This program is developed for use on Hewlett Packard work stations. Because of the large amount of data DAT-tapes were used for storage and transferring from the Macintosh to the work stations. The DAT-tape format of Macintosh- and Unix operating system is not compatible so that the original Macintosh storage format had to be deciphered. The program only works for data files smaller than 41Mbytes. When larger files, the Macintosh closes the storage file and opens a new one. For transferring larger quantities of data more tapes were used.
The storage format have three different control sequences: FORK, CONT and TAIL. The CONT and the FORK sequence are followed by a static number of control bytes. The first control sequence appearing is FORK. This indicates the start of the file. The TAIL sequence indicates the end of a file. Unfortunately the name of the file together with data for the icons etc. are stored in front of the FORK sequence. This is problematic because we have to scan back and forth on the DAT- tape. The maximum size between the control sequences is 32.000 bytes. To avoid scanning back and forth on the tape 40.000 bytes are kept in memory for each time new data are read from the tape.
After the FORK sequence is found and the filename is identified, the file is read until next control sequence. If this is an TAIL sequence, the file is closed and the search for next file or end-of-mark is done. The buffer is filled whenever it is necessary between each control sequence. If the data are corrupted, the program aborts when reaching the end-of-file without saying that the file processing is finished.