run1: fixed-block, with 'proper' reads of block-length
c:\testtape

Opening Tape Handle
stblk.mt_blkno=0
ST0: Status: 41030000 BOT ON-LINE
Setting length 512 records. rc=0
ST0: Status: 41030000 BOT ON-LINE
rewind... rc=0
ST0: Status: 41030000 BOT ON-LINE
write... rc=512, errno=0
ST0: Status: 01030000 ON-LINE
stblk.mt_blkno=1
backspace... rc=0
ST0: Status: 41030000 BOT ON-LINE
stblk.mt_blkno=0
read... rc=512, errno=0
AC23456789
ST0: Status: 01030000 ON-LINE
stblk.mt_blkno=1
write... rc=512, errno=0
ST0: Status: 01030000 ON-LINE
stblk.mt_blkno=2
backspace... rc=0
ST0: Status: 01030000 ON-LINE
stblk.mt_blkno=1
read... rc=512, errno=0
BD23456789
ST0: Status: 01030000 ON-LINE
stblk.mt_blkno=2
rewind... rc=0
ST0: Status: 41030000 BOT ON-LINE
Closing Tape Handle

run2: with first-read only reading 1 character:
c:\testtape read1

Opening Tape Handle
stblk.mt_blkno=0
ST0: Status: 41030000 BOT ON-LINE
Setting length 512 records. rc=0
ST0: Status: 41030000 BOT ON-LINE
rewind... rc=0
ST0: Status: 41030000 BOT ON-LINE
write... rc=512, errno=0
ST0: Status: 01030000 ON-LINE
stblk.mt_blkno=1
backspace... rc=0
ST0: Status: 41030000 BOT ON-LINE
stblk.mt_blkno=0
read1... rc=1, errno=0
A
ST0: Status: 01030000 ON-LINE
stblk.mt_blkno=1
write... rc=512, errno=0
ST0: Status: 01030000 ON-LINE
stblk.mt_blkno=2
backspace... rc=0
ST0: Status: 01030000 ON-LINE
stblk.mt_blkno=1
read... rc=-1, errno=28

ST0: Status: 01030000 ON-LINE
stblk.mt_blkno=2
rewind... rc=0
ST0: Status: 41030000 BOT ON-LINE
Closing Tape Handle
      9 [main] testtape 102 handle_exceptions: Exception: 
STATUS_ACCESS_VIOLATION
   6056 [main] testtape 102 open_stackdumpfile: Dumping stack trace to 
testtape.exe.stackdump