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Annotation of 43BSDTahoe/new/help/src/f77/io_random, revision 1.1.1.1

1.1       root        1: .TI F77/IO_RANDOM "Sep. 15, 1984"
                      2: Random Access I/O
                      3: 
                      4: F77 allows files to be accessed by both sequential and direct (random)
                      5: access reads and writes.
                      6: For example, suppose you want
                      7: to use random access I/O on unit 10 with records that are 20 bytes
                      8: long.
                      9: Open unit 10 by:
                     10: 
                     11: .nf
                     12:        open(10, file='randfile', form='unformatted',
                     13:        .       access='direct', recl=20 )
                     14: .fi
                     15: 
                     16: Write to it by:
                     17: 
                     18: .nf
                     19:        real vec(5)
                     20:           ...
                     21:        write(10, rec=n) vec
                     22: .fi
                     23: 
                     24: and read from it by:
                     25: 
                     26:        read(10, rec=n) vec
                     27: 
                     28: where n contains the record number being read or written.
                     29: The f77 I/O library
                     30: keeps track of the highest record number written to the file.
                     31: Any time
                     32: a write specifies a higher record number, the file is extended.
                     33: If a
                     34: read specifies a higher record number, an end-of-file error results.
                     35: Records not explicitly written contain zeros.

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