Systems Reference Library IBM 1130/1800 Plotter Subroutines

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Graphs, curves, chart s , et c . , c an be developed by programming the appropriate instructions to the plotter. Because of the relative slowness of the plotter, compared with the computer, t he plot t er system has a buffering scheme which holds plot t er instructions unt il they are executed. T h i s leaves the computer f ree to do ot her jobs while the actual plot t ing is being completed. SUBROUTINE FUNCTI ONS There are s ix primary functions of the plot t er subroutines described in this manual. • Sc ale: Ac c ept s and stores scaling inf ormat ion required by the grid, plot and character functions. • G r i d : Dr a ws a line wit h scaled grid marks. • P l o t : Mov es the pen f rom it s present position to a new position. I t can also rais e or lower the pen either before or after the t rav ers e movement. • P o i n t : Dr a ws a special point character at the present location of the pen, i f the pen is down. Subroutine SCALE GRID PLOT POINT CHARACTER ANNOTATION (WRITE) Up and down status o f pen on execution Co-ordinates of pen on execution Required Before After Before After not applicable (n. a) (n. a) (n. a) down ( , 4 (n. a) a ) (xi. a) up user specification down • Figure 2. P e n status changes effected by the subroutines. 2 up up present position (p. p) (origin is established) (n. a) (p.p) (P• P) (P. P) those given to CHARACTER The point characters available are +, x , A , 7 , and
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 <strong>Plotter</strong> <strong>Subroutines</strong> 3 o n s
Page 1 and 2: Systems Reference Library IBM 1130/
Page 3: I LLUSTRATI ONS CONTENTS INTRODUCTI
Page 8 and 9: Y number s of inches per user's uni
Page 10 and 11: This subroutine assumes the pen is
Page 12 and 13: 8 ASSEMBLER Standard precision (exc
Page 14 and 15: APPENDI X B. SUBROUTI NE USAGE 10 S
Page 16 and 17: VARIABLE ALLOCATIONS IA II 1.002E00
Page 18 and 19: JOB / / FOR **PLOTTER TEST 9 *NAME
Page 20 and 21: 16 Figure 7. Plotter Test 5 Drawing
Page 22: I NDEX Annotation subroutine 7 Call
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Systems Reference Library IBM 1130/1800 Plotter Subroutines

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