[cctalk] Burroughs DCALGOL vs tapes [from dead computer language thread]

Yes, DCALGOL is still around and actively used. It is a superset of the standard Extended ALGOL, and originally exposed some special APIs and data types for talking to the Datacom Processor front-end. Those APIs are still used, although the "front end" is now TCP/IP. The language has since been extended with numerous other APIs for use primarily by system-programmer types. There is also a DMALGOL compiler primarily used internally with the DBMS, DMSII. All three ALGOL variants have been compiled from the same source code since sometime in the '70s. DCALGOL would have been no different than ALGOL for dealing with tapes, and I'm surprised you found it harder to do with the MCP than with OS/360 EXCP I/O. Depending on the block and tape label formats, you may have had to do your own deblocking, and possibly read the tape as unlabeled, but the MCP I/O Logical I/O subsystem was quite rich even in 1975. You had to understand how the file attribute settings worked when dealing with non-native tape formats, however -- I've seen that trip a lot of people up. As an alternative, a variant of Logical I/O called Direct I/O was available, which is user-mode asynchronous I/O that reads and writes raw blocks. It's basically a thin wrapper around the MCP's internal Physical I/O mechanism. I know this is water long over the dam, but I'd be interested in hearing what kinds of issues you encountered, and if possible, a reference to the DEC formats you were trying to read.