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With edit 201, the I/O system has been redone to handle internal files.
There are some incompatibilites:
- When you are end of line, the character in INPUT^ is
now a blank, as required by the standard. Previously
you saw the actual end of line character. To see
the actual character, you must turn on an option.
If you open the file INPUT via the PROGRAM statement,
specify PROGRAM FOO(INPUT:#). The :# specifies the
option to see end of line. (It way be combined with
/ for interactive, e.g. PROGRAM FOO(INPUT:/#) )
If you open the file via a RESET, specify /E:
RESET(INPUT,'foo.bar','/e'). If you also want it
openned interactively, specify /e and /i:
RESET(INPUT,'foo.bar','/i/e'). The old method of
putting magic bits in magic arguments will still work,
but the string argument specifying switches is clearly
much better. (Probably magic characters after INPUT:
will also be replaced by a similar list of switches
in the future.) Other useful switches are:
/o - I will handle open errors myself (Pascal sets EOF)
/d - I will handle data transmission errors myself
/f - I will handle format errors in read myself
/u - turn all lower case into upper case
/b:xx - byte size xx used in the OPENF
- When you do not specify a file name at all, e.g.
RESET(INFILE), where INFILE was not listed in the
PROGRAM statement, the system used to use the Pascal
variable name for the file name, e.g. DSK:INFILE..
Such cases are now treated as "internal files". Pascal
GENSYM's a file name, and the file is deleted when you
exit from the lexical context in which the variable
was defined (i.e. exit from the block, even by non-local
GOTO, or DISPOSE of the record if the file is part of
- The default for BREAK and BREAKIN has been changed to OUTPUT
and INPUT. Previously the default was TTY. I am trying
to deemphasize the standard file TTY, since it is not
present in standard Pascal. Furthermore, BREAK(TTY) and
BREAKIN(TTY) are essentially no-ops, so this does seem an
The major addition is that files can now be used in any reasonable
context, i.e. as parts of arrays, records, etc. However FILE OF
FILE is still not implemented.
This version of Pascal should be completely upwards-compatible
with Jensen and Wirth, except for quantitative limitations
(nesting limits of blocks, maximum length of a routine, etc.).
Please report any cases where it is not.
I don't remember the edit number, but sometime about a year ago,
Tops-10 I/O was redone to make it more compatible with the Tops-20
version. The main improvement was to random access. It is now
possible to move to any byte in the file and read or write (assuming
you are in update mode). At the same time, I eliminated a lot
of obscure features that complicated the coding, and didn't give
you anything you couldn't get easily by Pascal code. The major
examples I can think of are the record primitives, GETVAR, PUTVAR,
GETREC, CURREC, etc. There is a module GETVAR.PAS that implements
the old variable record primitives in Pascal. The fixed record
stuff can be done yourself. I don't remember the name of the
functions now, but to get record N, just do SETPOS(F,N*RECSIZE(F)),
and to find out the current record number, do CURPOS(F) DIV RECSIZE(F).
Also, the dump mode stuff (DUMPI/DUMPO) and the direct user USETI
and USETO have gone away. In my opinion they were needed only
under the old system. My random access was so bad that you might
have wanted to do your own using these primitives. I think that
is no longer needed, and it complicates things needlessly to give
the user hooks into the low levels.