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Modifications Or Corrections To Previous Articles

Atari Canyon Runner

The problem with this game from the October issue (Program 4, page 68) is not just a few missing bytes, as it might appear. A defective version of the program which creates MLX format listings added extraneous numbers to the machine language data. Fortunately, the problem is relatively easy to fix, and if you saved your typing you haven't lost any work.

If you haven't typed in "Canyon Runner" yet, you should enter the data as shown in the October issue. After you enter line 9896, you can either use the MLX Save option (CTRL-S), or add the line 9902 shown below to move to the Save feature. After you have a complete copy of Canyon Runner as published, proceed with the correction process.

First, create a temporary modified version of MLX to remove invalid bytes from your Canyon Runner data. Do this by adding one of the following sets of lines to MLX:

• If you created a boot tape, add:

AJ	935	IF NOT READ THEN 940
GA	936	BUFFER$ (FIN - BEG + 103) = CHR$ (0) : BUFFER$ (277) = BUFFER$ (281) : BUFFER$ (529) = BUFFER$ (533) : BUFFER$ (781) = BUFFER$ (785)
LJ	937	BUFFER$ (1033) = BUFFER$ (1037) : BUFFER$ (1285) = BUFFER$ (1289) : BUFFER$ (1537) = BUFFER$ (1541)

• If you created a binary file on disk, add:

AF	825	IF NOT READ THEN 830
FL	826	BUFFER$ (FIN - BEG + 127) = CHR$ (0) : BUFFER$ (253) = BUFFER$ (257) : BUFFER$ (505) = BUFFER$ (509) : BUFFER$ (757) = BUFFER$ (761)
KF	827	BUFFER$ (1009) = BUFFER$ (1013) : BUFFER$ (1261) = BUFFER$ (1265) : BUFFER$ (1513) = BUFFER$ (1517)

• If you created a boot disk, add:

NH	1185	BUFFER$ (283) = BUFFER$ (287) : BUFFER$ (535) = BUFFER$ (539): BUFFER$ (787) = BUFFER$ (791)
OG	1186	BUFFER$ (1039) = BUFFER$ (1043) : BUFFER$ (1291) = BUFFER$ (1295) : BUFFER$ (1543) = BUFFER$ (1547)

These changes are only for fixing Canyon Runner; they are not corrections to MLX, and you should not incorporate them as permanent modifications to MLX. The only errors in Atari MLX as published in the October issue were in the article, which failed to mention that on the Atari the special MLX functions are obtained with the CTRL key instead of the SHIFT key. For example, press CTRL-S to save your typing, CTRL-L to reload, CTRL-N to switch to a new address, etc. Also, the instructions for using the LOAD command are only for the Commodore 64.

Next, run the modified MLX (use 8192 for the start and run/init addresses, and 9904 as the ending address). Use the Load option (CTRL-L) to reload your Canyon Runner data. Use the Display option (CTRL-D) to examine lines 9866–9896. The data which was previously at lines 9890 and 9896 should appear to have moved up to 9866–9872. If this is not the case, check your typing of the MLX modifications and repeat this step.

Finally, use the MLX New Address option (CTRL-N) to change the entry address to 9878, then add the following lines:

9878 : 114, 105, 102, 032, 116, 105, 212
9884 : 104, 101, 109, 097, 103, 121, 023
9890 : 116, 108, 117, 099, 105, 102, 041
9896 : 102, 105, 100, 000, 000, 000, 219
9902 : 000, 000, 000, 000, 000, 000, 174

After you enter line 9902, MLX will move to the Save option. For safety, don't overwrite your existing copy of the Canyon Runner data. Use a different tape or disk if you are creating a boot version, or a different filename if you are creating a binary file. The result should be a working copy of Canyon Runner.

VIC Horse Racing

To get the proper checksum for line 670 of this game from the October issue (page 84), add a hyphen between BETS and HORSE. This correction should not affect the operation of the game.

360	CKSUM = 0 : A$ = N$ + L$ (X) : FOR I = 1 TO LEN(A$ ) : CKSUM = CKSUM + ASC(MID$ (A$ , I))*I) AND 255 : NEXT : A$ = CHR$ (65 + CKSUM/16) + CHR$ (65 + (CKSUM AND 15)) + " "
620	IF INSTR(ARG$ ,".") = 0 THEN ARG$ = ARG$ + ".BAS"