Atari 400 Hardware Manual

Mixing Graphics Modes, cont.
III. PROCEDURE TO PRINT AND PLOT IN MIXED MODES, cont.
2. cont.
c. If few characters will be printed, then each character's
internal value may be looked up in the Internal
Character Set Table (Table 9.6), in the new BASIC
Reference Manual. This value is then POKED into
CHRPOS.
d. If strings are to be output, and if the ATASCII values
of all the characters lie within one of the ranges
shown in the table below, then do the following:
1) Obtain the appropriate ATASCII value range for
the characters
2) Do the OPERATION the table indicates on the
ATASCII value of each character.
3) POKE this value into CHRPOS.
ATASCII
VALUE
RANGE
OPERATION
0-31 Value +
64
32-95 Value
-
32
96-127
NONE
128-159 Value
+
64
160-223 Value
-
32
224-255 NONE
Example: 1) assume we want to print the word "TEXT"
in the mode 2 area of example #1 using
the CHRPOS calculated previously.
2) these characters are in the ATASCII
VALUE RANGE of "32 - 95".
3) the OPERATION for this range is "Value-32",
so 32 must be subtracted from each
ATASCII value.
4) the program statements would now look
like this:
T$(1,4)
CHRPOS
"TEXT"
MEMST + 2385
FOR X = 1 TO LEN(T$)
POKE CHRPOS +X - 1, ASC[T$(X,X))
- 32
NEXT X
t
(OPERATION: value
5) the FOR/NEXT loop POKEs the first
character ofT$, ASC[T$(X,X))-32, into
CHRPOS + O.
6) the next iteration POKEs the next
character of T$ into the next CHRPOS,
and so on.
B -7-
t
32)

Atari 400 Specifications

General

Manufacturer	Atari
Model	400
Type	Home Computer
Release Year	1979
CPU	MOS Technology 6502
CPU Speed	1.79 MHz
ROM	10 KB
Operating System	Atari OS
Keyboard	Membrane keyboard
RAM	8 KB (expandable to 48 KB)
Graphics	ANTIC and GTIA chips
Sound	4 channels
Display	RF output for connection to TV
Storage	Optional cassette tape drive or floppy disk drive
Ports	Cartridge
Display Resolution	320x192 (16 colors)