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e6817382 BJ |
1 | .TH HT 4 |
2 | .SH NAME | |
3 | ht \- RH-11/TE-16 magtape interface | |
4 | .SH DESCRIPTION | |
5 | The files | |
6 | .I "mt0, ..., mt15" | |
7 | refer to the DEC RH/TM/TE-16 magtape. | |
8 | The files | |
9 | .I "mt0, ..., mt7" | |
10 | are 800 bpi, and | |
11 | .I "mt8, ..., mt15" | |
12 | are 1600bpi. | |
13 | The files | |
14 | .I "mt0, ..., mt3" | |
15 | and | |
16 | .I "mt8, ..., mt11" | |
17 | are rewound when closed; the others are not. | |
18 | When a file open for writing is closed, a double end-of-file is written. | |
19 | .PP | |
20 | A standard tape consists of a | |
21 | series of 512 byte records terminated by an | |
22 | end-of-file. | |
23 | To the extent possible, the system makes | |
24 | it possible, if inefficient, to treat | |
25 | the tape like any other file. | |
26 | Seeks have their usual meaning and it is possible | |
27 | to read or write a byte at a time. | |
28 | Writing in very small units is inadvisable, | |
29 | however, because it tends to create monstrous record | |
30 | gaps. | |
31 | .PP | |
32 | The | |
33 | .I mt | |
34 | files discussed above are useful | |
35 | when it is desired to access the tape in a way | |
36 | compatible with ordinary files. | |
37 | When foreign tapes are to be dealt with, and especially | |
38 | when long records are to be read or written, the | |
39 | `raw' interface is appropriate. | |
40 | The associated files may be named | |
41 | .I "rmt0, ..., rmt15," | |
42 | but the same minor-device considerations | |
43 | as for the regular files still apply. | |
44 | .PP | |
45 | Each | |
46 | .I read | |
47 | or | |
48 | .I write | |
49 | call reads or writes the next record on the tape. | |
50 | In the write case the record has the same length as the | |
51 | buffer given. | |
52 | During a read, the record size is passed | |
53 | back as the number of bytes read, provided it is no greater | |
54 | than the buffer size; | |
55 | if the record is long, an error is indicated. | |
56 | In raw tape I/O, the buffer must begin on a word boundary | |
57 | and the count must be even. | |
58 | Seeks are ignored. | |
59 | A zero count is returned when a tape mark is read; | |
60 | another read will fetch the first record of the | |
61 | next tape file. | |
62 | .SH FILES | |
63 | /dev/mt?, | |
64 | /dev/rmt? | |
65 | .SH "SEE ALSO" | |
66 | tp(1) | |
67 | .SH BUGS | |
68 | The magtape system is supposed to be able | |
69 | to take 64 drives. | |
70 | Such addressing has never been tried. | |
71 | These bugs will be fixed when | |
72 | we get more experience with this device. | |
73 | .PP | |
74 | The driver is limited to four transports. | |
75 | .PP | |
76 | If any non-data error is encountered, it refuses to do anything | |
77 | more until closed. | |
78 | In raw I/O, there should be a way | |
79 | to perform forward and backward record and file spacing and | |
80 | to write an EOF mark explicitly. |