Tiny Basic Grammar...

 
program -> (NUM statement)* ;
 

statement
  -> "LET" var "=" expression
  -> "IF" expression ("<" | "=" | ">")
        expression "THEN" statement
  -> "GOTO" expression
  -> "GOSUB" expression
  -> "RETURN"
  -> "RUN"
  -> "END"
  -> "REM" CHR* ;
 
...