673



     playfield size.

673            2A1            TMPLBT
     Temporary storage for the bit mask.

674            2A2            ESCFLG
     Escape flag. Normally zero, it is set to 128 ($80) if the ESC key is
     pressed (on detection of the ESC character; 27, $1B). It is reset to
     zero following the output of the next character. To display
     ATASCII control codes without the use of an ESC character, set
     location 766 ($2FE) to a non-zero value.

675-689        2A3-2B1        TABMAP
     Map of the TAB stop positions. There are 15 byte (120 bits) here,
     each bit corresponding to a column in a logical line. A one in any
     bit means the TAB is set; to clear all TABs simply POKE every
     location with zero. There are 120 TAB locations because there
     are three physical lines to one logical line in GRAPHICS mode
     zero, each consisting of 40 columns. Setting the TAB locations for
     one logical line means they will also be set for each subsequent
     logical line until changed. Each physical line in one logical line
     can have different TAB settings, however.

     To POKE TAB locations from BASIC, you must POKE in the
     number (i.e., set the bit) that corresponds to the location of the
     bit in the byte (there are five bytes in each line). For example:
     To set tabs at locations 5, 23, 27 and 32, first visualize the line as a
     string of zeros with a one at each desired tab setting:

               0000100000000000000000100010000100000000

     Then break it into groups of eight bits (one byte units). There are
     three bytes with ones (bits set), two with all zeros:

     00001000 =  8
     00000000 =  0
     00000010 =  2
     00100001 = 33
     00000000 =  0

     Converting these to decimal, we get the values listed at the right
     of each byte. These are the numbers you'd POKE into locations
     675 (the first byte) to 679 (the fifth byte on the line). On powerup
     or when you OPEN the display screen (S: or E:), each byte is
     given a value of one (i.e., 00000001) so that there are tab default
     tab stops at 7, 15, 23, etc., incrementing by eight to 119. Also,
     the leftmost screen edge is also a valid TAB stop (2, 42, and 82).
     In BASIC, these are set by the SET-TAB and CLR-TAB keys.
     TABMAP also works for the lines in the text display window in
     split-screen formats. TABMAP is reset to the default values on