Atari 800 Basic Reference Manual

Upon execution, the screen displays THE SQUARE ROOT OF B$ IS 100.
It is not possible to use the VAL function with a string that does not start with a
number, or that cannot be interpreted by the computer as a number. It can,
however, intrepret floating point numbers; e.g.,VAL("1E9")would return the
number 1,000,000,000.
STRING Strings can be manipulated in a variety of ways. They can be split, concatenated,
MANIPULATIONS rearranged, and sorted. The following paragraphs describe the different
manipulations.
String Concatenation
Concatenation means putting two or more strings together to form one large
string. Each string to be included in a larger string is called a substring . Each
substring must be dimensioned (see DIM). In Atari BASIC, a substring can con-
tain up to 99 characters (including spaces). After concatenation, the substrings
can be stored in another string variable, printed, or used in later sections of the
program. Figure 7-5 is a sample program demonstrating string concatenation.
In this program, A$, B$, and C$ are concatenated and placed in A$.
10 D I t1 A$( 1m; ) , 8$( 100 ) .. C$( 1 (u) )
:::.'0 A$= II sr~: I ~-lGS ::.: suB:;rp I ~-iGS ARE o I ~:cu:;sE
[I II
30 E:$=
11
IN 'AT A~: I BA:::IC--A SELF- TEACHmG
GUIDE Ill
4~3 C$=~~---CHAPTE~: 9. II
50 A$( LEt-K A$ H 1 )=B$
6£1 A$( LHK A$ )+ 1 >=C$
70 F'k:HH A$
Figure 7·5. String Concatenation Example
String Splitting
The format of a subscript string variable is as follows:
svarname(aexp1[ ,aexp2])
The svarname is used to indicate the unsubscripted string variable name (with
$). aexp1 indicates the starting location oft he substring and aexp2 (if used) in-
dicates the ending location of the substring. If no aexp2 is specified, then the end
of the substring is the current end of the string. The starting location cannot be
greater than the current length of the string . The two example programs in
Figure 7-6 illustrate a split string with no end location indicated and a split
string with an ending location indicated.
10 DH1 ~:$( 5)
20 S$="A8CD#"
3e PRWT S$( 2)
40 END
Result is BCD.
(without ending location)
10 D m :::$.:: 2~::1 >
20 S$=
11
ATAPI 80(1 E:A:::IC
11
30 PR I t·H S$( 7 .. 9 >
40 END
Result is 800.
(with e nding loc ation )
Figure 7·6. Split String Examples
St ri ngs 39

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