On 10/1/20 11:40 PM, Warner Losh via cctalk wrote: > On Fri, Oct 2, 2020, 12:05 AM Tom Hunter via cctalk <cctalk@classiccmp.org> > wrote: > >> I have never figured out why Bob Supnik defined the magnetic tape >> containers (TAP files) with the one byte padding for odd length records. >> This seems very odd (pun intended). :-) >> Even on a machine which couldn't write 32 bit numbers (the record lenght) >> on odd boundaries you could write the 32 bit number as 4 individual bytes. >> Does anyone know the reason?
On the .TAP files that I provide to customers, I ignore the 16-bit granularity and supply odd-length records as appropriate. My own take is that the original was intended for DEC 16/32 bit hardware. There are other systems that make it impossible to write an odd-length record. More interesting are the 36-bit systems writing 7 track tapes (e.g. Univac 1100), where a tape record has to be a multiple of 18 bits/3 "bytes" long. An ANSI label record, for example, is 81 "bytes". Similar situations exist for 9 track tapes written on nominally 6-bit systems. --Chuck
