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Remote Terminal Computer Graphics
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DAVID L. BEVERIDGE and ELIAS GUTH Chemistry Department, Hunter College of the City University of New York, 695 Park Avenue, Ν. Υ., Ν. Y. 10021
The dominant theme in the development of computer technology in the 1970's is teleprocessing. The interface between user and computer has evolved from punched cards and printed output passed across an input/output desk to job creation and retrieval by i n teractive terminals for individual users and remote batch entry for groups of users. Communication between user and computer is carried out over ordinary telephone lines. Large central proces sors serving local and regional computer needs on a remote basis are now common, and several national networks, both federaly funded (ARPANET) and commercially funded (CDC-CYBERNET) are oper ational. More, including a national center for theoretical chem i s t r y calculations, are contemplated. The s c i e n t i f i c community has greatly benefited from these developments. Improved access to d i g i t a l computer equipment makes possible a vast saving of valuable user time and can significant ly increase individual productivity. In chemistry in particular, scientists carrying out theoretical studies of chemical systems based on quantum mechanics, s t a t i s t i c a l thermodynamics and molec ular dynamics or experiments involving large scale data reduction such as x-ray crystallography and magnetic resonance spectroscopy have been direct beneficiaries of developments in computer tech nology. Quite often, however, the computer output generated by chemical computations is extensive and unwieldy. For interpreta tion of results one often turns to computer graphics, i . e . incre mental plots drawn by a pen under computer control or storage dis plays wherein a plot is generated under computer control on a storage display cathode ray tube. Several examples of computer graphics used in interpreting various calculations on chemical systems are shown in Figs. 1-5. The capabilities for accommodating card input and printed output as well as an interactive link with the central processor for console purposes are provided as standard equipment on mini computer-based intelligent (programmable) remote job entry termi nals. At present however, the f a c i l i t y for routinely dealing with computer graphics on a remote basis i n a convenient and economic 9 Lykos; Computer Networking and Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
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COMPUTER
NETWORKING
A N D CHEMISTRY
Figure 2. A computer generated stereoscopic view of the chemical neurotransmitter acetylcholine in roughly the geometry preferred in aqueous solution. This drawing was generated using the program ORTEP by C. K. Johnson and was used in studies described by D. L. Beveridge, M. M. Kelly and R. J. Radna, J. Amer. Chem. Soc. (1974) 96,3769.
nuta-ai-CMu
Figure 3. A computer generated conformational energy contour map calculated for acetylcholine in water using theoretical methods. The coordinates r(01-C5-C4-N) and T(C6-01-C5-C4) are dihedral angles referred to Figure 2. The structure in = IKJm Mm Figure 2 correspond to r(01-C5-C4-S) 60° and T(C6-01-C5-C4)
=
Lykos; Computer Networking and Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
180°.
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2.
BEVERiDGE A N D G U T H
Remote
Terminal
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Graphics
manner i s n o t w i d e l y a v a i l a b l e . We d e s c r i b e h e r e i n a method f o r r e m o t e t e r m i n a l c o m p u t e r g r a p h i c s b a s e d o n a s y s t e m d e s i g n e d comp a t i b l e w i t h a l l s t a n d a r d i n t e l l i g e n t j o b e n t r y t e r m i n a l s , and completely independent o f s p e c i a l c o n s i d e r a t i o n from t h e c e n t r a l site. The s y s t e m u s e s s t a n d a r d c o m m e r c i a l l y a v a i l a b l e h a r d w a r e and c a n b e i m p l e m e n t e d w i t h a k n o w l e d g e o f m i n i c o m p u t e r p r o g r a m m i n g commensurate w i t h t h a t r e q u i r e d f o r l a b o r a t o r y t a s k s s u c h a s data a c q u i s i t i o n and instrument c o n t r o l . The remote t e r m i n a l c o m p u t e r g r a p h i c s s y s t e m i s d e s c r i b e d a s i m p l e m e n t e d o n f a c i l i t i e s o f t h e H u n t e r C h e m i s t r y Computer l a b o r a t o r y , where g r a p h i c s c a p a b i l i t i e s h a v e b e e n d e v e l o p e d f o r n e t work enhanced r e s e a r c h and i n s t r u c t i o n a l a c t i v i t i e s based on r e mote a c c e s s t o t h e CDC-6600 c o m p u t e r a t t h e C o u r a n t I n s t i t u t e o f M a t h e m a t i c a l S c i e n c e s (CIMS) a t New Y o r k U n i v e r s i t y a n d t o t h e IBM 370/168 f a c i l i t y o f t h e C i t y U n i v e r s i t y o f New Y o r k (CUNY) Computer C e n t e r . Some b a c k g r o u n d o n g e n e r a l a s p e c t s o f i n t e l l i gent remote j o b e n t r y i s p r o v i d e d i n t h e next s e c t i o n , f o l l o w e d i n S e c t i o n I I b y d e t a i l s o f t h e remote t e r m i n a l c o m p u t e r g r a p h i c s system. I.
Intelligent
Remote J o b E n t r y
Remote t e r m i n a l c o m p u t e r g r a p h i c s i n v o l v e s a d d i t i o n s a n d m o d i f i c a t i o n s t o t h e remote j o b e n t r y t e r m i n a l hardware and s o f t ware. I n t h i s s e c t i o n we d e s c r i b e b r i e f l y t h e h a r d w a r e a n d s o f t w a r e components o f a t y p i c a l r e m o t e j o b e n t r y t e r m i n a l . Addit i o n a l d e t a i l s o f t e l e p r o c e s s i n g f o r c h e m i s t s have been d e s c r i b e d recently elsewhere.1 Hardware. The m i n i m a l e q u i p m e n t c o n f i g u r a t i o n f o r i n t e l l i gent remote j o b e n t r y i s a programmable m i n i c o m p u t e r i n t e r f a c e d to a card r e a d e r , l i n e p r i n t e r , t e l e t y p e w r i t e r ( c o n s o l e ) , and data set f o r telecommunication. A f a c i l i t y o f t h i s t y p e c a n be implemented f o r as l i t t l e as $25,000. A schematic diagram of the H u n t e r C h e m i s t r y Computer L a b o r a t o r y h a r d w a r e i s shown i n F i g . 6 . Note t h a t i n a d d i t i o n t o t h e minimal hardware, t h i s system i n c l u d e s a mass s t o r a g e d i s c , a d d i n g a n a d d i t i o n a l $ 1 0 , 0 0 0 t o t h e c a p i t a l investment. T h i s i s an o p t i o n a l i t e m . The h a r d w a r e r e q u i r e d f o r remote t e r m i n a l computer g r a p h i c s w i l l be d e s c r i b e d i n the f o l l o w i n g s e c t i o n . Software. The c o m p u t e r p r o g r a m r e s i d e n t i n t h e m i n i c o m p u t e r memory d u r i n g t e l e p r o c e s s i n g s e r v e s t h r e e d i s t i n c t f u n c t i o n s : a) t h e management o f i n p u t / o u t p u t a c t i v i t i e s , b ) t h e t r a n s l a t i o n and c o m p r e s s i o n / d e c o m p r e s s i o n o f o u t g o i n g a n d i n c o m i n g c o m m u n i c a t i o n s on the data l i n e , and c) data l i n e p r o t o c o l . These f u n c t i o n s a r e scheduled f o r p a r a l l e l p r o c e s s i n g on a p r i o r i t y i n t e r rupt basis. A schematic diagram of t y p i c a l t e r m i n a l software d e s i g n e d f o r t e l e p r o c e s s i n g i n a n IBM 370/168 e n v i r o n m e n t i s shown i n F i g u r e 7. 2
Lykos; Computer Networking and Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
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AND CHEMISTRY
Figure 4. Computer generated stereoscopic views of the minimum energy structure for (top) a tetrahedrally hydrated K ion and (bottom) tetrahedrally hydrated F~ ion. Produced using the ORTEP program in conjunction with studies described by D. L. Beveridge and G. W. Schnuelle, J . Phys. Chem. (1974) 78, 2064 and un published data. +
Figure 5. Computer generated perspective views of density difference maps for (top) the ground state and (bottom) the σ „ 2 excited states of Η 2
Figure 6. Schematic of hardware ele ments of the Hunter Chemistry Com puter Laboratory ca. May 1975
Lykos; Computer Networking and Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
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2.
BEVEREDGE
AND GUTH
Remote Terminal
Graphics
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To f o l l o w t h e f l o w o f e v e n t s i n v o l v e d i n r e m o t e b a t c h p r o c e s s i n g , c o n s i d e r a t y p i c a l b a t c h j o b s u b m i t t e d on c a r d s a t t h e t e r m i n a l and p r o d u c i n g p r i n t e d o u t p u t . Card i n p u t i s p l a c e d i n t h e c a r d r e a d e r a n d t h e r e a d e r i s a c t i v a t e d b y a c o n s o l e command. Cards a r e r e a d under program c o n t r o l o f t h e r e a d e r d r i v e r and copied into the appropriate device b u f f e r . The c a r d image a t t h i s p o i n t i s i n a b i n a r y r e p r e s e n t a t i o n of h o l l e r i t h code. When the c a r d s a r e i n and/or t h e d e v i c e b u f f e r i s f u l l , a f l a g i s s e t . T h i s s c h e d u l e s t h e "READER GET" r o u t i n e w h i c h p i c k s up t h e c a r d image f r o m t h e d e v i c e b u f f e r , c o n v e r t s i t t o EBCDIC, c o m p r e s s e s out b l a n k s and r e p e a t e d c h a r a c t e r s , and p l a c e s t h e t r a n s l a t e d , c o m p r e s s e d code i n t o a c o m m u n i c a t i o n b u f f e r . When t h i s i s comp l e t e , t h e d a t a l i n e t r a n s m i t t e r (DLC XMTR), i s s c h e d u l e d . The t r a n s m i t t e r s e c t i o n o f t h e t e l e p r o c e s s i n g s o f t w a r e p i c k s up t h e c o n t e n t s o f t h e c o m m u n i c a t i o n s b u f f e r , adds t h e a p p r o p r i a t e b i n a r y s y n c h r o n o u s l i n e p r o t o c o l c h a r a c t e r s , a n d o u t p u t s t h e communic a t i o n c h a r a c t e r by c h a r a c t e r t o t h e d a t a l i n e c o n t r o l l e r and thereby onto the telephone l i n e . A communication r e c e i v e d from the c e n t r a l s i t e i s processed u n d e r p r o g r a m c o n t r o l o f t h e d a t a l i n e r e c e i v e r (DLC RCVR) i n t h e teleprocessing software. The r e c e i v e r p i c k s up i n c o m i n g communic a t i o n c h a r a c t e r b y c h a r a c t e r , i n t e r p r e t s a n d s t r i p s away l i n e p r o t o c o l c h a r a c t e r s , assembles the r e c e p t i o n i n a communication b u f f e r , and s c h e d u l e s t h e "PUT r o u t i n e c o r r e s p o n d i n g t o t h e o u t put d e v i c e f o r w h i c h t h e r e c e p t i o n i s i n t e n d e d . The PUT r o u t i n e manages d e c o m p r e s s i o n , t r a n s l a t i o n f r o m EBCDIC t o code a p p r o p r i ate f o r t h e o u t p u t d e v i c e , p l a c e s t h e t r a n s l a t e d , decompressed code i n t h e d e v i c e b u f f e r , a n d s c h e d u l e s t h e a p p r o p r i a t e o u t p u t device d r i v e r . The c o m m u n i c a t i o n s c y c l e i s c o m p l e t e d when a p h y s i c a l r e p r e s e n t a t i o n o f t h e r e c e p t i o n i s d i s p l a y e d on t h e a p p r o p r i a t e output device. For t e l e p r o c e s s i n g i n the environment of another type o f h o s t m a c h i n e s u c h a s t h e CDC 6600 i n v o l v e s an a n a l o g o u s f l o w o f e v e n t s , b u t w i l l d i f f e r i n d e t a i l s s u c h a s l i n e code a n d d a t a line protocol.3 Thus c o m m u n i c a t i o n o f a s i n g l e i n t e l l i g e n t r e mote j o b e n t r y t e r m i n a l w i t h a m u l t i p l i c i t y o f d i f f e r e n t h o s t m a chines i s p o s s i b l e provided the t e r m i n a l software appropriate f o r each d i f f e r e n t environment i s a v a i l a b l e . The f a c i l i t y shown i n F i g . 6 m a i n t a i n s remote b a t c h e n t r y c a p a b i l i t i e s w i t h b o t h t h e CIMS CDC-6600 a n d t h e CUNY-370/168 i n t h i s m a n n e r . 11
II »
Remote T e r m i n a l Computer G r a p h i c s
The o b j e c t i v e o f t h i s p r o j e c t was t o p r o v i d e r e m o t e t e r m i n a l g r a p h i c s c a p a b i l i t i e s a t a l e v e l commensurate w i t h s t a n d a r d r e mote t e r m i n a l i n p u t / o u t p u t a c t i v i t i e s a s c o n v e n i e n t l y a n d economi c a l l y as p o s s i b l e . C o n v e n i e n c e d i c t a t e s t h a t a) t h e s y s t e m s h o u l d be i m p l e m e n t e d w i t h no s p e c i a l e f f o r t r e q u i r e d o n t h e p a r t of t h e system group a t t h e h o s t f a c i l i t y and t h e system s h o u l d o p e r a t e w i t h a minimum o f o p e r a t o r i n t e r v e n t i o n a t t h e t e r m i n a l
Lykos; Computer Networking and Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
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COMPUTER
NETWORKING
AND
CHEMISTRY
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end and no operator i n t e r v e n t i o n at the host f a c i l i t y r e q u i r e d . Economics d i c t a t e s that the hardware used should be s h e l f items and not r e q u i r e elaborate i n d i v i d u a l m o d i f i c a t i o n . Hardware. The device s e l e c t e d f o r our system i s the Tektronix 4010 storage tube d i s p l a y t e r m i n a l , equipped with a hardcopy device f o r production of thermofax-type c o p i e s . This i s i n t e r f a c e d as an a d d i t i o n a l p e r i p h e r a l to the terminal minicomputer. The cost of the graphic u n i t s i s c u r r e n t l y around $5000 f o r the terminal and $3500 f o r the hard copy device, adding an a d d i t i o n a l $9000 to the c a p i t a l o u t l a y i n c l u d i n g i n t e r f a c i n g . Thus v e r s a t i l e remote job and graphics c a p a b i l i t i e s can be obt a i n e d with a t o t a l c a p i t a l o u t l a y of the order of $40,000. A photograph of the remote t e r m i n a l graphics f a c i l i t y i n operation i s shown i n Fig.8. Software. The software i n v o l v e d i n remote t e r m i n a l computer graphics can be conveniently discussed i n terms of a) p l o t genera t i o n and b) p l o t r e t r i e v a l and d i s p l a y . The flow of events i n a remote graphics job i s shown s c h e m a t i c a l l y i n F i g . 9 . This i s t y p i c a l of our production v e r s i o n implemented i n the CUNY IBM 370/168 environment. To f o l l o w the flow of events i n remote t e r m i n a l computer graphics, consider a t y p i c a l batch job i n v o l v i n g the generation of graphic output using c a l l s to Calcomp type incremental p l o t routines.4 The job as submitted from the t e r m i n a l c o n s i s t s of an a p p l i c a t i o n program i n compiler language such as FORTRAN and i n put data. The job i s telecommunicated to the c e n t r a l s i t e as des c r i b e d i n s e c t i o n I I . At the c e n t r a l s i t e the program i s compiled. E x t e r n a l r e f e r e n c e s to Calcomp p l o t r o u t i n e s are s a t i s f i e d using the Calcomp Previewing Routines supported by Tektronix. The Calcomp Previewing Routines reference i n t u r n the T e k t r o n i x Terminal C o n t r o l software r e s i d e n t at c e n t r a l s i t e . Execution of the graphics a p p l i c a t i o n program at the c e n t r a l s i t e causes an input data to be read and generates a standard p r i n t e d output f i l e . C a l l s to the Calcomp subroutines generate c a l l s to the Terminal C o n t r o l Program. The Terminal C o n t r o l Program and attendent d i s p l a y d r i v e r s would i n a l o c a l graphics system manage the c r e a t i o n of a d i s p l a y on the graphics screen, a u t o m a t i c a l l y t a k i n g care of s i z i n g and other housekeeping chores. Here we intervene and r e q u i r e the Terminal C o n t r o l Program to produce an output f i l e (plot f i l e ) c o n s i s t i n g of the arguments to be s u p p l i e d to the graphic d i s p l a y d r i v e r s f o r generating the d i s p l a y . Both the p r i n t e d output and p l o t f i l e are then queued f o r communication back to the t e r m i n a l . Any code conversion scheduled f o r the p l o t f i l e by the c e n t r a l s i t e i s suppressed. A high order b i t i s added to each word of the p l o t f i l e to d i s t i n guish the contents from a c c i d e n t a l coincidence with data l i n k control characters. In the r e t u r n i n g output to the t e r m i n a l , we are r e q u i r e d to
Lykos; Computer Networking and Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
2.
BEVERiDGE A N D G U T H
Remote
Terminal
15
Graphics
READER
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Figure 7. Schematic diagram of tele processing elements, relevant to remote terminal operation. The units READER, CONSOLE, PRINTER, DISPLAY, and DLC are hardware items. Other blocks represent software resident in the ter minal CPU.
CONSOLE ft '
PRINTER
DISPLAY
Figure 8. Hunter Chemistry Computer Laboratory remote batch and graphics facility in operation. Users are from left to right Gary W. Schnuelle, Elias Guth and D. Beveridge.
PLYING
TfWNSHISSION
INPUT
[+|7ηάο»*|+ p f l ^ iEN i
o u
™i
m
RETRIEVAL
Figure 9. Schematic of flow of events commensurate with a remote terminal computer graphics job
OUTPUT
Lykos; Computer Networking and Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
PLOT
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computer networking and chemistry
distinguish the plot f i l e from standard printed or console output. The general specification of individual terminal capabilities at the central site may contain provision for any number of peripherals, and customarily IBM 360/20 intelligent terminals and their emulators are support a reader, printer, console and punch. Thus output intended for a certain output device w i l l be preceded by a characteristic data link control character, which is processed upon reception in DLC RCVR. We do not support a card punch l o c a l l y , so plot f i l e s are generated and returned as punch f i l e s from the central site. A plot f i l e received at the terminal from the central site passes through DLC RCVR to the plot/punch "PUT" routine where decompression occurs and the f i l e is placed in the graphics terminal device buffer. No code translation is carried out, since the plot f i l e as generated by the Terminal Control Package is already in a form suitable for further use. The graphics display drivers resident in the terminal minicomputer are then scheduled, and the physical display is generated on the storage tube display screen. The system as described was made operational in the CUNY IBM 370/168 environment in February of 1975. An analogous version has been operational in the CIMS CDC-6600 environment since September 1972. Figs. 1-7 and Fig. 9 of this a r t i c l e were generated on the Hunter Chemistry Computer F a c i l i t y . III.
Acknowledgements
This project was supported by NSF Grant GJ-32969 from the Office of Computing Activities and in part by a Public Health Research Career Development Award 6K04-GM21281 from the National Institute of General Medical Sciences. IV. References 1. Beveridge, D . L . , Guth, E. and Cole, E.H. in Proc. International Conference on Computers in Chemical Research and Education, D. Hadzi, ed. Union of the Chemical Societies of Yugoslavia (1973). 2. The terminal software for this task was assembled from programs written in part by Mr. Mark Ford of the Honeywell Corporation Automotive Branch of Detroit, and in part locally by the authors. 3. Franceschini, E., Feinroth, Y. and Goldstein, M. AEC Research and Development Report #NYO-1480-148 (1970) 4. "Programming Calcomp Electromechanical Plotters", California Computer Products, Inc. August 1974.
Lykos; Computer Networking and Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
