The first line was omitted from the MLX-format listing for this program in the August issue (p. 100). It should read as follows:
C000:AD 20 D0 8D 0A C6 A5 73 7D
Screen Machine II
When entering the program that accompanies Part 1 of this article in the July issue (p. 86), you'll encounter many lines for which the published "Automatic Proofreader" checksum will not match the one returned by the Proofreader even when the line is entered exactly as listed. The program in the July listing was generated by processing the commented listing from Part 2 of the article in the August issue (Program 1, p. 95) with the "REMover" program in that issue (Program 2, p. 99). REMover removes all comments, but in the case of comments at the end of program lines it leaves the space between the last BASIC statement and the apostrophe ('). This space affects the checksum calculated by our lister program, but cannot be typed when you enter the program (any spaces after the last character in a program line are ignored). Except for the Proofreader checksums, the July "Screen Machine II" program is correct as listed, so it should work if entered as listed without using the Proofreader. The checksums should all be correct in the commented (August) version.
Apple ProDOS Catalog Sorter
The article with this utility program in the July issue (p. 96) states that the program can be modified for a 40-column video display simply by changing the PR#3 in line 260 to PR#0. Actually, several other changes are also required if you wish to display the sorted catalog on a 40-column screen: The HTAB statements should be removed from lines 340 and 780. The PRINT L2$: in line 460 should be changed to PRINT LEFT$(L2$,80-41*(A$<>"P")): and the PRINT DA$(I): in line 740 should be changed to PRINT LEFT$(DA$(I),80-41*(A$<>"P")):.
Also, the author has provided the following enhancement (this is not a correction). As published, the program sorts programs strictly by name. However, it's often useful to have programs sorted by type as well as by name, especially for directories on a hard disk. If you would like to modify the program to add this feature, change the assignment of the variable SK$(E) in line 680 to SK$(E)=MID$(L4$,18,3)+MID$(L4$,2,15).
Converting IBM ML to BASIC DATA
The article for this program erroneously states that this program will work on the PCjr. Cartridge BASIC for the PCjr does not support the SHELL command. (SHELL is included in Cartridge BASIC, but control does not return to BASIC after the command has executed.) Reader Wayne E. Robinson suggests a novel solution for PCjr owners: The PCjr normally uses Cartridge BASIC rather than either of the PC versions provided on the DOS disk, but it's not impossible to use the disk versions which properly support SHELL. When you type either BASIC or BASICA at a DOS A> prompt, DOS checks for the presence of Cartridge BASIC and displays an error message if no cartridge is found. You can trick the computer and use the disk versions of BASIC simply by changing their names. For example, you can use the ML-to-DATA program by using DOS to rename BASICA.COM as BASICB.COM, then typing BASICB (instead of BASICA) to start Advanced Disk BASIC, which can be used to run the program as listed.