Galaksija BASIC

Galaksija BASIC
Galaksija BASIC
Developer(s)	Microsoft, Voja Antonić
Initial release	1983; 42 years ago
Platform	Galaksija
Type	Microsoft BASIC

Galaksija BASIC was the BASIC interpreter of the Galaksija build-it-yourself home computer from Yugoslavia. While being partially based on code taken from TRS-80 Level 1 BASIC, which the creator believed to have been a Microsoft BASIC,^[1] the extensive modifications of Galaksija BASIC—such as to include rudimentary array support, video generation code (as the CPU itself did it in absence of dedicated video circuitry) and generally improvements to the programming language—is said to have left not much more than flow-control and floating point code remaining from the original.

The core implementation of the interpreter was fully contained in the 4 KiB ROM "A" or "1". The computer's original mainboard had a reserved slot for an extension ROM "B" or "2" that added more commands and features such as a built-in Zilog Z80 assembler.

ROM "A"/"1" symbols and keywords

The core implementation, in ROM "A" or "1", contained 3 special symbols and 32 keywords:

!: begins a comment (equivalent of standard BASIC REM command)
#: Equivalent of standard BASIC DATA statement
&: prefix for hex numbers
ARR$(n): Allocates an array of strings, like DIM, but can allocate only array with name A$
BYTE: serves as PEEK when used as a function (e.g. PRINT BYTE(11123)) and POKE when used as a command (e.g. BYTE 11123,123).
CALL n: Calls BASIC subroutine as GOSUB in most other BASICs (e.g. CALL 100+4*X)
CHR$(n): converts an ASCII numeric code into a corresponding character (string)
DOT x, y: draws (command) or inspects (function) a pixel at given coordinates (0<=x<=63, 0<=y<=47).
DOT *: displays the clock or time controlled by content of Y$ variable. Not in standard ROM
EDIT n: causes specified program line to be edited
ELSE: standard part of IF-ELSE construct (Galaksija did not use THEN)
EQ: compare alphanumeric values X$ and Y$
FOR: standard FOR loop
GOTO: standard GOTO command
HOME: equivalent of standard BASIC CLS command - clears the screen
HOME n: protects n characters from the top of the screen from being scrolled away
IF: standard part of IF-ELSE construct (Galaksija did not use THEN)
INPUT: user entry of variable
INT(n): a function that returns the greatest integer value equal to or lesser than n
KEY(n): test whether a particular keyboard key is pressed
LIST: lists the program. Optional numeric argument specifies the first line number to begin listing with.
MEM: returns memory consumption data (need details here)
NEW: clears the current BASIC program
NEW n: clears BASIC program and moves beginning of BASIC area
NEXT: standard terminator of FOR loop
OLD: loads a program from tape
OLD n: loads program to different address
PTR: Returns address of the variable
PRINT: Printing numeric or string expression.
RETURN: Return from BASIC subroutine
RND: function (takes no arguments) that returns a random number between 0 and 1.
RUN: runs (executes) BASIC program. Optional numeric argument specifies the line number to begin execution with.
SAVE: saves a program to tape. Optional two arguments specify memory range to be saved (need details here).
STEP: standard part of FOR loop
STOP: stops execution of BASIC program
TAKE: replacement for READ and RESTORE. If the parameter is variable name, acts as READ, if it is number, acts as RESTORE
UNDOT x, y: "undraws" (resets) at specified coordinates (see DOT)
UNDOT *: Stops the clock, not part of ROM
USR: Calls machine code subroutine
WORD: Double byte PEEK and POKE