690-693



     pressing RESET or changing GRAPHICS modes.
     See location 201 ($C9) about changing the TAB settings used
     when a PRINT statement encounters a comma.

690-693        2B2-2B5        LOGMAP
     Logical line start bit map. These locations map the beginning
     physical line number for each logical line on the screen (initially
     24, for GR.0). Each bit in the first three bytes shows the start of a
     logical line if the bit equals one (three bytes equals eight bits *
     three equals 24 lines on the screen). The map format is as follows:

     Bit     7     6     5     4     3     2     1     0     Byte
     ------------------------------------------------------------
     Line    0     1     2     3     4     5     6     7      690
             8     9    10    11    12    13    14    15      691
            16    17    18    19    20    21    22    23      692
            --    --    --    --    --    --    --    --      693

     The last byte is ignored. The map bits are all set to one when the
     text screen is OPENed or CLEARed, when a GRAPHICS com-
     mand is issued or RESET is pressed. The map is updated as
     logical lines are entered, edited, or deleted.

694            2B6            INVFLG
     Inverse character flag; zero is normal and the initialization value
     (i.e., normal ATASCII video codes have BIT 7 equals zero). You
     POKE INVFLG with 128 ($80) to get inverse characters (BIT 7
     equals one). This register is normally set by toggling the Atari
     logo key; however, it can be user-altered. The display handler
     XOR's the ATASCII codes with the value in INVFLG at all times.
     See location 702 ($2BE) below.

     INVFLG works to change the input, not the output. For example,
     if you have A$ = "HELLO", POKE 694, 128 will not change A$
     when you PRINT it to the screen. However, if you POKE 694, 128
     before an INPUT A$, the string will be entered as inverse.

695            2B7            FILFLG
     Right fill flag for the DRAW command. If the current operation is
     a DRAW, then this register reads zero. If it is non-zero, the
     operation is a FILL.

696            2B8            TMPROW
     Temporary register for row used by ROWCRS (location 84; $54).

697,698        2B9,2BA        TMPCOL
     Temporary register for column used by COLCRS (locations 85,
     86; $55, $56).

699            2BB            SCRFLG
     Scroll flag; set if a scroll occurs. It counts the number of physical