PiDP-8/I SoftwareCheck-in [7f8d8bcff5]
Not logged in

Many hyperlinks are disabled.
Use anonymous login to enable hyperlinks.

Overview
Comment:Moved the "Strings are of Words, Not of Bytes or Characters" section of the CC8 user manual up within the document to be after the "Character Set" section, where it fits better. (This wasn't really possible back when the latter section was part of the stdio section.)
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA3-256:7f8d8bcff5fa2d72a69530c63d003507417795e4ddc77d481aa21d14dde59a80
User & Date: tangent 2019-02-13 19:13:25
Context
2019-02-19
03:13
Cherrypicked [52aa88863c] onto trunk, primarily to ensure that those with recent trunk checkouts don't get unexpectedly sent to branch cc8-cleanups. This change is harmless to have in both places. check-in: 0c7432da84 user: tangent tags: trunk
01:23
Moved [f]printf() buffer down into the otherwise sparsely used zero page, and rearranged the constants previously declared there to make better use of the space available. This then opens another half-page of space for the stack. Updated docs to cover all of this. EDIT: This is the start of a new branch because this checkin breaks some things, and some of the subsequent checkins destabilize CC8. I'm moving it to a branch until all that's fixed. check-in: 1ea9133a37 user: tangent tags: cc8-libc-zp-reorg
2019-02-13
19:13
Moved the "Strings are of Words, Not of Bytes or Characters" section of the CC8 user manual up within the document to be after the "Character Set" section, where it fits better. (This wasn't really possible back when the latter section was part of the stdio section.) check-in: 7f8d8bcff5 user: tangent tags: trunk
19:12
Added more detail about file I/O limitations to the LIBC user documentation section of the CC8 manual. (What used to be the "stdio" section is now broken up into several sections at the same level.) check-in: 23f92ab553 user: tangent tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to doc/cc8-manual.md.

546
547
548
549
550
551
552






















553
554
555
556
557
558
559
...
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
implementation. Even if you are reading your files with some other code
which is capable of handling 8-bit data, there are further difficulties
such as a lack of functions taking an explicit length, like `fwrite()`,
which makes dealing with ASCII NUL difficult. You could write a NUL to
an output file with `fputc()`, but not with `fputs()`, since NUL
terminates the output string.
























### <a id="fiolim"></a>File I/O Limitations

Because LIBC’s stdio implementation is built atop the OS/8 FORTRAN II
library, it only allows one file to be open at a time for reading and
one for writing. OS/8’s underlying limit is 5 output files and 9 input
files, which appears to be an accommodation specifically for its FORTRAN
................................................................................
corrupted the OS’s resident parts — or restart the PDP-8.

(You can restart OS/8 by causing a jump to core memory location 07600.
Within the `pidp8i` environment, you can hit Ctrl-E, then say “`go
7600`”.  From the front panel, press the Stop key, toggle 7600 into the
switch register, press the Load Add key, then press the Start key.)


### <a id="wordstr"></a>Strings are of Words, Not of Bytes or Characters

In several places, the Standard says a conforming C library is supposed
to operate on “bytes” or “characters,” at least according to [our chosen
interpretation][cppr]. Except for the text I/O restrictions called out
[above](#cset), LIBC operates on strings of PDP-8 words, not on these
modern notions of fixed 8-bit bytes or the ever-nebulous “characters.”

Because you may be used to the idea that string and memory functions
like [`memcpy()`](#memcpy) and [`strcat()`](#strcat) will operate on
bytes, we’ve marked all of these cases with a reference back to this
section.

By the same token, most functions that operate on NUL-terminated string
buffers in a conforming C library implementation actually check for a
word equal to 0000₈ in this implementation. The key thing to understand
is that these routines are not carefully masking off the top 4 or 5 bits
to check *only* against a 7- or 8-bit NUL character.

This is another manifestation of [CC8’s typeless nature](#typeless).


### <a id="missing"></a>Missing Functions

The bulk of the Standard C Library is not provided, including some
functions you’d think would go along nicely with those we do provide,
such as `feof()` or `fseek()`.  Keep in mind that the library is
currently restricted to [a single 4&nbsp;kWord field](#memory), and we







>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>







 







<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<







546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
...
625
626
627
628
629
630
631






















632
633
634
635
636
637
638
implementation. Even if you are reading your files with some other code
which is capable of handling 8-bit data, there are further difficulties
such as a lack of functions taking an explicit length, like `fwrite()`,
which makes dealing with ASCII NUL difficult. You could write a NUL to
an output file with `fputc()`, but not with `fputs()`, since NUL
terminates the output string.


### <a id="wordstr"></a>Strings are of Words, Not of Bytes or Characters

In several places, the Standard says a conforming C library is supposed
to operate on “bytes” or “characters,” at least according to [our chosen
interpretation][cppr]. Except for the text I/O restrictions called out
[above](#cset), LIBC operates on strings of PDP-8 words, not on these
modern notions of fixed 8-bit bytes or the ever-nebulous “characters.”

Because you may be used to the idea that string and memory functions
like [`memcpy()`](#memcpy) and [`strcat()`](#strcat) will operate on
bytes, we’ve marked all of these cases with a reference back to this
section.

By the same token, most functions that operate on NUL-terminated string
buffers in a conforming C library implementation actually check for a
word equal to 0000₈ in this implementation. The key thing to understand
is that these routines are not carefully masking off the top 4 or 5 bits
to check *only* against a 7- or 8-bit NUL character.

This is another manifestation of [CC8’s typeless nature](#typeless).


### <a id="fiolim"></a>File I/O Limitations

Because LIBC’s stdio implementation is built atop the OS/8 FORTRAN II
library, it only allows one file to be open at a time for reading and
one for writing. OS/8’s underlying limit is 5 output files and 9 input
files, which appears to be an accommodation specifically for its FORTRAN
................................................................................
corrupted the OS’s resident parts — or restart the PDP-8.

(You can restart OS/8 by causing a jump to core memory location 07600.
Within the `pidp8i` environment, you can hit Ctrl-E, then say “`go
7600`”.  From the front panel, press the Stop key, toggle 7600 into the
switch register, press the Load Add key, then press the Start key.)
























### <a id="missing"></a>Missing Functions

The bulk of the Standard C Library is not provided, including some
functions you’d think would go along nicely with those we do provide,
such as `feof()` or `fseek()`.  Keep in mind that the library is
currently restricted to [a single 4&nbsp;kWord field](#memory), and we