ioccc/1990/dds

Best Language Tool

Diomidis Spinellis
Imperial College, University of London
Myrsinis 1
GR-145 62 Kifissia
Greece

To build:

make all

To run

./dds

NOTE: this entry uses gets() so you might get a warning when compiling and running this entry.

Judges' comments

Give the following lines as input:

OLD LANDER.BAS
RUN

Be sure not to run out of fuel!


Modern compilers could not compile this entry but Yusuke Endoh supplied a patch
which lets it compile. Thank you Yusuke!

Author's comments

This is the DDS-BASIC Interpreter (Version 1.00). 

Immediate commands:

RUN	LIST	NEW	OLD filename
BYE	SAVE filename

Program commands:

variable names a to z		variables initialized to 0 on RUN
FOR var = exp TO exp		NEXT variable
GOSUB exp			RETURN
GOTO exp			IF exp THEN exp
INPUT variable			PRINT string
PRINT exp			var = exp
REM any text			END

Expressions (ranked by precedence):

Bracketed expressions
number (leading 0 for octal, 0x for hex, else decimal), variable
Unary -
* / 
+ - 
= <> 
> < 
<= >=
(* and + are also used for boolean AND and boolean OR)
Boolean expressions evaluate to 0 for false and 1 for true

Editing:

- Line editor using line re-entry.
- A line number with nothing following it, deletes the line.

Input format:

- Free format positioning of tokens on the line.
- No space is allowed before the line number.
- Exactly one space is needed between the OLD or SAVE command and 
  the filename.
- ALL INPUT MUST BE UPPERCASE.

Limits:

Line numbers		1-10000
Line length		999 characters
FOR nesting		26
GOSUB			999 levels
Program			Dynamically allocated
Expressions		-32768 - 32767 for 16 bit machines, 
			-2147483648 - 2147483647 for 32 bit machines

Error checking / error reports:

No error checking is performed.
The message `core dumped' signifies a syntax or semantic error.

Hosting Environment:

ANSI C, traditional K&R C or OSF ANDF
ASCII or EBCIDIC character set
48K bytes memory

The Speed of DDS-BASIC Interpreter (Version 1.00). relative to
Microsoft Advanced BASIC 3.31 is Approximately 60%.

The code size could be further reduced by doing ugly things like
not declaring the return type of functions, not freeing memory,
#defining define, and joining lines.  In its present 1536 character
form the program is reasonably portable (it may fail to run in a
tagged object architecture) and nicely formatted (it fits in an
80*25 screen).

Copyright (c) 1990, Landon Curt Noll & Larry Bassel. All Rights Reserved. Permission for personal, educational or non-profit use is granted provided this this copyright and notice are included in its entirety and remains unaltered. All other uses must receive prior permission in writing from both Landon Curt Noll and Larry Bassel.