### 6.7 Bug-for-Bug Compatibility

Some other implementations of SCCS have bugs, too. Where we know about these and can work around them, we do this. Please note that these bugs only affect some other versions of SCCS - if they affected all versions, they’d be the correct behaviour of CSSC too!

- Some versions of SCCS had a Y2K-related problem where the tens digit in the year fields within the delta table of the SCCS file contains a colon (‘:’) rather than a digit. When reading files, CSSC correctly understands this to be a zero and issues a warning message. The fault is corrected if the SCCS file is being modified. See Year 2000 Issues.
- Some versions of the Data General implementation were changed to use four-digit years in the p-file instead of two-digit years, apparently as part of a Y2K-fix. While arguably this in fact might have been the right way to fix the problem, none of the other SCCS implementations went along with the idea. See Year 2000 Issues. If the file is being modified, the year is written back out as a two-digit field.
- Although it is unusual for SCCS files to have “^A m” lines after “^A c” lines, this does sometimes occur. CSSC accepts either order, but always emits the MR numbers before the comments for each delta.
- CSSC accepts “^A m” lines with no argument, although this is unusual. This may in fact not actually be a bug.
- Some versions of SCCS (allegedly some versions of the Sun Code Manager product) emit lines of the form “^AU 0” instead of “^A U”. CSSC accepts either but only produces the latter. Similar situations exist for lines of the form “^At 0” and “^A T 0”.