A printing problem obliterated a character in line 1580 of the Atari version of this game from the October issue (Program 1, p. 40). The line should read as follows:
1580 ML = USR(ADR(MOVE$), 57344, CHSET, 1024)
All versions of this game program from the September issue (p. 30) are correct as listed, except for a minor problem in the Amiga version. The copyright message in the first line of Program 4 should begin with an apostrophe ('), which Amiga Basic accepts as a substitute for the REM statement.
Reader Joseph Meany has provided an enhancement to the Commodore version (Program 1) which allows the game to be played with a joystick in addition to the keyboard. If you are interested in this modification, add or change the following lines:
840 GET A$:J=PEEK(56320):IF(A$ = " " AND J = 127) THEN 840 842 J = -13 * (J = 111) - 145 * (J = 126)- 17 * (J = 125) - 157 * (J = 123)-29*(J = 119) 844 IF A$ = " " THEN A$ = CHR$(J) 846 FOR DE = 1 TO 100 : NEXT DE
With these changes, you can use a joystick in port 2 to move the card cursor. Press the fire button to select a card. You must still use the keyboard to enter other commands.
BASIC Batch Files With Atari DOS
The article with this handy utility from the August issue (p. 81) suggested that batch files could be used to load and run BASIC programs. However, reader Justin E. Wilder discovered a problem with this technique. A BASIC program started from a batch file will crash with an ERROR 133 message if it contains any INPUT statements. This occurs because the the IOCB channel value in location 180 is left set to 7, the batch-file channel. The solution is to add a POKE 180,0 command to the batch file to reset the system for the default channel (the screen editor). To work properly, the POKE must appear on the same line as the LOAD or RUN command, and on the last line of the batch file (once the POKE is executed, no more lines will be read from the disk). For example, the proper batch-file line to automatically load and run a BASIC program named GAME.BAS would be POKE 180,0:RUN "D:GAME.BAS"
This memory-resident screen color selection program from the September issue (p. 82) will not work on the IBM PCjr.