

logically equivalent

Any operation performed by software can

also be build directly into the hardware

Moreover any instruction executed by thehardware can be simulated in software.

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Process

A program in execution.

At any instant in time a process is in acertain state.

The state tells how far the process is in itscomputation.

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THE PROCESS STATE

CONSISTS OFAT LEAST THE FOLLOWING

INFORMATION.

The program.

Indication of next instruction to be

executed. The values of all the programs variables

and data.

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STATE VECTOR IS THE GROUPING

OF ALL THE CHANGEABLE PARTS

OF A PROCESS:

The effect of a process is independent of itsexecution speed

If a process executes again with the same

data, it goes through the same sequence of

states and gives the same results.