national center for supercomputing applications larry brumbaugh william yurcik...

National Center for Supercomputing Applications

Larry Brumbaugh William Yurcik

{ljbrumb,byurcik}@ncsa.uiuc.edu

National Center for Supercomputing Applications (NCSA)

University of Illinois at Urbana-Champaign

A Little Man Storage (LMS) Model


Little Man Computer (LMC) Paradigm

• Developed by Madnick and Donovan

• During the 1960s, at MIT

• Taught to all MIT undergraduate CS majors

• Simplistic overview of how a computer actually works

• Adheres to von Neumann principles

• Authors have built multiple LMC simulators

• See: www.itk.ilstu.edu/faculty/javila/lmc/default.htm

• Newer version to be introduced at SIGCSE 2006

• See Irv Englander text for LMC in the classroom


Little Man Computer and the Walled Mailroom

100 mailboxes1 inbox1 outbox1 calculatorcounterLittle Man

10 assemblerinstructions


Basic Hardware Components of LMS

Storage DeviceHardware Properties

ID Numbering Schemes for the Component

3 cylinders 0, 1, 2 (numbers are independent of the platter surface)

4 tracks per cylinder 0, 1, 2, 3 (0/1 are the 1st platter and 2/3 are 2nd platter)

8 areas per track 0, 1, 2, 3, 4, 5, 6, 7 (same amount of data can be stored in each area)

Platters rotate

Access arm moves over the platter surface

Data is copied to/from areas on the disk


Areas on Both Sides of Platter 0

Labeling scheme: cylinder|track|area

From 000 to 237


Physical Components that comprise an LMS Storage Device


Comparing LMC and LMS Characteristics

Environment/Physical Act Compared Little Man Computer (LMC) Little Man Storage (LMS)

historic relevance of paradigm from 1960’s to present from 1970’s to present

type of device described computer disk storage device

actual hardware location of the Little Man itself

CPU control unit storage controller

locations where data is stored 100 mailboxes (00-99);each holds 3 digit number;no ‘special’ mailboxes

96 disk areas (000-237)each holds 512 bytes;two ‘special’ areas

how I/O operations are performed read/write slips of paper read/write disk areas

a programmable device?

fundamental design principles

yes!

von Neumann model

not really?

standard disk + MS FAT


LIST Structure for the Disk

File Name Size (Bytes)

Start Location(Area)

Creation Date Modify Date

ALPHA.doc 10 006 06/03/2005 06/04/2005

X.Y.Z 5000 128 09/18/1997 06/04/2005

<blank line here>

NextFile1234.txt 0 225 12/25/2002 01/01/2004

**************20 byte names

IIImplemented as a White BoardStored in area 000


Contents of Area 001 Showing Storage Allocation after Two Files are Written

Area Number Next Area Location in File

000 007(first free area) *

001 00N(last free area) *

002 003(file continuation)


004 666(end of file)


006 666(end of file)

007 008

. . . . . .

N 666

Called Area Utilization List (AUL)


Basic I/O Commands Supported by LMS

Command

Op-Code

Processing Performed by Command

Create File 00 Write an entry in the LIST, including name, create date, etc.Initialize one Free-Area-List area to ***End-of-File***.

Delete File 01 Erase the file entry line from the LIST.Return all of the files AUL entries to the Free-Area-List.

Read File 02 Begin in the LIST and then go thru the corresponding AUL entries.An alternative approach starts in the AUL table.

Write File 03 Add data starting with the first area on the free list.Write ***End-of-File*** after the last record is written.

Append File 04 Follow the AUL entries for the file to the one containing 666.Add new records in a new area and replace 666 with new area #.


Disk Status Following Several I/O Operations

Area Next Area

Area Next Area

Area Next Area

Area Next Area

000 013 004 005 010 011 014 015

001 237 005 666 011 012 015 016

002 006 006 666 012 666 016 017

003 004 007 666 013 014 017 020

0 1 2 3 4 5 6 7

00(ROOT)LIST

AULTable ALPHA BETA BETA BETA ALPHA GAMMA

01 DELTA DELTA DELTAFREE014

FREE015

FREE016

FREE017

FREE020

02FREE021

FREE022

FREE023

FREE024

FREE025

FREE026

FREE027

FREE028


Disk Status After Additional I/O Operations

Area Next Area

Area Next Area

Area Next Area

Area Next Area

000 021 004 005 010 011 014 666

001 237 005 666 011 012 015 666

002 006 006 021 012 666 016 017

003 004 007 666 013 015 017 020

0 1 2 3 4 5 6 7

00(ROOT)LIST

AULTable

FREEBETA BETA BETA

FREEGAMMA

01 DELTA DELTA DELTA SIGMA RHO SIGMAFREE FREE

02FREE FREE FREE FREE FREE FREE FREE FREE


References[1] William Yurcik and Hugh Osborne, “A Crowd of Little Man Computers: Visual

Computer Simulator Teaching Tools, “ Winter Simulation Conference (WSC), Cincinnati, OH. USA, December 2001.

[2] William Yurcik and Larry Brumbaugh, “Using LMC Simulator Assembly Language to Illustrate Major Programming Concepts, ” The Proceedings of Information Systems Education Conference (ISECON), Cincinnati, OH. USA, November 2001.

[3] William Yurcik and Larry Brumbaugh, “A Web-Based Little Man Computer Simulator, ” 32nd Technical Symposium of Computer Science Education (SIGCSE), pp. 204-208, Feb 2001.

[4] William Yurcik, Joaquin Vila and Larry Brumbaugh, "An Interactive Web-Based Simulation of a General Computer Architecture, " Proceedings of the IEEE International Conference on Engineering and Computer Education (ICECE 2000), Sao Paulo, Brazil, August 2000.

[5] http://www.snia.org/tech_activities/shared_storage_model/SNIA-SSM-text-2003-04-13.pdf SNIA Shared Storage Model White Paper


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