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The pages on this site contain documentation for very old MS-DOS software,
purely for historical purposes.
If you're looking for up-to-date documentation, particularly for programming,
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out of date.
BACKSPACE
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─────BACKSPACE──────────────────────────────────────────────────────────────
Action
Positions a file at the beginning of the preceding record.
Syntax
BACKSPACE {unitspec |
([UNIT=]unitspec
[, ERR=errlabel]
[, IOSTAT=iocheck])}
If UNIT= is omitted, <unitspec> must be the first parameter. The
parameters can otherwise appear in any order.
Parameter Description
unitspec An integer expression specifying an external
unit.
errlabel The label of an executable statement in the same
program unit. An I/O error causes transfer of
control to the statement at <errlabel>. If
<errlabel> is omitted, the effect of an I/O error
is determined by the presence or absence of
<iocheck>.
iocheck An integer variable that returns zero if there
is no error, or the error number if an error
occurs.
Remarks
The BACKSPACE statement is not legal with a file that has been
opened with MODE='WRITE'.
The BACKSPACE statement backs up one record, except in the
following special cases:
Special Case Result
No preceding record The file position is not changed
Preceding record is The file is positioned before
end-of-file record the end-of-file record
File position is The file is positioned to the
in middle of record start of that record
Examples
BACKSPACE 5
BACKSPACE (5)
BACKSPACE lunit
BACKSPACE (UNIT = lunit, ERR = 30, IOSTAT = ios)
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