t

I

‘I

Bcn’ioi IVI Z

3r

B C to 6

onGpsis:

TCs per thscnsos th areas of application and e reasons for the choice of the

or I angu e in th raining fComp ter Syste ns Engi ieering students t the

in y hno

I±itrnductiorn

I) n the as bur s there has been a significant growth in the use of the

t’o t language in tin’ training of students within the School of Electrical and

Computer Enneering at Curtin University of Technologr and in particular

within the Computer Systems Engineering degree. The variety of applications,

and the reasons for the introduction of Forth are presented to show the potential

a f tin. guag thin neen ig cducat

Th rigina lssignm nV

Th€ irs introduction of Forth at Curtin was as a student assIgnment. A major

a,signment was initiated in 1984 to investigate the language, its uses and to

‘ g t app tions oropria to coirputer syst’ms enneering courses The

ci I rerta i r avalabl a I ttimewasfortheZ8OinaCPlMstyl

dc mont °nvironn ent(CDOS)

Phe results of this investigation showed that the most likely applications for Forth

were:

1) in eiectronicJcomputer systems projects in the

hardware area and in relation to industrial control,

2) ir the teaching of assembly language programming

3 in the teaching of certain operating system concepts.

F1rst Austraian Forth Syrnposum

if -

t’ chine- ii ;naii cn/nuu

it

-

i r di. ‘0mw s i nplc. tat am orth I eon us Com

g. ue.PO SEC at urh c mdcix the cix son between IBM/PC

SON arm cIt it ix at-d Mao ntosh users vith an appronmate 50 50 split between

off user and als-- in hie studs t’ Iab,rstorr facibties

LW Forth C UR’F’( F ) for th FM/PC

LI o n

ito Is ip

in cmproces or

4, MaJi N for the. Ma mixosh

Projects

e use f F orth ii ix ergraoua tude t ects which last through the final

to i hs I i ir u & o vitis staff familiarity The

st thr plemor ons m ed ha ocen ar ar being used for project

dvelopments witb varyong deeec of success

Forth is now also being used at the. postgraduate study and research levels.

IMJFor forthelBLWC.

Jif FM/P cl bee for roe to

of en is Of a steida d notM

a&Cini Ic. improv e apphoa i of UP! OR I H fo udent introduction to the

assembly language fcr the 8086 Whilst the Forth puristt may not support this

4eveiopn eat it providos sigruficant adt antages in teaching. This project

complements the facilities in Mach II which are discussed later in this paper

der tie to ching of assembly ar guage

e latns a he p stgraduate 1ev is the development of improved industrial

c ntrol software for he vy md etnal apphcation.

2 First Australian Forth Symposium

F

c1 3 J! tuCt1tS

c Y’ w II he yr rt nu o

ti io a itt oro m 0

P aan ohr; s cn ch:ch could bt proulded vatu commana stnng a

2 2 ras d k if crc tior of indopendent omzr nd vat

r ted th ci n id g er’ a rdiobuor og or

1i’bIe text inscrtrore This project proessed to the level where a command

anp’cme flOd noveasent on three axes of the robot for each command string

n 0 s 1 s i xneuc r ru n ‘0 asp o

tee proer and in the rehaoility of hte demonstration robot arm.

b ftc. S ugle ‘hip 6811011 ‘lipmcessor

inrbe of project. at Curtin have been involved with the development of ROVs

Remote Operated Vehicles) for underwater application. The newer ROVs are

it s railer han their predecessors to cut down power requirements and to be

tao c manouverable The first AUSSIE submersible produced used an STD bus

7-80 bated system both at the surface and below for communication and control

pu ose To help reduce the volume of electronics the use of single chip

a pr css cot oilers ha beer advocated but not implemented until the

am dcx ciopmont facilities could be made available. Late last year the

s’ o’ n was mad’ that a sir gb chip microprocessor with a built in Forth could

rr ti- ac. adf ctsrcvn 1 um’m de Icp’ettrne aM fa al’tte

‘0 recuitant ase of the MaxForth implementation on tire 68HC11 is proceeding

ry sarlbfactoniy and being configu ted to implement the communications and

I c attic fa ardwtfr h ROVtef

Teaching Assembly Language:

F r ur be f y r the Z-80 assembly anguage was’ u ed e tensively withir

the Echo 1 but he advent of IBM/PC facilities and the use of Motorola 68000

orotessors xx VME bus systems for robotics, and real time system applications

h s cc o a sig rificant reduction in the use of the Z80.

ml- aced was to introduce assembly language as efficiently as possible. Once a

student has become familiar with the concepts then conversion to the specifics of

an lternative processor seems to be less of a problem Forth was considered as

C Au aha’ co Sy”posumn

--1

-K — —

o ho tact

a gu v a ab ‘nil acinto

El- ha’ teen sA 4Lpas r ts attito ergraduate o

cm at dimna himj to teo-ih ‘en Ty language programming for the 68000

rocecsor results ham been sec one imaging In effbct the students are

tea H-g two1anguages at onec hi’ - thm does not appear to cause any problems.

I e debugging and tiace facilitu allow the students to quickly relate Forth to

er and ‘stand t of ntacr i itions t £ ate inline code

feq xl he and e e concept of

ME d p he I mph. to o provides

ents wi obviou derstand hi xamplcs of ‘tack frames,

bonmquently it has been found that the students can easily relate to the procedure

linking requirements -of other high level languages such as Pascal, Modula-2 and

o with which they are familiar i beneve the development of a “conventional”

assembier for Forth implementations on the IBMiPC could open up wider

educ tional markets for these prod cts This ha resulted in the current

c duate r j to impi is feat

ri eking (Mncepts

I g multit sk anu tea tents f neers I ge xally beer a

onerous task. T school rot s ow eats used a “—al time exccut1u for the 180

from Kadak m Canada nhich was med both for teaching and project application

Other fac’htes used mcluue Versadus and OS—9 for the 68000. a stmpler iearmng

mvmnment ‘va deOreanre whoa aitag “ito the operating system principles

ar I en allowing r ‘mIle imple atic us to b ed in real ti ne applications

pts o l. vitching hi nmux to needed to be presented in

£ rmngenvi oxiner Vi hs rae vi gva gsbeoause fitsroundrobinr e emptive task swmtchirg £ nhg atior a I Ii was used as the

ni ut asking learning tool and with emphasis n its limitations an important

part of the study process. The students using Mach II for this process had

already become familiar with it through the assembler studies.

A combmnation of lecture and assignment were used to get students to face up to

First Australian Forth Symposium

rp I

Ire acL:t S’ft, 1Qict’a a

lit tiw tardard sh:d4ier ifl Mach 1 with o priorti

C o e r s t ts r i

N It pen

‘:1 chol lia just purchased a UMI robot from the LK which xs programmed a

a on c Forth 1mw an mM/Pc-me Rfl” teach eackage ror the robot is en

p ic io lay r nit n p o an b3star at Forth sP a, h novem nt of

tho robot axes may be directly controlled by single keystrokes on the keyboard

a g r o e ar e aunerickeypad area.

Forth words have been defined to set and read the control parameters of the robot

to th r v th ords which ‘ontrol a learning mode give considerable fleñbility to

sw em connguration.

Thts ;s adding considerably to the appreciation of Forth as a practical language

fo use n the adus nal control field.

Coc io

The application of Forth to the traimng of engmeenng students (specifically

Co ipu er m Fag ne dn studer ts) I as grow a quite dramatically during the

las (ncr yca”s simly P ecause t cuts ±e desigu panc pie and systems

rquirnments ‘ithn the n urse. It is ant.cipated that Forth will continue to prove

to e ig fic t acto ir h ra urgpr gr an bocaus of tseasylea air

Cit n’actenstlcs and its simple access to the hardware through assembly

Toe avaiiabtiity of small industriai robots configured and controlled by Forth

u on tar ds v ‘11 farther enhance ts r pplication to a broader spectrum of

engineering studer ts,

rs Ms iT’ n F ft Syapostum S

CK IND

o Fca

0PE HiLLN.SJJA’!STPSjLIA

928 6.

I 3OLLEGE‘2 FORTHAPPROACH TO TEACHING

SESSON2 SESSIIENT ,* D

3 P SYLLABUS1 FEEL FOR LANGUAGE AND MOTIVATION

3 2 VARIABLES AND CONSTANTS33 LOOPS AND TABLES324 EDITOR AND FILES

5 DECISIONS - 8

3 6 MOVING DATA7 DEBUGGING S

328 PORTS MUSE AND 0803 2 2 2 8

39 PECT AND QUIT 528228*85

3. O COMPILATION 5 2 5 2555252

3il N/C LANGUAGE 1 2 2 8 2

12 N/C LANGUAGE 2 8

3 FRD(RE I14 RDUARE2 2 5

3 15 ‘RD(RE 5 8 5 2

3I6 MULTITASKING S

3.17 METACOMPILATION 2 2 2 2 2

4 GENERN COMMENTS 2 *

GG LNSITOR

0s2 FORTH53 COURSE

5 EVALUATION 2

6,tA S

7 KM DGMENT

S I5 3

3344

5 48 58 5

5566

5 66677

2 9555 25*5 9

95 85*888 10

8 101111

I

*7

I

5 788

First Australian Forth Sympos!um

a ‘a ate ‘

t r f fa e’ a1 Nr t nay C’ I e I C

nt e t cc c q; ice -ng

o a çjouerment tertiary adu at çr ‘at ti t

+ r c’ies I over’ he ‘at te Its ‘at de ‘a ar ‘a ‘at y bgh

a cr They g duate after 1/2 aears of full time

i are awe ded a crt ic te a t e ak 4 e is r

ge S’me o the graduates are accepted and proceed to

ati’utes of higher education or univers ties

At th moment undergraduates in the digi tel strand are

fced among other subjects M/C language programing for 2 CPU ‘a

h 65B2 for beginrers ir stage three followed by an advanced

(,2 ‘ado- POF Lor the final stage 4 In the advanced 6502

nre students are encouraged to build theL ow hardware and

a t i te rupt driven software to control I/O peripheral chips

r e oftae is buried in Eprom Until h ‘a yea BA°IC was the

up’, available high level 1anguage

Participants to the FORTH course come from he electron c

:noustry and have as a minimum prerequisite a certificate in

Electrical and Electronic engineering or equivalent

qu&ification Some are Institute graduates Participants’ ages

vary from 22 to 55 they come from the private sector

government and government authorities eg WATERBRD CSIRO

AF3C DEFENCE SCCetc Most are experienced in testing and

building electronic equipment and are hardware oriented but

Keyboard experience among them varies Most of them have it

s’orr programing in BASIC many from programming the 6502 or the

78P and others the PDP11

The Forth course is free but the cost of books software

aid hardware i born by the part cipant Attendance is 3 hours

per week for 17 weeks Of the eight groups who have attended the

c urce so far 3 groups were released by their respective

employers to attend day time sessions the remaininci 5 groups

a tended evening sessions starting at 630 Pt1

Motiv ton cried from the need to assess and catch up wtb

e softwar t chnology to the premise of effcient hardware

nrtrol‘Th ‘a he participants within and between groups are a

+ xtu uf widely di ergent i erestc a d experences

Ther is an ongoing discussion among staff at NSCT as

to th p rpose of teaching software subjects in the School of

El ctrica Eng neering Though staff agree that it is a mixture

of data acquisition , processing and display modeling, problem

so yin9 and the control of hardware they disagree on the amount

of emphasis to be placed on each component but a trend has

emerged emphasizing in our School the control of hardware

1 0 g h I ij FF ac Je dee ger na d 0

4 L LOU 05 tut ne avaiabiea t cou o 7a out bø an+rar

T °DP 4/c as ce 1e niy n r puc and ona e m S h k v we

a 1 e ore er ny af em are th ie ha or

o unknown quantItY and no° n the main st-earn of tings

The breakthrough occurred n md 1985 when 3 events occurred

muaneousi? and renforced each other. NSCT acquired 15

-i con ute a r irg und MS dos The 6502 Rockwell Forth

p ha up cc cc I ava able nd Sdney

p vioc the puu’ c i er on Le. en Per y L&P1

F83 With scarce funds available for the purchase of software the

L&P version of Forth was deal in many respects. NSCT did not

ave to worry about distrbu’ion problems and copyright

ri em n s an d nt I si of &P a ava lable for 280

s owned y rraiy o ou tude ts the source code of the

anguage is available and fully documented echrically it is

robust and above all blessed with a metacompiler.NSCT distributes the software at cost price and in the

a irit of FIG,tn Febr”ar” 1986 NSOT e Ilad the Crst Forth group . In

u y 1986 12 staff members att nded an 8 week 3 hr/week Forth

course In February 1988 this year the 8th. Forth group was

enrol led,Though students experimented with RSCForth on the Rockwell

c ip and Br te Forth on t e Ir ci 8051 ontroller there was never

orma p act al ab wo k tudeits to ght hardware kits late

the course and experrre te it thee according to their own

fkeld of interest.Earlier this year NSCT bought Inner access Forth for the

Zlog SuperB chip. It is now NSCT’s adopted hardware chip. It

ns a 20 ‘lHZ ard t s ftwa e is den cal to L&P . Its price

w b n the a f de h aid of the

tacorpiler app ication e ne n e oe ‘lSCT has acqu red

Maestc boards with the NiX chip to demonstrate and experiment

with the latest in Forth techno!ogy, Twice hand robots borrowed

froa the School of Mechancai Enginee ing schoo1 were programmed

se a ort e as u d e x o ks ‘laster ng

th y A derso ar Tra , he eco d ed ior of StartingForth by Leo Brode and Forth A Text and reference by Kelly and

Spies. All excellent textbooks for beginners though the latter

goes into more depth Stude9ts are advised to read chapter one of

Bode aT nkingFo h

F’ AusI aNan Eorth Sympos urn

ci r e b K a b

Each tudent has hs own Air icot cowputer he ma. imu

njjer + etudents is 15 per class. As Forth theory is developed

e tudent s imeedi tely requested to test his understanding

t a e f e a. e e eyboa de 055l C

aa.les are chosen ta have a v sual ard audible impact

Theoretical exp1anaton never exceeds 15 minutes Thus a student

cutt1e between his desk and keyboard around iø times in a

5 sc n he beg nning of the course b spert more t e

a tSe keyboard as the course progresses.

In every session a set of notes is given to the student to

omp ement the textbook material or to emphasis some point. At

e eg n g he ourse the studen purchase at ost pr c

be L&P Forth ersion modified with a screen editor. The cost +

the floppy is $5 . A similar version is available for those who

ave IBM’s or compatibles.

2 Z ASSESSMENT AND AkiARD,

Assessment is based on an end of course test weighing 20X of

be ourse marks, 88X is devoted for yearwork assignments and ab

tasks. Students must attend at least BOX of the 1? weeks.

Successful students are issued with a letter confirming

t da e an u e . ctatemert of attainment, Uni c are

)t wa ded

s P s a tor Sy p siur 3

F

t S.

i th s f t week we stress the ‘act that Forfl is

ike a spoken cr yr tte Iaguage Spacec o gaps must exist

betw en ods Tn larguage is a d ctonary of words grouped into

‘ffeent vocabularies, he ci io ay s e s cc’ ased by

$nvetig or creating nw words

Wh feth s cal’ed a threaded ‘angage he . treads nf

L&P and the hashng of it

The cortrol of VDU and cursor AT, DARK dEEP , HELLO

Inventing rew words us rg Id on The reamig and

FORGETnng of definitions

Strings Positioning of strings

The data and return stack,

Dot and EMITDelays using MS

Changing Radix numb r system

Tynical examples

0, WORDS, VOCS,I HELLO CR HELLO BEEP

2 : MY—NAME—IS John Simpson * CR CR BEEP ;

3, DARK 30 20 AT MY-NAME-IS 200 MS BEEP 5 TIMES (LOOPS)

4, MON-NOtI MYtW*—IS ; (Frerch)

5, FORGET MY-NAME IS

6, 12 HOC CR 12 DECIL CR

2 VARIABLES -N YS PFT

C ONSTAMT SChoosing rarnes fcr crnstants,

VARIABLES, A ot of ime is spent mar ipulating variab es

c a fu damentl oncept to Fo th

ar ab e a 2 byte storage area

-t is ar addrcss of n r yg

t is a system variable,

etcr aid store data,

fetch ard store a byte,

System Var ables, BASE ot the Forth System

PRINTINO ON,

bk’JING OFF,

i First AstraIian ForM Symousium

cc set K ed n ‘he fst week a ng IMEC

e op c n cc ntere t p shet tn loop ndex I is

cL nej 14 h U R UcP 1D , UD ASCI1 and EMIT

Pr r of Jet1iial/hex , decnal bi ry and AS II ab es

Neted loops and LEAVING loops

lnt’oruction to the screen editcr

Hog Supe S hardware kit

Orgar iz Uor o hcrdware proiect

4 EoI3P AND FILEc

Screen cdi toreEditor commands Help menu Shadow screens

torth filesCreating and Opening filesg

Copy and Convey of screensa

Loading sc’eens Emptying dictionary

I ne skip and screen skip

DEC SIONS

P rt flags CPU flagc

KEY and KEYIF THEN and IF ELSE , THEN

Nesting of control constructs The use of KEY and KX?

e th r control conctructs.

it for a coon definizion

Stri gs: C

‘ sitioal case statenent (best cace statement)

n K3VI C DATA

T is s ne of the most visraV sessions most effective

and most in erestirg

Ar rays are created , blanked erased and 4 i lied then

twpedData is moved between arrays

Data s fetched and stored fran within arrays

Data from 1024 size arrays is updated and flushed to disk

Blocks fran CON and HEX files are fetched from disk into

RAM, manipulated, then stored back nto R#*h

Memory is DlJ1Ped

F’ A sV”Iiar Fo1b Syrnoos;urn11

EU’ 3D Fds ar

deade f r da a [ aderK7DE and PEJ$L,<ECURSE RECUR F

Cl Fl exam os

r

°crt v/s memcryCetcb;ng and s’orng data tron and to portsProgranwn g r 4 channel zround chip ( TI ) ia a serial port

Tr at kin) d do bI umbe sP air a ib bt i cc port tenavalabe

W de n est Boa Speed NOVIX IBM

30 EXPECT A-ND (iflT

EXPECT3 PAN r I vOuter i a pr e 00Coand ne i terpreter IN ard D0NE?Keyboard and d;sK intenpretationtWIT TWES as examplesVec’oning the nput wod sourceEVA ( nV ron on)

3 rflp

cwrra C orraa and untrralThrpiiat’on al d:tferent constructsE r in n c i on ack pt har e

Jr3 r6E

808 and’ tectuneI uc ns

s orth agsSimp e M/C language routi es CODE NEXT ENDCODE

MSDOS interrupt cai’s

First Australian Forth Symposum

3 UJ C

i a. ii rctrtct4reC :nrd!t ore. S

C rC:C yn ue ow hei todcies 2The Laxon In ck

r r e‘Exit R )RCP

‘J 1nt

liloq ¶,upere C p ar hitecture

n r t n seZHog interrupts

tiardware proJect

2 HARDUciPE 2

ov x chip ( chitectu’eInstruction setHardware proJect

2fl5 HRDURE 3

Nov x op imiseHardware proJect

a3 MLkJ iT3SKiNO

o d o n u t ta krg o p Pause

User variable and syten variables anea

Task creation Task wake and sieep Background taskS

ingie and Mul i

mul - ask e amp e de o st ated

Hardware projects

* METACJMPILATION

iemeaiCngofmetacnpilation.

-e mechanics of metacompUation

Metacompiling a headless appiication

Firalizing harckuare project.

NOVIX metacompilation

FtC Astra’iar Forth Syrnpo&un 13

- ndvt

S --- €. ‘ -aeriL sta’ U€L t

I t a h€ t t ‘ of cx r n te’ a

0 3 C 1 C 0 0 t P

ar o - at urunpntaton n

u o- a cua e t t g r

otr p a &Jcr0 a boy fi rton wch can sidetrack the

-at ur But ulta’-’ ‘ n or the sr-ous student a gold

+ -f t r r ttp )xrnmr tchiqes, opc

at 1€ a ‘ ic a 3 e cros wt ct t on us beg inc’s

and oracttoner alike until understood that is are meta

c-rper worth s at e’ a itun the her el86b1k But after L&P

o [ 1 s r th c ag i

No dft:o1ty ‘as been experened ‘n handling arthmetc

an logic operators :r poatfix mcde beyond the normal

r a o a g + 4 € c a en y st p ol t ns

c simpia prob era are de beate1, undetaker to demonst’ate how

a word representing the ‘na1 solution is made of simpler words

Th r cessi y + do umnt ng th t rf cc between words thru a

co d’ a ac d agrar i s e ce t derts are advised to consul

Leos Brodie Thinking ForthBeg nrers tace 4 types + difficuities Clerical

eGa ca c cia adge i rh

lerical d+ficulties are due to the novelty of Forth

insertng a space between words is usually forgottena specially

• or d fter o cn a c o a d ot quote Forgetting to

terminate a de irit on w h s mi olon Not pa ring IF THEN

IF ELSE THEN DO LOOP etc and incorrectly nesting

tb n A so fo gett ng to tic t’ieir orly in ide colon definitions

cc ar ca f c a a te se o the edito and th

handing of fles The firs4 time I introduced the traditional

i1e dio I reaized that c’jdents were hang dfficuities.

t ou d o a re i € t e a o t • •d tor and Forth A

clear demarcation between ed t node aid For th was necessa y, A

ecreen editor was impiemented It is a must for beginners But

n he t • cree edit r a a Ic rn ng cu tie

‘ic ia d nj o + € i r t ot ho th ea ing a d

operngot ties. Moving bockswih>r and between files

Ircidena difficulties a-c due fi the flecessity of learnng the

88 t n € ad osn a e orde towite low

lee1 rorth words This is repeated 4or the Zilog SuperB CPW

Genuine Forth difficnltes n ascending order were

BEGIN 491 E REP!A The flag + WHILE ?

nterp e at on an comp lati i

3 Imedate words4 4ORD How come WORD usage c infix ? its input is

from nput a ear tack ‘

5 Deferred compilat on6 CREATE DOES>

1 4 First Australian Forth Symposum

t r ie EbTT3R a :oftwa c w &c h n en

t a e it a c g h

er d fa ‘I t> o a scr en be we st g i t d k ir

aee of error an appropr ate message i displayen The:;stuctor wLl save hmseIf quite some effort in the first few

e t t t d t a e oF h

cdi ts

The cdi tor s to cPeck that the fol ii ng words are:

d V e b a

F

I e by an and

3 Paired: DO LOOPIF nnn ELSE nnmTHENBEGIN AGAINBEGIN 1NTILBEGIN WHILE REPEAT

Sof wa e ci h to fH er out the Liput of

cotr c aracte s v a keyboa d2 Disable unused keyboard keys eg Up arrows

3, Provide Video and Sound words egt[ C n ) generates d o4 f eqen v r,

do Re EXPEC to accept on y numbers as nput

5, Read and write ASCII and hex fles at other than

on 1 Kilobyte boundary,He f ci t like VIEW bu mo e n he attire f

i t a ardtowt

‘ O RE

-he topics of th,s tourse a outl ned should be sp cad over

2 semesters with more time spent on harare and on problem

lv ng te nique A specif c set of abs ard a pr ject should

de a ei e art c pan s

S2 0 S r ur

td t f. çf. - y t tuoent e

t of c e c s No erorgt ef r was

nCraw ro cc rue: di o lac o e b t

e a o :o:su o s BRODIF Thinno

hRut orsoer the folow og a Th oe semester students

a r d a ev Ia g ae ard as etled fortt omputer Kit using

i e c tte many roces or av able tey g n r t d a u nRc

picaton They metacnpaied ther own Eorth program They

o e s a h n a g o o t i s h n e 8886 nd h

ZogSuper8m’xing twizh hgh eveI Forth. hey executed

M—DOS nterrup4 calls and ga ned an insight r the working of an

ore a rg syst m a d a mode n I njuage

The conf dence and knowledge gained by such activity is

rr ieable tsl o vts hatth hasbee chieved’nl

semester in an E’ectrcai and not a Computing achool without the

traditional backup of prerequste and corequisite subjects

a a I ble a the udergraduat leve reflects on the intrinsi

mer t of the Forth Language itself Forth is an effcient and

pot n education tools Reirfo-cement s ever present and

instantaneous wteher in the form 0+ reward (oR) zr punishment (

or crash) The final software/hardware product is quickly and

eas ly ea ze cay nj o tine for boredom to set in or cause

for d sheartening There is no constraint imposed by form

Crc tvty is not histracted or stifled it is liberated

Bone students have exp ess d the r desi e t attend an

advanced follow up course It was gratifying to find out that an

o g n zat r hay ng f h i pe s n e attend the ourse last

semester followed it up by sendng 4 more during daytime this

yea Our School has offcially adopted the subJec4 which can now

b offered awwherc n t[e Stat T e opt tor is he o

,ntroduce it at a ater time as an undergraduate subject Plans

t r a i e r t n i e 2 d o r e or b NOV X chip hay een

discussed at NSCflAt the moment PASCAL s otfereo in stage 1 Following the

I a se y o t o h 9 9 n be off - d or em n

sta t nq rext semester BASIC is beirg phased out Aware of the

p t r I of For h a n ° uc t o ol ard as a h rdware tool I

expec t to make fu tier ir n Ilabus a early

urdergraciuate stages

6 irct Austral ar Forth SymposlLrrl

kJJJEr. MEhI

It is no easy task to introduce to an inst!tution

onerva i e b a u e th a es abi shed c r i u uii and set o

subjects tte notion of experimenting with new ,untried and

u conuntirn I ideas That I was encouraged to do so 2 years aon

is a credit to staff who backed me up at NSCT That decision is

today fully jusUfied by the advent of the NOVIX chip and the

news of accord sou c ng by Harris scm conductors on the high end

of the market and the availability of Forth for the Zilog Super8,

t e Ii e 88’I ard Motorola 68HCI1 on the ow end, by everts ike

this Symposium and class attendance.

I uld I ke to thankJ0Haines,J Goulding and 8.Webster t

NSCT for their unqualified support during the last 2 years

T Rofe and P Tregeagle of SYDNEY FIG for their help and NSCT

Forth students for their help and enthusiasm which made the

effort worthwhle, L&P for allowing us to share a masterpiece and

CMoore for creating Forth in software and hardware0

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eveaopwer.t 4t S.A IT and the flo.z] f Phys:caj Sciences,

ilanders Ur”ersa’y Many points ae ‘a raised and it was clear

that, a.thougsz many stt4erts were computer literate the

disciplires of problem solving were inadequate The lace of

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a g an e as o v n ii’ c cx c v C obo or Pane L

.be ‘or ne in c’ainw’;L at the prodocbvitv of Forth aver other !anguages, For me the best eature of

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mini ban’ y. I ned a ri in b exb ‘nd con”der bet ‘wih ‘at ka e to “peed hoe chasing bugs

o z in g do n

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‘ou are unhap y with the spend of some part of it some of the Forth words can be recoded in

a” I e ensil (I a ive Solutions have said that taos of the importan Forth words in the

kerncl have already been coded in assembler and I have only used assembler in lv o programs, Fields

and Hooke’s Law, in Fields 1 achieved a big increase in speed but in Hooke’s Law it was probably

not worth the effort.

A disadvantage to using MacForth is that it is supported from the U.S.A. but if you are prepared to use

the telephone at five or six in the morning then they have a telephone hotline available for an hour each

clay Support is mainly offered on CSI Forth Forum on Compuserve, an electronic bulletin board. I

vould suggest that you do not join the National MacForth Users’ Group. I sent my money in March,

98 and, to date (April, 988), have received absolutely no response This group is independent of

Creative Solutions.

I c iacludc he e a nu nbcr of a cc dump showing most of the programs which have beer

cv loped using Forti. Al included a very quick outline of the method used to get the end result A

umuer o monographs are available which include the Forth code and highlights of the methods used

,n .oore detail,

Sticking

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PROJECTILE MASS456 a

TARGET MASS2345678, 1

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Inginaily this motion was achieeci using the toolbox region procedures to calculate the new areas todraw and undraw, as t would be entirel’ unsatisfactcry to draw and undraw the entire masses because

of Lb licker obtained. The effect obtair d us ig the regio i method wa easor ably satisfactory but

tar on wa. change/ ta b Emap ietho’ w’uc1 w’ r ticeably bate.

File

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I TROLLEY 1ASS RtCK IIASS123456789 23456789

23 56

gain a bitmap method is sed” e T e trolle) and brick ire act ally stored ‘n memory in the same

itmap but clip regions are u ed before kopp ng, tr Ir w ca’ o then’ separately The trolley bitmap

as a blank area six pixels wide behird the Li’ hey This is used o erase the previous trolley on the

screen since the maxirnan’ rasiance Liit the trol n’ is mosed at onoc is six pixels

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T e car ion II s bee dra ii in MacPaint and is stored in the resource fork of the application (On th.

ar app 00 ns sts of two parts, the code par and the resource part) I is copied to an

of screen bitmap at the boginning of the program It was found, that to actually draw the spokes each

ame was too slow, and so 66 small bitmaps were set up with the spokes in different positions. There are

6 different positions for the spokes of the big wheel giving an angle of 5° between each position of the

s okee nce a rotation of 1800 will bring the spokes back to their mitial position. Similarly there are

o dii Ic cat positions for the small wheel giving an angle of 6° between each position of the spokes

a File

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,1rhefl a ousedown e :ent is detecte-d in either the storage or the carrier areas, and a mass is present,

11 arro cars’ r is changed to a mass cursor and a mass is undrawn. Each of the masses are separate

cgions Th carrier and spring are drawn to an offscreen bitmap before being copied to the screen

Originally the entire spring was drawn each time the spring was extended or compressed. This took

about 21 tickcounts (2 1/60 second) to draw the spring. It was then changed so that only one and a half

oils need be actually drawn and then the whole coil was copied four times to complete the entire

spring. This procedure reduced the time to draw the spring to 8 tickcounts. It was then decided to code

this up in assembler and this further reduced the tinie to S tickcounts, Whether it was worth the effort

to code it in assembler is questionable.

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ifl Pressure Volume the masses are added to the piston region when they are placed on the pressurevessel, making only one region to move. This region is moved by drawing and undrawing the essentialparts only. The drawing of the gas molecules has been set up as a background task. The speed of thesemolecules varies with the temperature. In Pressure/Temperature the flickering flame has also beensee up as a background task, The flame consists of three bitmaps which are alternately copied to thescreen. The height of the bitmaps, which is determined by the temperature, is controlled by using oneof twenty clip regions. Floating ro’t arithmetic i used when drawing the graph inPressure/Volume.

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I e car ii diagrams were drawn ir MacPaint, s red in the resource fork of the application and copied

to a bitmap at start up

The graph is kept in an offscreen bitmap so that screen updates can be made of this area easily. This

a olds having to ‘remember” what was drawn on the graph and to redraw the dots and lines each time

A bitmap of the blank graph is used when clearing the graph. This is done for speed reasons since

memory is not usually a consideration nowadays.

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he charges are drawn onto the screen directly as well as to an offscreen bitmap. The field s drawn tothe offscreen bitmap, pare of this bitmap is then copied to the screen after the charges in this area areredrawn, The field force vectors are ctosed in arrays and, therefore, updating the screen is very quickw ien another charge is added and a large number of charges are already presentWhen this program

as originally written the screen drawing for twelve charges took almost three minutes. This waseduced with some optimisation to two and a half minutes, Two words were then coded up in assemblerid thc drawing time was further reduced to around half a minute A very acceptable time and welloih the trrc pent learning assembler

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