Atari 400 Basic Reference Manual

LEN
STR$
VAL
38 Strings
10 FOR I=0 TO 25
~'0 PR I HT CHfU( ASC( .. A
11
)+I ) ) CHF.:$( A: :;C( "a" )+
I)
30 t·~E>=:T I
Figure 7-2. ASC and CHR$ Program Example
Note: There can be only one STR$ and only one CHR$ in a logical comparison.
Format:
LEN (sexp)
Example:
100 PRINT LEN(A$)
This function returns the length in bytes of the designated string . This informa-
tion may then be printed or used later in a program. The length of a string
variable is simply the index for the character which is currently at the end of
the string . Strings have a length ofO until characters have been stored in them.
It is possible to store into the middle of the string by using sub sc ripting.
However, the beginning of the string will contain garbage unless something
was stored (using STO) there previously.
The following routine illustrates one use of the LEN function:
10 Dir-1 A!( 10 >
2~3 A:i=u AT A~~ In
3( 1 F'~~ I f -~T LEt·i< A$ >
Figure 7-3. LEN Function Example
The result ofrunning the above program would be 5.
Format:
Example:
STR$ (aexp)
A$= STR$(65)
This string from number function returns the string form of the number in
parentheses . The above example would return the actual number 65, but it
would be recognized by the computer as a str ing .
Note: There can only be one STR$ and only one CHR$ in a logical comparison.
F or exa mple , A= STR$(1) > STR$(2) is not valid and will not wor k cor:rectly.
Format:
VAL(sexp)
Example:
100 A = V AL(A$)
This function returns a number of the same value as the number stored as a
string. This is the opposite of a STR$ function. Usi ng this function , the computer
can perform arithm e ti c operations on strings as s ho w n in th e following e xam-
ple program:
10 DH1 8$(5)
20 B:f.: II 10(10(11!
30 E:=SG!~\ I..JAL( B$) )
40 PRHH
11
THE SQUAPE POOT OF II , ;8$ .; II IS II
jB
Figure 7-4. VAL Function Program

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)