Systems Reference Library IBM 1130/1800 Plotter Subroutines

SCALE
The scale subroutine accepts and stores scaling
inf ormat ion required by the grid, plot and character
functions.
I f the scale subroutine Is not c alled, t he plot subrout
ine assumes init ial scale values of one inch per
unit along both axes and establishes the origin
(intersection of the X axis and the Y axis) at the
present pen position. Howev er, t he scale subroutine
must be called to define other scale factors and to
establish the origin at other points. T h e scale subroutine
can be called as often as required to redefine
the s c aling values and the origin position (see
Figure 2).
Desired Scale: X Direction: 0 . 2 5 Inch Per User's Unit
Direction: 0 . 0 5 Inch Per User's Unit
(Not Drawn
= T o Scale)
=
• =1
,
• =
Chart Paper
i I
= Present Pen
(-5,30)
Up
Call Example (FORTRAN):
CALL SCALE (0.25, 0.05, - 5., 30.)
X,Y Scale Factor Pr esent Pen Location
(Inches Per User's Unit) (User's Units)
Down
User's
Units
•
+X
+4 —
+3 —
+25
+I —
t i l l t
-I —
-2 —
-3 —
-4 —
-5 —
Desi red
Origin
-25
l - V
Paper Movements P e n Movements
Figure 2. S c al i ng and Origin Location (Example)
Left R i g h t — . .
FORTRAN
Standard precision:
PLOTTER SUBROUTINES
NOTE: E a c h time the scale subroutine is called,
the origin established is based on the physical
location of the pen. Theref ore, t he pen must be
moved to the position assumed by the subroutine
before the subroutine is called. A l s o , t he pen
position cannot be moved more than 327. 67 inches
in either X direction f rom its physical location at
the t ime the origin was last established.
Scale values are given in inches per unit of the
using program. F o r example, t o indicate a scale
of 1/4 inch equal to 1 foot, t he scale value would
be O. 25. T o indicate a scale of 1 inch equal to
10 years, t he scale would be 0.1. Di f f e r e n t scale
values can be assigned to the X axis and the Y axis.
The pen is usually aligned by ret ic le adjustment
to some point on the chart paper. T h e scale s ubroutine
establishes the origin at any des ired point
relative to the physical location of the pen when the
subroutine is called. Thereaf t er, o r unt il the
origin is moved, a l l measurements are calculated
f rom this origin to prevent an accumulation of
errors which would res ult f rom meas uring f rom
point to point with calculated values that have been
rounded off or truncated.
The values inserted by this subroutine are
positive or negative as measured perpendic ularly
f rom each desired axis to the present location of
the pen.
CALL S C A L F ( X
s
, Y
Extended s precision:
, X
o
CA L L S C A L E ( X
, Y
s
o
, Y
X)
s
number s of inches per user's unit to be used along
the , X
i X axis.
0
s
, Y
a
o
r
)
e
a
l
c
Plotter Subroutines 3
o
n
s