My notes on PC Exchange (very much a draft, so corrections are invited):
Apple File Exchange allowed Mac users to read and write PC disks but the user interface was not particularly friendly. Unsurprisingly, third party companies developed software that allowed PC disks to be used directly from the Mac desktop, and Apple purchased the code for AccessPC from Insignia Solutions to build their own product, PC Exchange. Early versions of PC Exchange had fewer features than third party products which gave them room to be developed independently. PC Exchange requires System 7.0 or higher, so if you are a System 6 user, read the information about AccessPC and DOS Mounter (not here, I'm afraid). Third party alternatives also offer better support for other removable drives.
PC Exchange was launched in early 1992 to support MS-DOS format floppy disks (720KB or 1.4MB) in an FDHD SuperDrive or any format supported by three external floppy drives (DaynaFile, PLI and Kennect). Version 1.0.x of PC Exchange does not work with MS-DOS format removable drives (eg Syquest, Zip), the Apple 5.25" PC floppy drive or hard disks. The control panel associates MS-DOS filename extensions with popular Mac applications, and is configurable. This allows you to double-click on a file icon (eg a Lotus 1-2-3 spreadsheet) on an MS-DOS floppy and open it in your preferred Mac application (eg Excel or Wingz). Early versions of PC Exchange do not attempt to translate in any way -- the Mac application needs to have its own translators for the PC format. PC Exchange also modifies the behaviour of the Finder so that it can format floppy disks in HFS or DOS FAT format. Early versions of PC Exchange (1.0.x) have limited functionality but are reliable (ie do not lose data). You may wish to conduct your own experiments using a hacked control panel with System 6.
PC Exchange 2.0 was launched in June 1994. Version 2.0.x supports the formats listed below:
* Apple II ProDOS 3.5" floppy disks, SCSI removable drives and SCSI hard disks
* MS-DOS format 3.5" floppy disks and 5.25" floppy disks in third party drives
* MS-DOS format SCSI removable drives and SCSI hard disks
* MS-DOS and ProDOS format PCMCIA storage cards
* Virtual hard disk files created by PC emulators
The PC Exchange 2.0 press announcement included a glowing recommendation from the manufacturers of Mac Link Plus. From System 7.5 onwards, PC Exchange became part of the Mac OS and a limited set of Mac Link translators were included up to Mac OS 8.1. PC Exchange 2.1.x was released around the time of Mac OS 7.6.
Quality control was poor at Apple when PC Exchange 2.0 and 2.1 were written, and I have personally lost data from MS-DOS disks using System 7.5.x. PC Exchange 2.0.5 from System 7.5.3 is considered the most reliable version from this era.
Mac OS 8.1 included PC Exchange 2.2 which introduced a number of enhancements and bug fixes. PC Exchange 2.2 removes the limit of 1GB for removable PC media found in earlier versions and adds support for Windows 95 long filenames and the FAT32 format. Filenames containing non-English characters are also better supported. **check retro fitting I think NO
From Mac OS 8.5, PC Exchange was renamed File Exchange 3.0 and became PowerPC native. It is much more reliable in supporting large external hard disks and removable drives. PCMCIA and ATA drives are supported in addition to SCSI and floppy. File translation, which had previously been managed by the Mac OS Easy Open control panel, was integrated into File Exchange. Later versions of File Exchange are bug fixes and do not add new features.