Graph ics Co mm an d Set
Graphics Data Descriptor (GDD)
The Graphics Data Descriptor is the last structured field in the DATA portion of
the Write Graphics Control command. This field specifies the parameters for the
graphics window in the graphics medium presentation space (GPS) and sets the
drawing default conditions. The graphics window limits define the range of
drawing order coordinate values that map to the graphics object area.
Without causing an error, the drawing orders can specify GPS coordinates in the
X
'8000' to X'7FFF' range. The specified GDD graphics window limits select the
part of the drawing order’s picture to consider for mapping to the output area.
The format of the GDD field is:
Length A6BB Data
Table 76. Graphics Data Descriptor
Byte Value Description Error Code
0-1 X'001C'-End of
GDD
Length of Graphics Data Descriptor (GDD) X'0202..05'
2-3 X'A6BB' Structured Field ID X'020B..05'
4
X'00'
Unit Base (Measurement Units)
Unit Base is 10 Inches
X'0205..05'
5 X'00' Reserved
6-7
X'3840'
X'0960'
Xg Units per Unit Base
14400 L-units per 10 inches
2400 L-units per 10 inches
X'0206..05'
8-9
X'3840'
X'0960'
Yg Units per Unit Base Yg = Xg
14400 L-units per 10 inches
2400 L-units per 10 inches
X'0206..05'
10-13 X'00000000' Reserved
14-15 X'8000'-X'7FFF' Xg Left Limit of Graphics Presentation Space
Window See “Notation Conventions” on page 27
16-17 X'8000'-X'7FFF' Xg Right Limit of Graphics Presentation Space
Window See “Notation Conventions” on page 27
18-19 X'8000'-X'7FFF' Yg Top Limit of Graphics Presentation Space
Window See “Notation Conventions” on page 27
20-21 X'8000'-X'7FFF' Yg Bottom Limit of Graphics Presentation Space
Window See “Notation Conventions” on page 27
22-27 X'000000000000' Reserved
28-End Initial graphics default. See “GDD Initial Graphics
Defaults Self-Describing Instructions” on page 91
Note: See “GDD Initial Graphics Defaults Self-Describing Instructions” on
page 91. Figure 18 shows the Graphics Data Descriptor control parameters
specifying the size of the graphics window.
Chapter 3. IPDS Commands Reference 87
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