Atari 400 User Manual

Introduction to Atari BASIC 47
BASIC Variables
So far, we have only discussed data constants. A constant can be
defined as a fixed val ue. The following are examples of string and
numeric constants.
"Jack Novet"
"375"
27.59
o
100000
A name can be used to express data as well as a constant.
Variables are used to express data as a name.
A variable can be
defined as a quantity that can assume anyone
of a group of values. Variables are represented by variable
names. These consist
of a letter followed optionally by additional
letters and/ or numbers. The value assumed by a variable is
subject to change, depending upon the program statement
being executed . For example , in the following,
100 LET A = 5.0
200 LET B = 7.0
300 LET A = A + B
the variable A
is initially assigned a value of 5.0and B is assigned a
value
of 7.0. In line 300 , the variable A is assigned a new value
equal
to the sum of variables A and B, which is 12.0. The previous
value of A is erased.
Note the use of the LETsta tement in the preceding example . The
LET statement is used to assign a value to a variable. Whenever a
LET statement is used in a program, the value of the variable on
the left side of the equation is to be replaced with the value
appearing
on the right.
The reserved
word , LET need not actually be included in a LET
statement. Both of the following statements have the same

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)