144,145



     increment. These two are allocated six bytes each in BCD format
     (12 bytes total). The 13th byte is the counter variable number with
     the MSB set; the 14th and 15th are the line number and the 16th is
     the line offset to the FOR statement.
     RUNSTK is also called ENDSTAR; it is used by BASIC to point to
     the end of the string/array space pointed to by STARR above.

144,145        90,91          MEMTOP
     Pointer to the top of BASIC memory, the end of the space the
     program takes up. There may still be space between this address
     and the display list, the size of which may be retrieved by the
     FRE(0) command (which actually subtracts the MEMTOP value
     that is at locations 741 and 742; $2E5, $2E6). Not to be confused
     with locations 741 and 742, which have the same name but are an
     OS variable. MEMTOP is also called TOPSTK; it points to the top
     of the stack space pointed to by RUNSTK above.

     When reserving memory using location 106 ($6A) and MEMTOP,
     here's a short error-trapping routine you can add:

     10   SIZE = (PEEK(106) - # of pages yo
        u are reserving) * 256
     20   IF SIZE < = PEEK(144) + PEEK(145
        ) * 256 THEN PRINT " PROGRAM TOO L
        ARGE": END

     Locations 146 to 202 ($92 to $CA) are reserved for use by the 8K
     BASIC ROM.
     Locations 176 to 207 ($B0 to $CF) are reserved by the Assembler
     Editor cartridge for the user's page zero use. The Assembler debug
     routine also reserves 30 bytes in page zero, scattered from location 164
     ($A4) to 255 ($FF), but they cannot be used outside the debug process.
     (See De Re Atari, Rev. 1, Appendix A for a list of these available
     bytes.)

186,187        BA,BB          STOPLN
     The line where a program was stopped either due to an error or
     the use of the BREAK key, or a STOP or a TRAP statement
     occurred. You can use PEEK (186) + PEEK (187) * 256 in a
     GOTO or GOSUB statement.

195            C3             ERRSAVE
     The number of the error code that caused the stop or the TRAP.
     You can use this location in a program in a line such as:

     10 IF PEEK(195) <> 144 THEN 100

201            C9             PTABW
     This location specifies the number of columns between TAB
     stops. The first tab will beat PEEK(201). The default is ten. This is