File formats, makes of computer and operating systems

These documents are written from the assumption that most people in the Medical School use PC compatible computers but people also use the Sun minicomputers and some use Apple computers. Some issues arise transferring files between these systems. The first concerns diskette formats, the other concerns the nitty gritty of file formats.

Diskette formats

Sun computers and their operating system "Unix" don't do much by the diskette route so transfers to and from Suns should be done using the facilities of the network. FTP (File Transfer Protocol) should be used for large files rather standard DOS or Windows™copying as it is less likely to fail or corrupt things (that's not very likely but better safe....). The Internet section of the Unit's Artemis program has a friendly FTP program and is on all school PCs connected to the network. An Apple FTP program is available from the Unit. As far as I know, FTP and network copying on a Macintosh connected to the Network is the only way to get things between the Suns and Macs.

Macs more recent than the xxxx series and running System 7 or a more recent Mac operating system can handle PC 3.5" format 1.44Mb diskettes: see the Apple documentation on how to do that. In my limited experience of Macs, writing and reading is transparent and just like using Mac diskettes, only formatting a diskette in PC format needs the manual. Earlier 800kb Apple format diskettes and the Macs which used these, PC 720kb 3.5" diskettes and both 360kb and 1.2Mb sizes of 5¼" diskettes cannot be exchanged with Macintoshes. (I believe there are commercial programs to get PCs to handle 800kb Macintosh 3.5" diskettes but don't think they are available locally.)

File formats

One thing is simple: if you are using recent recommended Microsoft programs they recognise and handle each other's slightly different file formats painlessly. One issue exchanging things between Macs and other machines is that Mac files have a "resource fork" telling the operating system various things about what they contain. This information is lost in most ways of transferring things between Macs and PCs. As far as I know, this is rarely fatal as the Apple rebuilds this next time such a file is used. It may need some information from you to rebuild exactly what you need though.

Equally simply, application file

formats on Sun machines are just radically different from Mac or PC equivalents. For statistics packages there are generally application specific export formats that can be used, together with network transfer of the files, to get things between Sun and Mac/PC versions of the same statistics package.

The only other simple issue concerns straightforward text files: in Macs and PCs these are in what is called "ASCII" format which uses two eight bit characters to mark the end of lines (a "line feed" instruction and a "carriage return" instruction). Unix files do not use the "carriage return" character so such files transferred from Sun to PC or Mac can be unreadable and files transferred the other way are sometimes unreadable or sometimes just double spaced. The remedy is simple: the dos2unix and unix2dos programs on the Suns will convert the files (use "man dos2unix" or "man unix2dos" on the Sun for more explanation).