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Programmer Reference Guide

Introducting Eris

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BASIC Language Vocabulary

Introduction

BASIC, which is an acronym for Beginners All-purpose Symbolic Instruction Code, was first created in 1964 as a simple language for students to learn to use computers. By the late 70s it became the de-facto standard for most home computers. As system memory and capailities expanded, BASIC evolved from a simple functional language to a more complex structured language offering commands for graphics and sound. Many platforms based their varient of BASIC around Microsoft BASIC, one of the earliest dialects of BASIC. Since the purpose of Eris is to represent a modern retro computer, it is also based around a BASIC interpreter.

Eris BASIC is an amalgomation of the best dialects of BASIC at the time. It adopts the string handling of Microsoft BASIC with the structured programming of BBC BASIC. It takes colour commands from the ZX Spectrum.

BASIC Operators

Operator	Description	Example
!	Indirection operator	!a=42 print !a
%	Binary constant	%101010
&	Hexadecimal constant	&2A
'	Same as REM	'My program
*	Multiplication	X*Y
+	Addition String concatination	X+Y A$+"extra!"
-	Subtraction	Y-X
.	Set address label	.myLabel
/	Division	X/Y
< = >	Relational operators	X>42
@	Returns i-expr	PRINT @fred
?	Same as PRINT	? "Hello"
AND	Binary AND operator	count AND &7
NOT	Unary logical NOT operator	IF NOT A THEN ?"A is not zero"
OR	Binary OR operator	X = X OR &0F
TRUE	Constant -1	A = TRUE
XOR	Binary XOR operator	X = X XOR &0E
MOD	Binary modulus operator	X = X MOD 4
FALSE	Constant 0	A = FALSE

BASIC Keywords

Command	Short Description	Function Type
abs()		Numeric
alloc()		Address
asc()		String
assert
blit
call
chr$()		String
clear
cls	Clear screen
code
cursor	Move text cursor
delete	Delete a file
dim	Dimension a variable
dir	Display directory of files
draw	Draw a sprite

Description of BASIC Keywords

Programming Graphics on the Eris

Graphics Overview

Programmable Characters

Bitmapped Graphics

Sprites

Programming Sound and Music on the Eris