AT&T 6300 Manual

Written by
Agora Resource, Inc.
Lexington,
MA
©1984, 1985 AT&T
©1983, 1984 By Microsoft®
All Rights Reserved
Printed
in USA
NOTICE
The information in this document is subject to change without
notice.
AT&T assumes no responsibility for any errors that may
appear in this document.

BASIC
Programmers
Guide
Contents
1Introduction
Introduction 1-2
Major Features 1-3
Syntax Conventions
1-4
Line Format
1-7
Character Set 1-9
Reserved Words
1-10
2Getting Started
Initialization Procedure
2-2
Modes of Operation 2-3
Keyboard
2-4
The GWBASIC Screen Editor 2-12
Using Your System as aCalculator 2-23
Entering aProgram
2-26
Listing aProgram 2-29
Saving aProgram
2-30
Loading aProgram
2-31
Executing aProgram 2-32
Program Interrupts 2-37
3Variable Types
Constants
3-2
Variables 3-7
Expressions and Operators
3-14

BASIC
Programmers
Guide
4Disk File Handling
Device Independent Input/Output 4-2
How MS-DOS Keeps Track of Your Files 4-3
File Specification 4-5
Commands for Program Files
4-18
Disk Data Files -Sequential
and Random Access 4-21
5Graphics
Selecting the Screen Attributes 5-2
Text Mode
5-4
Graphics Mode 5-7
6Asynchronous
Communications
Opening Communications Files
6-2
Communication I/O 6-3
Communication I/O Functions 6-4
7Command References
Introduction 7-2
Commands, Statements,
and Functions with
Examples 7-16

BASIC
Programmers
Guide
Appendices
A
B
c
D
Tables
Hexadecimal Conversion Tables
ASCII Codes
Extended Codes
Hexadecimal to Decimal Conversion Tables
Derived Functions
Advanced Features
Memory Allocation
Internal Representation
Calling Subroutines
Event Trapping
Conversion of Programs to GWBASIC
Introduction
String Dimensioning
MAT Functions
Multiple Assignments
Multiple Statements
PEEKs and POKEs
IF ... THEN ... [ELSE ...]
File I/O
Graphics
Sounding the Bell
Error Codes and Error Messages
Error Messages
Error Codes
Glossary
Index
Supplement: Display Enhancement Board
A-3
A-4
A-8
A-lO
A-12
B-2
B-4
B-6
B-22
C-2
C-3
C-6
C-7
C-8
C-9
C-I0
C-ll
C-12
C-13
D-2
D-4

1Introduction
• Introduction
• Major Features
• Syntax Conventions
• Line Format
• Character Set
• Reserved Words
1-1

Introduction
INTRODUCTION
dWBASIC is the most extensive
implementation of
BASIC available for
personal computers.
It meets the requirements
of
the ANSI standard for BASIC, and
supports many features rarely found in other
BASICs. It provides sophisticated string
handling, structured programming features,
and improved graphics.
GWBASIC gives you ease of use plus features
that make your personal computer perform at
its best.
UNIX is a trademark of AT&T Bell Laboratories.
Ms™·bOS is a trademark of Microsoft Corporation.
Microsoft® is aregistered
trademark of Microsoft Corporation.
1-2

Introduction
MAJOR FEATURES
Some of the special features of GWBASIC are:
•
UNIX™ style MS™-DOS interface for auser-
friendly
operating environment
•Re-directable standard input and output
•Device communication commands to initialize
and communicate with peripheral devices
•
Tree-structured disk directories
•
Improved Disk I/O facilities for large files
•
Advanced screen editing
• Enhanced Graphics commands
•User-defined Keyboard, Error, and Event
Trapping
•Precise error reporting with ERDEV and
ERDEV$
• Optional double precision transcendentals
•Precise control of memory allocation
•
CALL statements with parameter passing
•Chaining with common variables to programs
larger than the available memory
• Optional declaration of variable names
1-3

Introduction
{ }
[ ]
1-4
SYNTAX CONVENTIONS
•Uppercase letters and words, and the sym-
bols
listed below, should be typed in the
actual line exactly as shown.
(),;:=!#$-><
In the statement:
WRITE #filenum, list-of-expressions
# and the comma (,) after filenum should be
typed as shown.
•Lowercase letters and words represent
variable information (or parameters) that the
user must provide. In the statement:
KILL filespec
filespec should be replaced by aspecific
value-for example, "MYFILE".
• The symbols listed below are used to define the
syntax of aline, but should not be typed in the
actual line:
vertical
stroke indicates alternatives
braces indicate achoice
brackets indicate options
ellipsis indicates repetition
underscore joins parts of names in amultiple-
word parameter

Introduction
•Braces group related items (divided by a
vertical stroke),
such as alternatives.
{AlBiC}
indicates
that you must choose one of the
items enclosed within the braces.
AorBorC
• Brackets also group related items (divided by a
vertical stroke); however,
everything within the
brackets is optional and may be omitted.
[AlBiC]
indicates that you may choose one of the items
enclosed within the brackets or that you may
omit all of the items.
•
An ellipsis indicates that the preceding item or
group of items may be repeated more than once
in succession.
A
[,B] ...
indicates that A can be typed alone or can be
followed by
,B
once or more in succession.
1-5

Introduction
1-6
Note
is also permitted and has the same meaning
as
A[,B] ...
• The underscore character (_) can be used to
join names in amultiple-word parameter. For
example:
ENVIRONS (nth_parm)
• Characters which appear in a listing in bold
face represent characters entered through the
keyboard.

Introduction
LINE FORMAT
GWBASIC lines may contain amaximum of
255 characters ~nd have the following format:
[nnnnn]
statement [:statement]...['comment] CR
AGWBASIC
program line always begins
with aline number (an unsigned integer in
the
range 0 to 65,529), and ends with acarriage
return· (CR). A program line is stored in
memory as soon as you
enter CR.
AGWBASIC immediate line,
Le., aline that is
executed
as soon as you enter it, always begins
with a
l~~ter, as you have to omit the line
number in
this case.
More
than one GWBASIC statement may be
placed on aline, but each successive statement
must be separated froIl} the last by acolon.
At the end of aGWBASIC line (before CR)
you may e:q.ter acomment string preceded by a
single quotation
mark (').
Acomment string preceded either by the
keyword REM or by asingle quotation mark
may also be written just after the line number.
You
can extend alogjcalline over more than
one physical line by pressing CTRL-CR or by
continuing typing and letting the logical line
wrap around
to the ne~t physical line.
All GWBASIC lines shown
in this manual
end with CR unless specifically
stated
otherwise.
1-7

Introduction
1-8
Examples:
10 FOR K=1TO 20
is a GWBASIC program line.
100 GOSUB 1000 'branch to SUB1
is a GWBASIC program line with a comment
at the end.
1000'SUB1
is a GWBASIC program line which contains
only acomment.
PRINT AS
is a GWBASIC immediate line.
•
Every GWBASIC program line begins with
aline number. Line numbers indicate the
order in which the program lines are stored in
memory. Line
numbers are also used as
references in branching and editing.
For the EDIT, LIST, AUTO, and DELETE
commands, aperiod (.) may be used to
reference the current line.

Introduction
CHARACTER SET
GWBASIC recognizes upper and lower case
letters of the alphabet, the digits 0 through 9,
and the following special characters:
Blank
Equals sign or assignment symbol
+ Plus sign
-Minus sign
* Asterisk or multiplication symbol
Slash or division symbol
Up arrow or exponentiation symbol
Left parenthesis
) Right parenthesis
% Percent sign or integer type declaration
character
# Number (or pound) sign or double
precision
type declaration
$Dollar sign or string type declaration
character
Exclamation point or single precision
type declaration character
Left bracket (*)
Right bracket (*)
Comma
Period
or decimal point
Single quotation mark (apostrophe)
"Double
quotation mark (string delimiter)
Semicolon
Colon &
Ampersand
?Question mark (PRINT abbreviation)
< Less than
> Greater than
\ Backslash or integer division symbol
@ At sign
_Underscore (*)
IVertical line or pipe
{
Left brace
}
Right brace
.Grave accent
Tilde
(*) Since these symbols are not used as
operators in the language, they may be used to
define the syntax (see Syntax Conventions
above).
They should be typed in the actual
line only if they belong to a string constant.
1·9

Introduction
RESERVED WORDS
LSET
MERGE
MID$
MKDIR
MKD$
MKI$
MKS$
MOD
NAME
NEW
NEXT
NOT
OCT$
OFF
ON
OPEN
OPTION
OR
OUT
PAINT
PEEK
PLAY
PMAP
POINT
POKE
POS
PRESET
PRINT
PRINT#
PSET
PUT
RANDOMIZE
READ
REM
RENUM
RESET
RESTORE
RESUME
RETURN
RIGHT$
ltMDIR
RND
RSET
EQV
ERASE
ERDEV
ERDEV$
ERL
ERR
ERROR
EXP
FIELD
FILES
FN
FIX
FOR
FRE
GET
GOSUB
GOTO
HEX$
IF
IMP
INKEY$
INP
INPUT
INPUT#
INPUT$
INSTR
INT
IOCTL
IOCTL$
KEY
KILL
LEFT$
LEN
LET
LINE
LIST
LLIST
LOAD
LOC
LOCATE
LOF
LOG
LPOS
LPRINT
GWBASIC comprises a set of statements,
commands, function names, and operator
names which are treated as reserved words,
and which cannot be used as variable names.
The
total list of GWBASIC reserved words is
as follows:
ABS
AND.
ASC
ATN
AUTO
BEEP
BLOAD
BSAVE
CALL
CALLS
CHAIN
CHDIR
CHR$
CINT
CIRCLE
CLEAR
CLOSE
CLS
COLOR
COM
COMMON
CONT
COS
CSNG
CSRLIN
CVD
CVI
CVS
DATA
DATE$
DEF
DEFDBL
DEFINT
DEFSNG
DEFSTR
DELETE
DIM
DRAW
EDIT
ELSE
END
ENVIRON
ENVIRON$
EOF
1-10

RUN
STRING
USR
SAVE STRING$ VAL
SCREEN SWAP VARPTR
SGN SYSTEM VARPTR$
SHELL TAB
VIEW
SIN TAN WAIT
SOUND
THEN
WEND
SPACE$
TIMER WHILE
SPC TIME$ WIDTH
SQR
TO WINDOW
STEP TROFF WRITE
STICK
STOP TRON WRITE#
STR$ USING XOR
Introduction
1-11

II
I
IIIII
III
I
IIIII
IIIIIIII
IIIIIIIIIII

2 Getting Started
• Initialization Procedure
• Modes of Operation
• Keyboard
• The GWBASIC Screen Editor
• Using Your System as a
Calculator
• Entering a Program
• Listing a Program
• Saving a Program
• Loading a Program
• Executing a Program
• Program Interrupts
2-1

Getting Started
2-2
INITIALIZATION
PROCEDURE
To start GWBASIC, the MS-DOS operating
system must first be installed. When MS-DOS
has been installed and the system prompt:
A>
is displayed, enter the GWBASIC command:
GWBASIC
to load GWBASIC from the diskette inserted
in drive A into memory.
Upon loading, GWBASIC responds with a
screen similar to the one shown below.
GWBASIC 2.02
(C) Copyright Microsoft 1983, 1984
AT&T Personal Computer Release 1.1
Copyright (C) 1984, 1985 by AT&T, all
rights reserved
XXXXX Bytes Free
Ok
• Insert a diskette containing your G WBASIC
programs and execute a program, or
• enter G WBASIC program or immediate lines.
• To exit from GWBASIC and return to MS-
DOS, enter:
SYSTEM
This closes all data files before returning to
MS-DOS. Your GWBASIC program is no
longer in memory. MS-DOS remains resident.