Atari 800 User Manual

Advanced Atari BASIC 87
Home Cursor
The home position can be defined as the upper left- hand corner
of the vid eo display. The h ome cursor co ntrol sequence moves
the cursor to the po s ition a nd e ra ses all ex isting data on the
screen as well.
Home cursor is frequently us ed to position the c ur sor and erase
the screen in Atari BASI C. Hom e c ursor ca n either be
acco mpli sh ed by using the ASCII code for home c ursor , 125,
with the CHR$ function , or by using e ith er of the following
escape sequences:
ES CI CTRL- <
ESC / SHIFT-<
with the PRINT statements.
POSITION Statement
The POS ITION stateme nt can be used to place the cursor at any
l ocat ion on the screen. The POS ITION stateme nt is used with the
following co nfi gurat ion ,
POSITION col umn , row
where column is the number of the co lumn to be moved to, and
ro w is th e numb er of the row to be mov ed to .
In actuality, the POSITION stateme nt does not cause the cursor
to be mov ed. POSITION merely changes the values in the Atari's
me mor y where the curs or locatio n is stored . When data is
subsequent ly displayed on the sc reen, that data will be displayed
at these new display coordinates.
The display r ow number is stored in memory address 84, and the
co lumn numb er is displayed in address 85. The co nt e nt s of these
lo cat ion s ca n be exam in ed w ith the PEEK function. For example,
the following statemen ts,
PEEK (84)
PEEK (85)

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