On 25/04/2012 10:18 PM, Warp wrote:
> Orchid Win7 v1<voi### [at] devnull>  wrote:
>> In a similar was, AMOS BASIC has local variables, named functions and
>> procedures, separate compilation, and a whole chock-load of features. In
>> fact, so many features that it hardly counts as "BASIC" any more; it's
>> more like a brand new language with a superficial resemblance to BASIC...
>
>    If I recall correctly, the original BASIC, and the vast majority of
> clones for a pretty long time, didn't even have

C64 BASIC is the very first programming language I ever learned, when I 
was still only 9 years old. (I soon learned many other dialects.)

The language is interpreted, not compiled. "Files" are stored on tape, 
so random access is impossible, and splitting a program across several 
files would be a pointless endeavour.

There is no text editor. Instead you edit the program using line 
numbers. Type in a command and it executes immediately. (So the BASIC 
interpreter is also the "operating system" as such.) Type in a line 
number followed by a command, and that line is added to the program. 
Lines are kept in sorted order, so you can insert between lines 
(provided their numbers are not consecutive). For this reason, lines are 
invariably numbered in 10s. Enter a line number that already exists, and 
the existing line is replaced. Enter a line number with nothing 
following it, and the line is deleted. The LIST command shows you the 
program listing as it currently exists.

There are three types of variable. Normal variables hold signed 
integers. (I have no idea what their range is.) Variable names ending 
with "#" hold floating-point values. (Remember, no FPU, so SLOOOW. Also, 
64KB of RAM, so these eat memory like candy.) Variable names ending with 
"$" hold variable-length text strings. Typically a string cannot be more 
than 255 characters. Typically a variable name cannot be more than 30 
characters - which is fine. The entire screen is only 40 characters 
wide. (A few BASIC implementations allow up to 30 characters, BUT IGNORE 
ANYTHING BEYOND 8!)

All variables are global variables.

There are no subroutines. There is only GOTO and GOSUB/RETURN. This is 
an UNSTRUCTURED programming language, after all.

You can have multi-dimensional arrays. They all start at index 1. There 
are no user-defined data types.

Your flow control constructs are IF/THEN/ELSE, WHILE/LOOP, REPEAT/UNTIL, 
and FOR/NEXT. Some dialects allow compound statements on a single line 
using ":" as separator. Others demand that you use THEN GOTO if you want 
multiple statements.

Almost every dialect had a strange DATA construct. A DATA statement is 
followed by a comma-separated list of decimal numbers. The READ 
statement fetches the next code into the specified variable. The RESTORE 
command resets to the first DATA statement. If you want to write machine 
code, you invariably have to write a BASIC program such as

10 FOR X = 1 TO 13
20   READ D
30   POKE (23874+X), D
40 NEXT X
50 DATA 45,84,27,45,95,13,75,65,42,84,13,10,59

This uses the POKE command to copy the stuff in the DATA statements into 
a given location in RAM. (Notice how the DATA statements accept only 
decimal. In general, BASIC understands nothing else.) This is arguably 
the only reason that I know that the op-code for the 6510 "RTS" (return 
from subroutine) command is 96 decimal.

To my mind, any language more sophisticated than this is no longer 
"BASIC". It is now "a language based on BASIC".

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