203-207



     the value between items separated in a PRINT statement by com-
     mas -- such as PRINT AS, LOOP, C(12) -- not by the TAB key
     spacing.
     The minimum number of spaces between TABS is three. If you
     POKE 201,2, it will be treated as four spaces, and POKE 201,1 is
     treated as three spaces. POKE 201,0 will cause the system to
     hang when it encounters a PRINT statement with commas. To
     change the TAB key settings, see TABMAP (locations 675 to 689;
     $2A3 - $2B1). PTABW is not reset to the default value by pressing
     RESET or changing GRAPHICS modes (unlike TABMAP).
     PTABW works in all GRAPHICS modes, not merely in text
     modes. The size of the spaces between items depends on the pixel
     size in the GRAPHICS mode in use. For example, in GR.0, each
     space is one character wide, while in GR.8 each space is one-half
     color clock (one dot) wide.

203-207        CB-CF          ....
     Unused by either the BASIC or the Assembler cartridges.

208-209        D0-D1          ....
     Unused by BASIC. The only time I have seen any of these unused
     locations in use is in COMPUTE! (March 1982 and October
     1981), when they were used for user sort routines, and in ANTIC
     (June 1982), where they were used as flags in a graphic
     demonstration. The bytes from 203 to 209 ($CB to $D1) are the
     only page zero bytes uncontestably left free by BASIC.

210-211        D2-D3          ....
     Reserved for BASIC or other cartridge use.

Locations 212 to 255 ($D4 to $FF) are reserved for the floating point
package use. The FP routines are in ROM, from locations 55296 to
57393 ($D800 to $E031). These page zero locations may be used if the
FP package is not called by the user's program. However, do not use
any of these locations for an interrupt routine, since such routines
might occur during an FP routine called by BASIC, causing the
system to crash.

Floating Point uses a six-byte precision. The first byte of the Binary
Coded Decimal (BCD) number is the exponent (where if BIT 7 equals
zero, then the number is positive; if one, then it is negative). The next
five bytes are the mantissa. If only that were all there was to it. The
BCD format is rather complex and is best explained in chapter eight of
De Re Atari.

212-217        D4-D9          FR0
     Floating point register zero; holds a six-byte internal form of the
     FP number. The value at locations 212 and 213 are used to return
     a two-byte hexadecimal value in the range of zero to 65536