OOP S Intuitive Interfa Ace.

number of appli-
cations today

TUJE
MARTIN that make use of .
object-oriented

programming. There are varying degrees
to which the concepts are used, but in.
all cases, object-oriented technigues al- E
low the user to deal with a complex en-
vironment in a straightforward manner:
Some applications simply provide : users '
with an object-oriented interface, while
others give users the ability to somi
and create objects as well. ba

This week, well look at three exam-
ples of object-oriented programming: '"
€ Window-based user interfaces: These

are the emerging standard for comput- ..

ers, including workstations, Macintoshes
and now PCs, with Presentation Manag-

er (PM) and Microsoft Windows. ''' 4% >

€ Word processors: Powerful style
sheets let the user create complex docu:''r
ment formats with little effort. 4 4;
' Graphics programs: The creation of ,.
complex drawings is easier with object":
oriented technigues.

The most; noticeable effect of object: /$ s si
oriented programming can be seen in
the windowing user interfaces that were '

first popularized on the Macintosh. '/' Ha
These technigues are now becoming ' prt

available on PCs with Microsoft Win: "%:

dows and IBM's PM. The style of inter: ii

face was first developed for Digitalk .
Inc.s Smalltalk, the first pure object-ori:;
ented language.

The user benefits from the more intu- €
itive interface provided by object-orient-
ed technigues. The windowing interface

is organized like objects in an office. The

user can move the objects: open win-
dows, close windows, pull down menus, '
select items. The effect is the same as
opening desk drawers, selecting objects '
in the drawer, moving a coffee cup and.
drinking the coffee. Various icons repre-
senting objects are used to send mes- .'
sages to the object. The user simply
clicks on the icon to obtain the desired "
result. For example, to seroll a enojni Ši |
the user points the mouse to the scroll '

bar and clicks it. To close a window, the

mouse is clicked in the "go away" box
on-sCreen.

Visual clues are used wherever possi- .
ble to indicate the behaviors of an ob-
ject or identify the object. There are
icons for the controls on a window and
icons used to identify the applications
and documents in the system. For exam-
ple, different icons are used for pictures :
and text documents. Similar icons and.
messages are used across multiple appli-
cations. Open, close and save operations

- always appear in the same place on the

screen, whether the application isa |.
word processor, draw program or pro- '
gram-development environment. The go-

| | dows in all applications. ' ba

-ed technigues enable users to explore:«;: li ]

— technigues. '' "

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diš any more of -

away-box icon k the same. fot all kj k ' ŠE Using ii,  tetlaves V li Maepatt - Šek Nea teja KRE

styles are organized in 4 hierarchy: The, ,.; phisticated dre using object-oriented ||
attributes of each style sheet are set at.;; technigues to make it rei to create 5 Ej)

and experiment with a new envirorti: ki |,« the appropriate level in the hierarchy. pi (/ complex drawings. — UME ti

ment. Many programs čan be learned 4. Lower-level štyles inherit attributes " ;, li As shown in the figure, a paint Or 4 (MJI4

with little or no training. Once users? 4 it '£rom higher levels, and only definitions/.. draw program provides the user with (4 Y

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' User interfaces based on Object ore

learn the functions of d word processof,'" that are new, or different, heed to be ';;;;. an empty window bordered by a num-
or program editor, they then can trans: specified. "" ai Udu j? (dai tj ber of icons that represent; various
fer that knowledge to other products "" '" Www For al the basic text style in a . drawing tools. These include line-width
that conform to the same User-interface, .; - document, might define the margins, font. drawing tools; paint patterns; brush
|tBiH bligjeaa dei Maga ji and paragraph style: A heading style;;| ; ih ; shapes; erasers; tools to draw boxes, cir-;
Thus, object-oriented i terfaces help; di ' would be d subclass of the basic text. ';. 4 cles, polygons; and other special effects. |
the user to grasp and work with the ''4%/. style. It would'retain the font and mar! ' The mouse and a pointer are then used |
complex computer environment. Users ii | gins, but change the font size and add k to put the shapes or drawings on the; (4 lij gra
- learning to operate a windowed inter-; si |, the bold attribute. A progrdmming book " ' screen. These programs all use the basic. | "ine
|

opora! roka Z A — iji — Mer MI RR

Da zi na

face do so in a fraction of the time it: S nlste have a different soje for code ex- '' object-oriented user interface and em-
yploy icons to represent various options. .
-W In contrast, conventional paint pro-
/ grams view the picture as a large bit Hi ME
' map. For example, when d box is drawn 4 |//
! with a convehntional paint program, the; 44
,bits corresponding to the image are
V turned on. When a circle is drawn inter-. Hi
| secting the box, some more bits are j ii
' turned on. The program only has |
V "knowledge" of the on and off bits. Af: 4
fer the initial drawing, the program has... Hel
'no control over the circle and sguare ' zal
(and can only add or erase bits. There (ii
are copy and duplicate functions, but EKO.
V these work with areas of bits mia not. si V IE
»with objects in, the dravi Bik
One Shape at a Time en MENE
'4 Inan object-oriented drawing pro- :' 'ii' '
; gram, the shapes are remembered by | 4
' the program as individual objects. They: /'

How Word-Processlii Style Sheets Use
Object-Oriented oe

Styles Are Organized
Ina Hierarcehy

le
Po. PM nie | Pammnee

pra:

: a zi oa | a] aa, Ne a k
RA Darsa iznad RR SS
ee a E ia s NE NI tm. moti

M ba -y s ea
: ia be čer mz ašaj z s NE
- ge! . Č di a Š [ s zi
4 a se :

Level |: |
Basic Style V?

Attributes ; —
» Margins
o PONI
» Paragraph Style

|
»can be selected and modified once. .; '4iW
' drawn. They can be moved about the |, Hi ii
screen, copied or deleted without, dis- h | h ii: Uf
| turbing the objects they overlap."' ' i idi
Objects cari be combined into more ' iti LI "
S "complex objects, which cari then be ma- Hi II
|, nipulated as single objects. Complex ob-' //[
| jects can be duplicated and moved, a : ||
lowing the user to work with the ča U

Level Il:
Level | Style Plus
Additional Attributes s >
« Headiij ———— — a ee EDI — | |

pa
TE ne NE —— aaa upre, "

Level III:
Level lI Style Plus
Additional Attributes

» Subheading

— šim

(ing at a higher level of detail. ' Ii:
:;.. Each object can be edited. "Editing a ME

« line means changing its end points. The bi: O:

— same edit message can be sent to a rect- Mi

:rangle, but with different results: The ;.' [if]

z edit will change both the rectangles ; 4

m -

Ši vi RA dla ME, te E Her Ha john hvakšn . height and width. Each object responds | |);
Pb Sn ja | zRi S Hi tdi Minci,4,, to set attribute messages, but the | Ki:
Kraji, | ži bami Nice (| (a attributes affect each object: differently.

Using objectorientei teci, stles re organized ina hi ureo nino be vestni |
vu erarchy. The atiributes of each style are al the Pile KRE < auate, but, for more complex drawings, dili
h le

; the object-oriented approach is recom-
s!  mended. The use of object-oriented tech-
kal di 4 ta - nigues simplifies the user interface and |
pe | Mil KI helps the user to manage complexity. |
| 4 Co teri mi KI Ju h Next week, in the fourth and final ar-

would take them to lani a V oe antiij a rade in which aly the font 4 poo JE : ticle in this series, we will look at the '
al PC interface, because the windowing bi ' changed. All of tHese substyles inherit |  growing use of object-oriented tech- .
technigues help manage and control the: 4, attributes from the basic style, so the | . nigues to implement CASE tools and
complexity of the environment. 4"; user has to specify only what, is differ- ' |. databases.a | io

One of the more dramatic recent uses.  ent for the štyles lower ini the hierarchy. | —————————
of object-oriented technigues is in the This use of object-oriented technigues % To learn more about the subject of
definition of style sheets in some word- ,;. for style definitions results in d very "%:. these articles, please call The James
processing programs. The style sheet, de- easy-to-use interface for developing co aii . Martin Report, an information service
fines attributes, such aš page layout, plex documents. The levels of abstrac- | updated gudrterly, at (800) 242-1240.
font type and text format, for some ič ' tion and inheritance make it easy to"

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documeni that Uy
ment: might have styles for regula k, have a complex structure/ Again, objecti |', ada) Technology Transfer Institute, - ns
bulleted text, headings and subhet dings.| . oriented technigues | pe ih (741 10th St, Santa Monica, Calif. Ni ji BE:
The dli: sheets are specified by th 4, te p ment of complex . ideas. PA | |90402 (213 , 3994-8305. Im Europe, con- "li
al There are n prerano tr for pro- (| tact Savant, 2 New St, Carnforth, "| Wi! !
s" Uslne a zori Pi A poreech, £ brie pictures on d computer, begin | Lancs., LA5 9BX United K: (ooo k V
ae spro] Bl, seine | nin with, Apple Coraputef Inč's original |. (ose) 784 506... ee Um
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