A BASIC program is a series of lines containing instructions for the BASIC
  compiler.   A  BASIC  program  line can contain a line number, one or more
  statements, an optional comment field, and a line terminator.

  LINE is also a special immediate mode variable that  allows  the  user  to
  determine  what statement was executing if a program was interrupted.  For
  example, if a CTRL/C is typed when a program was executing line  100,  the
  immediate mode statement PRINT LINE would display 100.

1  –  Ampersand

  An ampersand (&), followed immediately by a carriage return, allows  you
  to continue a BASIC statement on the next line.

2  –  Backslash

  The  backslash  statement  separator  (\)  separates  statements  in   a
  multi-statement line.

3  –  Continuation

  BASIC statements can be continued to the next text line if they end with
  an ampersand (&) immediately followed by a line terminator.

4  –  Length

  A text line (numbered line or continuation line) can contain up  to  255
  characters.

5  –  Numbers

  Line numbers are optional; you can compile, link and run a BASIC program
  without specifying line numbers.

  BASIC line numbers are positive whole numbers in the range 1  to  32767,
  inclusive.   Numbers  outside  this  range, fractional line numbers, and
  line numbers with embedded spaces or tabs generate errors.  Line numbers
  with  percent  signs  are  flagged  as  a  declining  feature  when  the
  /FLAG=DECLINING qualifier is enabled.  Leading zeroes are ignored.

  If you have a line-numberless program  that  contains  multiple  program
  units,  the  point at which BASIC breaks each program unit is determined
  by the placement of the statement that terminates the program unit.  Any
  text  that  follows  the  program terminator becomes associated with the
  following program unit.  A program terminator can be any  END  statement
  such as an END PROGRAM statement followed by any valid expression.

6  –  Terminators

  A carriage return/line feed sequence (<RETURN>) ends a program line.