Up to now, I've thought of zip files (a popular compression format on DOS machines, much as .sit files from StuffIt Deluxe are on the Mac) as kids from the other side of town - tolerated at best. I see a lot of these interlopers from bulletin boards, and I occasionally modem documents to someone who runs a DOS machine. Short of buying Aladdin's StuffIt Deluxe or the Macintosh version of PKWare (which I've seen advertised but never reviewed), it used to be awkward to create a zip file on a Mac. Unzipping wasn't a problem, because A.P. Maika's several incarnations of UnZip did that nicely. I have used MacZip to create zip files, but I found it awkward, and I couldn't make it work unless I placed both the new archive and the original file in the same folder. Tommy Brown's <email@example.com> ZipIt 1.1.1 goes a long way towards making the .ZIP compression protocols available in Mac shareware.
ZipIt's interface is (expressly) modeled after Compact Pro. It uses many of the same commands and has similar dialogs. The manual is comprehensive, and the author is attentive to bug reports. I've used the latest version without any snags on a Brainstorm accelerated Plus and on an LC III.
Is it on a par with StuffIt Lite and Compact Pro? Not on features, not yet. It doesn't do folders, for one thing. You can select a folder containing several tiers of sub-folders, and it will compress the files within them, but doesn't respect the folder boundaries. ZipIt works its way right through the folders, compressing every file into one archive, and it won't allow files with the same name in the same archive. The manual mentions this limitation as something a future version will cure. Even on the DOS side, PKZip and PKUnzip preserve a directory structure only on receiving specific commands to do so - not as a default, like Compact Pro and StuffIt Lite.
ZipIt lets you choose whether to strip linefeeds or save a file in MacBinary format. Although I didn't experience problems when transferring ZipIt archives between Mac and DOS, the manual reports some complaints about compatibility between the two platforms. It's not an instrument of sorcery; you still have to pay attention to formats - whether the TEXT file you compress has linefeeds, what the DOS word processor at the other end can handle, and so on. I had no trouble creating the archive on the Mac and copying it to a DOS-formatted disk.
If you can, before you push your archive into the modem, see if PKUnzip can read it under DOS. If you are dealing with a text file, you can test it further by seeing if typing "TYPE textfile.txt" (where "textfile.txt" is the name of your text document) at the C: prompt produces the text of the file on your screen. This will tell you how much work you have to do before you archive the file. And ZipIt, though it can strip linefeeds, can't add them. For that, you need something else - Add/Strip on the Mac, for example, or your word processor conversion capabilities.
[For those confused by the linefeed issue, the Mac uses a carriage return (CR) to end a line, where as DOS uses a carriage return and linefeed combination (CR/LF). Thus, when transferring text files to a Mac from a DOS machine, you may see little boxes in front of every line since the Mac sees the CR, ends the line, and then doesn't know what to display for the linefeed character that comes next. Hence the little boxes. In going the other direction, Mac to DOS, you want to add linefeeds so DOS knows where lines end. -Adam]
Here are some before and after sizes (taken from the Finder window) and timings on compression (using my analog wristwatch, counting from when the program started compressing until it said Done). I tested Compact Pro 1.33, StuffIt Lite 3.0.5, and ZipIt 1.1.1, all on an LC III with 8 MB RAM.
Test One = 3.9 MB TEXT only
Archive Size Time Compact Pro 965 K 2 min 33 sec StuffIt Lite 890 K 4 min 58 sec ZipIt 878 K 4 min 32 sec
Test Two = 198K PICT
Archive Size Time Compact Pro 68 K 15 sec StuffIt Lite 65 K 12 sec ZipIt 63 K 18 sec
Test Three = 1.4 MB Microsoft Word 5.1 document with 2 PICTs
Archive Size Time Compact Pro 420 K 60 sec StuffIt Lite 380 K 132 sec ZipIt 358 K 152 sec
As you can see, ZipIt was in the ballpark with Compact Pro and StuffIt Lite in each test, although it won't compete with them any time soon in the Macintosh world as a whole. ZipIt's primary purpose is to provide compatibility with DOS compression formats (one reason for not testing applications or other formats that wouldn't transfer), and it appears to do that admirably.
You can find ZipIt 1.1.1 on the Internet at <sumex-aim.stanford.edu> as: