Atari 800 Basic Reference Manual

XIO (X.)
SPECIAL FILL
APPLICATION
Format:
Example:
XIO 18, #aexp, aexp1, aexp2, filespec
100 XIO 18, #6, 0, 0,
"S:"
This special application ofthe XIO statement fills an area on the screen between
plotted points and lines with a non-zero color value. Dummy variables (0) are
used for aexp1 and aexp2.
The following steps illustrate the fill process:
1. PLOT bottom right corner (point 1).
2. DRA
WTO upper right corner (point 2). This outlines the right edge of the
area to be filled.
3. DRA WTO upper left corner (point 3).
4. POSITION
cursor at lower left corner (point 4).
5. POKE address 765 with the fill color data (1, 2, or 3).
6. This method is used to fill each horizontal line from top to bottom oft he spe-
cified area . The fill starts at the left and proceeds across the line to the right
until it reaches a pixel which contains non-zero data (will wraparound if
necessary). This means that fill cannot be used to change an area w hi ch h as
been filled in with a non-zero value , as the fill will stop. The fill command
will go into an infinite loop if a fill with zero (0) data is attempted on a line
which has no non-zero pixels . I:I;H!M or (ifjWI;I@§i can be used to stop the
fill if this happens .
The following program creates a shape and fills it with a data (color) of 3. Note
that the XIO command draws in the lines of the left and bottom of the figure.
10 GRAF'H I c:; 5+ 16
2'0 COLOF.' 3
30 PLOT 70; 45
40 D~:A~-H C! 50 .' W
:-0 [ t RA~~JT~J 3(t .. 10
60 F'0:3ITI0fi 10,45
70 F'OKE 765 .: 3.
8f1 ::-no 1::: , #6, o .. o., ":; ·"
9ff GOTO 90
Figure 9-4. Example "FILL" Program
Assigning Colors To Characters In Text Modes 1 and 2
This procedure describes the method of assigning colors to the Atari character
set. First, look up the character numb er ·in Table 9-6. Then, see Table 9-7 to get
the conversion of that numb er required to ass ign a co lor register to it.
Example: Assign SETCOLOR 0 to lower case " r" in mode 2
w hose color is determin ed by register 0.
1. In Table 9-6, find the column and number for " r" (114-column 4).
2.
Using Table 9-7, locate column 4. Conversion is the cha racter number minu s
32 (114- 32 = 82 ).
54 Graphic Modes and Commands

Atari 800 Specifications

General

Processor	MOS Technology 6502
Processor Speed	1.79 MHz
ROM	10 KB
Graphics	ANTIC and GTIA chips
Release Year	1979
Display Resolution	up to 320 x 192
Colors	128 colors
Sound	4 channels
Storage	Cartridge, cassette, floppy disk
Ports	Cartridge, serial, monitor
Operating System	Atari OS