[perl5.git] / pod / perlebcdic.pod

=encoding utf8

=head1 NAME

perlebcdic - Considerations for running Perl on EBCDIC platforms

=head1 DESCRIPTION

An exploration of some of the issues facing Perl programmers
on EBCDIC based computers.  We do not cover localization,
internationalization, or multi-byte character set issues other
than some discussion of UTF-8 and UTF-EBCDIC.

Portions that are still incomplete are marked with XXX.

Perl used to work on EBCDIC machines, but there are now areas of the code where
it doesn't.  If you want to use Perl on an EBCDIC machine, please let us know
by sending mail to perlbug@perl.org

=head1 COMMON CHARACTER CODE SETS

=head2 ASCII

The American Standard Code for Information Interchange (ASCII or US-ASCII) is a
set of
integers running from 0 to 127 (decimal) that imply character
interpretation by the display and other systems of computers.
The range 0..127 can be covered by setting the bits in a 7-bit binary
digit, hence the set is sometimes referred to as "7-bit ASCII".
ASCII was described by the American National Standards Institute
document ANSI X3.4-1986.  It was also described by ISO 646:1991
(with localization for currency symbols).  The full ASCII set is
given in the table below as the first 128 elements.  Languages that
can be written adequately with the characters in ASCII include
English, Hawaiian, Indonesian, Swahili and some Native American
languages.

There are many character sets that extend the range of integers
from 0..2**7-1 up to 2**8-1, or 8 bit bytes (octets if you prefer).
One common one is the ISO 8859-1 character set.

=head2 ISO 8859

The ISO 8859-$n are a collection of character code sets from the
International Organization for Standardization (ISO), each of which
adds characters to the ASCII set that are typically found in European
languages, many of which are based on the Roman, or Latin, alphabet.

=head2 Latin 1 (ISO 8859-1)

A particular 8-bit extension to ASCII that includes grave and acute
accented Latin characters.  Languages that can employ ISO 8859-1
include all the languages covered by ASCII as well as Afrikaans,
Albanian, Basque, Catalan, Danish, Faroese, Finnish, Norwegian,
Portuguese, Spanish, and Swedish.  Dutch is covered albeit without
the ij ligature.  French is covered too but without the oe ligature.
German can use ISO 8859-1 but must do so without German-style
quotation marks.  This set is based on Western European extensions
to ASCII and is commonly encountered in world wide web work.
In IBM character code set identification terminology ISO 8859-1 is
also known as CCSID 819 (or sometimes 0819 or even 00819).

=head2 EBCDIC

The Extended Binary Coded Decimal Interchange Code refers to a
large collection of single- and multi-byte coded character sets that are
different from ASCII or ISO 8859-1 and are all slightly different from each
other; they typically run on host computers.  The EBCDIC encodings derive from
8-bit byte extensions of Hollerith punched card encodings.  The layout on the
cards was such that high bits were set for the upper and lower case alphabet
characters [a-z] and [A-Z], but there were gaps within each Latin alphabet
range.

Some IBM EBCDIC character sets may be known by character code set
identification numbers (CCSID numbers) or code page numbers.

Perl can be compiled on platforms that run any of three commonly used EBCDIC
character sets, listed below.

=head2 The 13 variant characters

Among IBM EBCDIC character code sets there are 13 characters that
are often mapped to different integer values.  Those characters
are known as the 13 "variant" characters and are:

    \ [ ] { } ^ ~ ! # | $ @ `

When Perl is compiled for a platform, it looks at some of these characters to
guess which EBCDIC character set the platform uses, and adapts itself
accordingly to that platform.  If the platform uses a character set that is not
one of the three Perl knows about, Perl will either fail to compile, or
mistakenly and silently choose one of the three.
They are:

=head2 0037

Character code set ID 0037 is a mapping of the ASCII plus Latin-1
characters (i.e. ISO 8859-1) to an EBCDIC set.  0037 is used
in North American English locales on the OS/400 operating system
that runs on AS/400 computers.  CCSID 0037 differs from ISO 8859-1
in 237 places, in other words they agree on only 19 code point values.

=head2 1047

Character code set ID 1047 is also a mapping of the ASCII plus
Latin-1 characters (i.e. ISO 8859-1) to an EBCDIC set.  1047 is
used under Unix System Services for OS/390 or z/OS, and OpenEdition
for VM/ESA.  CCSID 1047 differs from CCSID 0037 in eight places.

=head2 POSIX-BC

The EBCDIC code page in use on Siemens' BS2000 system is distinct from
1047 and 0037.  It is identified below as the POSIX-BC set.

=head2 Unicode code points versus EBCDIC code points

In Unicode terminology a I<code point> is the number assigned to a
character: for example, in EBCDIC the character "A" is usually assigned
the number 193.  In Unicode the character "A" is assigned the number 65.
This causes a problem with the semantics of the pack/unpack "U", which
are supposed to pack Unicode code points to characters and back to numbers.
The problem is: which code points to use for code points less than 256?
(for 256 and over there's no problem: Unicode code points are used)
In EBCDIC, for the low 256 the EBCDIC code points are used.  This
means that the equivalences

    pack("U", ord($character)) eq $character
    unpack("U", $character) == ord $character

will hold.  (If Unicode code points were applied consistently over
all the possible code points, pack("U",ord("A")) would in EBCDIC
equal I<A with acute> or chr(101), and unpack("U", "A") would equal
65, or I<non-breaking space>, not 193, or ord "A".)

=head2 Remaining Perl Unicode problems in EBCDIC

=over 4

=item *

Many of the remaining problems seem to be related to case-insensitive matching

=item *

The extensions Unicode::Collate and Unicode::Normalized are not
supported under EBCDIC, likewise for the encoding pragma.

=back

=head2 Unicode and UTF

UTF stands for C<Unicode Transformation Format>.
UTF-8 is an encoding of Unicode into a sequence of 8-bit byte chunks, based on
ASCII and Latin-1.
The length of a sequence required to represent a Unicode code point
depends on the ordinal number of that code point,
with larger numbers requiring more bytes.
UTF-EBCDIC is like UTF-8, but based on EBCDIC.

You may see the term C<invariant> character or code point.
This simply means that the character has the same numeric
value when encoded as when not.
(Note that this is a very different concept from L</The 13 variant characters>
mentioned above.)
For example, the ordinal value of 'A' is 193 in most EBCDIC code pages,
and also is 193 when encoded in UTF-EBCDIC.
All variant code points occupy at least two bytes when encoded.
In UTF-8, the code points corresponding to the lowest 128
ordinal numbers (0 - 127: the ASCII characters) are invariant.
In UTF-EBCDIC, there are 160 invariant characters.
(If you care, the EBCDIC invariants are those characters
which have ASCII equivalents, plus those that correspond to
the C1 controls (80..9f on ASCII platforms).)

A string encoded in UTF-EBCDIC may be longer (but never shorter) than
one encoded in UTF-8.

=head2 Using Encode

Starting from Perl 5.8 you can use the standard new module Encode
to translate from EBCDIC to Latin-1 code points.
Encode knows about more EBCDIC character sets than Perl can currently
be compiled to run on.

   use Encode 'from_to';

   my %ebcdic = ( 176 => 'cp37', 95 => 'cp1047', 106 => 'posix-bc' );

   # $a is in EBCDIC code points
   from_to($a, $ebcdic{ord '^'}, 'latin1');
   # $a is ISO 8859-1 code points

and from Latin-1 code points to EBCDIC code points

   use Encode 'from_to';

   my %ebcdic = ( 176 => 'cp37', 95 => 'cp1047', 106 => 'posix-bc' );

   # $a is ISO 8859-1 code points
   from_to($a, 'latin1', $ebcdic{ord '^'});
   # $a is in EBCDIC code points

For doing I/O it is suggested that you use the autotranslating features
of PerlIO, see L<perluniintro>.

Since version 5.8 Perl uses the new PerlIO I/O library.  This enables
you to use different encodings per IO channel.  For example you may use

    use Encode;
    open($f, ">:encoding(ascii)", "test.ascii");
    print $f "Hello World!\n";
    open($f, ">:encoding(cp37)", "test.ebcdic");
    print $f "Hello World!\n";
    open($f, ">:encoding(latin1)", "test.latin1");
    print $f "Hello World!\n";
    open($f, ">:encoding(utf8)", "test.utf8");
    print $f "Hello World!\n";

to get four files containing "Hello World!\n" in ASCII, CP 0037 EBCDIC,
ISO 8859-1 (Latin-1) (in this example identical to ASCII since only ASCII
characters were printed), and
UTF-EBCDIC (in this example identical to normal EBCDIC since only characters
that don't differ between EBCDIC and UTF-EBCDIC were printed).  See the
documentation of Encode::PerlIO for details.

As the PerlIO layer uses raw IO (bytes) internally, all this totally
ignores things like the type of your filesystem (ASCII or EBCDIC).

=head1 SINGLE OCTET TABLES

The following tables list the ASCII and Latin 1 ordered sets including
the subsets: C0 controls (0..31), ASCII graphics (32..7e), delete (7f),
C1 controls (80..9f), and Latin-1 (a.k.a. ISO 8859-1) (a0..ff).  In the
table names of the Latin 1
extensions to ASCII have been labelled with character names roughly
corresponding to I<The Unicode Standard, Version 6.1> albeit with
substitutions such as s/LATIN// and s/VULGAR// in all cases, s/CAPITAL
LETTER// in some cases, and s/SMALL LETTER ([A-Z])/\l$1/ in some other
cases.  Controls are listed using their Unicode 6.1 abbreviatons.
The differences between the 0037 and 1047 sets are
flagged with **.  The differences between the 1047 and POSIX-BC sets
are flagged with ##.  All ord() numbers listed are decimal.  If you
would rather see this table listing octal values, then run the table
(that is, the pod source text of this document, since this recipe may not
work with a pod2_other_format translation) through:

=over 4

=item recipe 0

=back

    perl -ne 'if(/(.{29})(\d+)\s+(\d+)\s+(\d+)\s+(\d+)/)' \
     -e '{printf("%s%-5.03o%-5.03o%-5.03o%.03o\n",$1,$2,$3,$4,$5)}' \
     perlebcdic.pod

If you want to retain the UTF-x code points then in script form you
might want to write:

=over 4

=item recipe 1

=back

 open(FH,"<perlebcdic.pod") or die "Could not open perlebcdic.pod: $!";
 while (<FH>) {
     if (/(.{29})(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\.?(\d*)\s+(\d+)\.?(\d*)/)
     {
         if ($7 ne '' && $9 ne '') {
             printf(
                "%s%-5.03o%-5.03o%-5.03o%-5.03o%-3o.%-5o%-3o.%.03o\n",
                                            $1,$2,$3,$4,$5,$6,$7,$8,$9);
         }
         elsif ($7 ne '') {
             printf("%s%-5.03o%-5.03o%-5.03o%-5.03o%-3o.%-5o%.03o\n",
                                           $1,$2,$3,$4,$5,$6,$7,$8);
         }
         else {
             printf("%s%-5.03o%-5.03o%-5.03o%-5.03o%-5.03o%.03o\n",
                                                $1,$2,$3,$4,$5,$6,$8);
         }
     }
 }

If you would rather see this table listing hexadecimal values then
run the table through:

=over 4

=item recipe 2

=back

    perl -ne 'if(/(.{29})(\d+)\s+(\d+)\s+(\d+)\s+(\d+)/)' \
     -e '{printf("%s%-5.02X%-5.02X%-5.02X%.02X\n",$1,$2,$3,$4,$5)}' \
     perlebcdic.pod

Or, in order to retain the UTF-x code points in hexadecimal:

=over 4

=item recipe 3

=back

 open(FH,"<perlebcdic.pod") or die "Could not open perlebcdic.pod: $!";
 while (<FH>) {
     if (/(.{29})(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\.?(\d*)\s+(\d+)\.?(\d*)/)
     {
         if ($7 ne '' && $9 ne '') {
             printf(
                "%s%-5.02X%-5.02X%-5.02X%-5.02X%-2X.%-6.02X%02X.%02X\n",
                                           $1,$2,$3,$4,$5,$6,$7,$8,$9);
         }
         elsif ($7 ne '') {
             printf("%s%-5.02X%-5.02X%-5.02X%-5.02X%-2X.%-6.02X%02X\n",
                                              $1,$2,$3,$4,$5,$6,$7,$8);
         }
         else {
             printf("%s%-5.02X%-5.02X%-5.02X%-5.02X%-5.02X%02X\n",
                                                  $1,$2,$3,$4,$5,$6,$8);
         }
     }
 }


                          ISO
                         8859-1             POS-
                         CCSID  CCSID CCSID IX-
  chr                     0819   0037 1047  BC  UTF-8  UTF-EBCDIC
 ---------------------------------------------------------------------
 <NUL>                       0    0    0    0    0        0
 <SOH>                       1    1    1    1    1        1
 <STX>                       2    2    2    2    2        2
 <ETX>                       3    3    3    3    3        3
 <EOT>                       4    55   55   55   4        55
 <ENQ>                       5    45   45   45   5        45
 <ACK>                       6    46   46   46   6        46
 <BEL>                       7    47   47   47   7        47
 <BS>                        8    22   22   22   8        22
 <HT>                        9    5    5    5    9        5
 <LF>                        10   37   21   21   10       21  **
 <VT>                        11   11   11   11   11       11
 <FF>                        12   12   12   12   12       12
 <CR>                        13   13   13   13   13       13
 <SO>                        14   14   14   14   14       14
 <SI>                        15   15   15   15   15       15
 <DLE>                       16   16   16   16   16       16
 <DC1>                       17   17   17   17   17       17
 <DC2>                       18   18   18   18   18       18
 <DC3>                       19   19   19   19   19       19
 <DC4>                       20   60   60   60   20       60
 <NAK>                       21   61   61   61   21       61
 <SYN>                       22   50   50   50   22       50
 <ETB>                       23   38   38   38   23       38
 <CAN>                       24   24   24   24   24       24
 <EOM>                       25   25   25   25   25       25
 <SUB>                       26   63   63   63   26       63
 <ESC>                       27   39   39   39   27       39
 <FS>                        28   28   28   28   28       28
 <GS>                        29   29   29   29   29       29
 <RS>                        30   30   30   30   30       30
 <US>                        31   31   31   31   31       31
 <SPACE>                     32   64   64   64   32       64
 !                           33   90   90   90   33       90
 "                           34   127  127  127  34       127
 #                           35   123  123  123  35       123
 $                           36   91   91   91   36       91
 %                           37   108  108  108  37       108
 &                           38   80   80   80   38       80
 '                           39   125  125  125  39       125
 (                           40   77   77   77   40       77
 )                           41   93   93   93   41       93
 *                           42   92   92   92   42       92
 +                           43   78   78   78   43       78
 ,                           44   107  107  107  44       107
 -                           45   96   96   96   45       96
 .                           46   75   75   75   46       75
 /                           47   97   97   97   47       97
 0                           48   240  240  240  48       240
 1                           49   241  241  241  49       241
 2                           50   242  242  242  50       242
 3                           51   243  243  243  51       243
 4                           52   244  244  244  52       244
 5                           53   245  245  245  53       245
 6                           54   246  246  246  54       246
 7                           55   247  247  247  55       247
 8                           56   248  248  248  56       248
 9                           57   249  249  249  57       249
 :                           58   122  122  122  58       122
 ;                           59   94   94   94   59       94
 <                           60   76   76   76   60       76
 =                           61   126  126  126  61       126
 >                           62   110  110  110  62       110
 ?                           63   111  111  111  63       111
 @                           64   124  124  124  64       124
 A                           65   193  193  193  65       193
 B                           66   194  194  194  66       194
 C                           67   195  195  195  67       195
 D                           68   196  196  196  68       196
 E                           69   197  197  197  69       197
 F                           70   198  198  198  70       198
 G                           71   199  199  199  71       199
 H                           72   200  200  200  72       200
 I                           73   201  201  201  73       201
 J                           74   209  209  209  74       209
 K                           75   210  210  210  75       210
 L                           76   211  211  211  76       211
 M                           77   212  212  212  77       212
 N                           78   213  213  213  78       213
 O                           79   214  214  214  79       214
 P                           80   215  215  215  80       215
 Q                           81   216  216  216  81       216
 R                           82   217  217  217  82       217
 S                           83   226  226  226  83       226
 T                           84   227  227  227  84       227
 U                           85   228  228  228  85       228
 V                           86   229  229  229  86       229
 W                           87   230  230  230  87       230
 X                           88   231  231  231  88       231
 Y                           89   232  232  232  89       232
 Z                           90   233  233  233  90       233
 [                           91   186  173  187  91       173  ** ##
 \                           92   224  224  188  92       224  ##
 ]                           93   187  189  189  93       189  **
 ^                           94   176  95   106  94       95   ** ##
 _                           95   109  109  109  95       109
 `                           96   121  121  74   96       121  ##
 a                           97   129  129  129  97       129
 b                           98   130  130  130  98       130
 c                           99   131  131  131  99       131
 d                           100  132  132  132  100      132
 e                           101  133  133  133  101      133
 f                           102  134  134  134  102      134
 g                           103  135  135  135  103      135
 h                           104  136  136  136  104      136
 i                           105  137  137  137  105      137
 j                           106  145  145  145  106      145
 k                           107  146  146  146  107      146
 l                           108  147  147  147  108      147
 m                           109  148  148  148  109      148
 n                           110  149  149  149  110      149
 o                           111  150  150  150  111      150
 p                           112  151  151  151  112      151
 q                           113  152  152  152  113      152
 r                           114  153  153  153  114      153
 s                           115  162  162  162  115      162
 t                           116  163  163  163  116      163
 u                           117  164  164  164  117      164
 v                           118  165  165  165  118      165
 w                           119  166  166  166  119      166
 x                           120  167  167  167  120      167
 y                           121  168  168  168  121      168
 z                           122  169  169  169  122      169
 {                           123  192  192  251  123      192  ##
 |                           124  79   79   79   124      79
 }                           125  208  208  253  125      208  ##
 ~                           126  161  161  255  126      161  ##
 <DEL>                       127  7    7    7    127      7
 <PAD>                       128  32   32   32   194.128  32
 <HOP>                       129  33   33   33   194.129  33
 <BPH>                       130  34   34   34   194.130  34
 <NBH>                       131  35   35   35   194.131  35
 <IND>                       132  36   36   36   194.132  36
 <NEL>                       133  21   37   37   194.133  37   **
 <SSA>                       134  6    6    6    194.134  6
 <ESA>                       135  23   23   23   194.135  23
 <HTS>                       136  40   40   40   194.136  40
 <HTJ>                       137  41   41   41   194.137  41
 <VTS>                       138  42   42   42   194.138  42
 <PLD>                       139  43   43   43   194.139  43
 <PLU>                       140  44   44   44   194.140  44
 <RI>                        141  9    9    9    194.141  9
 <SS2>                       142  10   10   10   194.142  10
 <SS3>                       143  27   27   27   194.143  27
 <DCS>                       144  48   48   48   194.144  48
 <PU1>                       145  49   49   49   194.145  49
 <PU2>                       146  26   26   26   194.146  26
 <STS>                       147  51   51   51   194.147  51
 <CCH>                       148  52   52   52   194.148  52
 <MW>                        149  53   53   53   194.149  53
 <SPA>                       150  54   54   54   194.150  54
 <EPA>                       151  8    8    8    194.151  8
 <SOS>                       152  56   56   56   194.152  56
 <SGC>                       153  57   57   57   194.153  57
 <SCI>                       154  58   58   58   194.154  58
 <CSI>                       155  59   59   59   194.155  59
 <ST>                        156  4    4    4    194.156  4
 <OSC>                       157  20   20   20   194.157  20
 <PM>                        158  62   62   62   194.158  62
 <APC>                       159  255  255  95   194.159  255      ##
 <NON-BREAKING SPACE>        160  65   65   65   194.160  128.65
 <INVERTED "!" >             161  170  170  170  194.161  128.66
 <CENT SIGN>                 162  74   74   176  194.162  128.67   ##
 <POUND SIGN>                163  177  177  177  194.163  128.68
 <CURRENCY SIGN>             164  159  159  159  194.164  128.69
 <YEN SIGN>                  165  178  178  178  194.165  128.70
 <BROKEN BAR>                166  106  106  208  194.166  128.71   ##
 <SECTION SIGN>              167  181  181  181  194.167  128.72
 <DIAERESIS>                 168  189  187  121  194.168  128.73   ** ##
 <COPYRIGHT SIGN>            169  180  180  180  194.169  128.74
 <FEMININE ORDINAL>          170  154  154  154  194.170  128.81
 <LEFT POINTING GUILLEMET>   171  138  138  138  194.171  128.82
 <NOT SIGN>                  172  95   176  186  194.172  128.83   ** ##
 <SOFT HYPHEN>               173  202  202  202  194.173  128.84
 <REGISTERED TRADE MARK>     174  175  175  175  194.174  128.85
 <MACRON>                    175  188  188  161  194.175  128.86   ##
 <DEGREE SIGN>               176  144  144  144  194.176  128.87
 <PLUS-OR-MINUS SIGN>        177  143  143  143  194.177  128.88
 <SUPERSCRIPT TWO>           178  234  234  234  194.178  128.89
 <SUPERSCRIPT THREE>         179  250  250  250  194.179  128.98
 <ACUTE ACCENT>              180  190  190  190  194.180  128.99
 <MICRO SIGN>                181  160  160  160  194.181  128.100
 <PARAGRAPH SIGN>            182  182  182  182  194.182  128.101
 <MIDDLE DOT>                183  179  179  179  194.183  128.102
 <CEDILLA>                   184  157  157  157  194.184  128.103
 <SUPERSCRIPT ONE>           185  218  218  218  194.185  128.104
 <MASC. ORDINAL INDICATOR>   186  155  155  155  194.186  128.105
 <RIGHT POINTING GUILLEMET>  187  139  139  139  194.187  128.106
 <FRACTION ONE QUARTER>      188  183  183  183  194.188  128.112
 <FRACTION ONE HALF>         189  184  184  184  194.189  128.113
 <FRACTION THREE QUARTERS>   190  185  185  185  194.190  128.114
 <INVERTED QUESTION MARK>    191  171  171  171  194.191  128.115
 <A WITH GRAVE>              192  100  100  100  195.128  138.65
 <A WITH ACUTE>              193  101  101  101  195.129  138.66
 <A WITH CIRCUMFLEX>         194  98   98   98   195.130  138.67
 <A WITH TILDE>              195  102  102  102  195.131  138.68
 <A WITH DIAERESIS>          196  99   99   99   195.132  138.69
 <A WITH RING ABOVE>         197  103  103  103  195.133  138.70
 <CAPITAL LIGATURE AE>       198  158  158  158  195.134  138.71
 <C WITH CEDILLA>            199  104  104  104  195.135  138.72
 <E WITH GRAVE>              200  116  116  116  195.136  138.73
 <E WITH ACUTE>              201  113  113  113  195.137  138.74
 <E WITH CIRCUMFLEX>         202  114  114  114  195.138  138.81
 <E WITH DIAERESIS>          203  115  115  115  195.139  138.82
 <I WITH GRAVE>              204  120  120  120  195.140  138.83
 <I WITH ACUTE>              205  117  117  117  195.141  138.84
 <I WITH CIRCUMFLEX>         206  118  118  118  195.142  138.85
 <I WITH DIAERESIS>          207  119  119  119  195.143  138.86
 <CAPITAL LETTER ETH>        208  172  172  172  195.144  138.87
 <N WITH TILDE>              209  105  105  105  195.145  138.88
 <O WITH GRAVE>              210  237  237  237  195.146  138.89
 <O WITH ACUTE>              211  238  238  238  195.147  138.98
 <O WITH CIRCUMFLEX>         212  235  235  235  195.148  138.99
 <O WITH TILDE>              213  239  239  239  195.149  138.100
 <O WITH DIAERESIS>          214  236  236  236  195.150  138.101
 <MULTIPLICATION SIGN>       215  191  191  191  195.151  138.102
 <O WITH STROKE>             216  128  128  128  195.152  138.103
 <U WITH GRAVE>              217  253  253  224  195.153  138.104  ##
 <U WITH ACUTE>              218  254  254  254  195.154  138.105
 <U WITH CIRCUMFLEX>         219  251  251  221  195.155  138.106  ##
 <U WITH DIAERESIS>          220  252  252  252  195.156  138.112
 <Y WITH ACUTE>              221  173  186  173  195.157  138.113  ** ##
 <CAPITAL LETTER THORN>      222  174  174  174  195.158  138.114
 <SMALL LETTER SHARP S>      223  89   89   89   195.159  138.115
 <a WITH GRAVE>              224  68   68   68   195.160  139.65
 <a WITH ACUTE>              225  69   69   69   195.161  139.66
 <a WITH CIRCUMFLEX>         226  66   66   66   195.162  139.67
 <a WITH TILDE>              227  70   70   70   195.163  139.68
 <a WITH DIAERESIS>          228  67   67   67   195.164  139.69
 <a WITH RING ABOVE>         229  71   71   71   195.165  139.70
 <SMALL LIGATURE ae>         230  156  156  156  195.166  139.71
 <c WITH CEDILLA>            231  72   72   72   195.167  139.72
 <e WITH GRAVE>              232  84   84   84   195.168  139.73
 <e WITH ACUTE>              233  81   81   81   195.169  139.74
 <e WITH CIRCUMFLEX>         234  82   82   82   195.170  139.81
 <e WITH DIAERESIS>          235  83   83   83   195.171  139.82
 <i WITH GRAVE>              236  88   88   88   195.172  139.83
 <i WITH ACUTE>              237  85   85   85   195.173  139.84
 <i WITH CIRCUMFLEX>         238  86   86   86   195.174  139.85
 <i WITH DIAERESIS>          239  87   87   87   195.175  139.86
 <SMALL LETTER eth>          240  140  140  140  195.176  139.87
 <n WITH TILDE>              241  73   73   73   195.177  139.88
 <o WITH GRAVE>              242  205  205  205  195.178  139.89
 <o WITH ACUTE>              243  206  206  206  195.179  139.98
 <o WITH CIRCUMFLEX>         244  203  203  203  195.180  139.99
 <o WITH TILDE>              245  207  207  207  195.181  139.100
 <o WITH DIAERESIS>          246  204  204  204  195.182  139.101
 <DIVISION SIGN>             247  225  225  225  195.183  139.102
 <o WITH STROKE>             248  112  112  112  195.184  139.103
 <u WITH GRAVE>              249  221  221  192  195.185  139.104  ##
 <u WITH ACUTE>              250  222  222  222  195.186  139.105
 <u WITH CIRCUMFLEX>         251  219  219  219  195.187  139.106
 <u WITH DIAERESIS>          252  220  220  220  195.188  139.112
 <y WITH ACUTE>              253  141  141  141  195.189  139.113
 <SMALL LETTER thorn>        254  142  142  142  195.190  139.114
 <y WITH DIAERESIS>          255  223  223  223  195.191  139.115

If you would rather see the above table in CCSID 0037 order rather than
ASCII + Latin-1 order then run the table through:

=over 4

=item recipe 4

=back

 perl \
    -ne 'if(/.{29}\d{1,3}\s{2,4}\d{1,3}\s{2,4}\d{1,3}\s{2,4}\d{1,3}/)'\
     -e '{push(@l,$_)}' \
     -e 'END{print map{$_->[0]}' \
     -e '          sort{$a->[1] <=> $b->[1]}' \
     -e '          map{[$_,substr($_,34,3)]}@l;}' perlebcdic.pod

If you would rather see it in CCSID 1047 order then change the number
34 in the last line to 39, like this:

=over 4

=item recipe 5

=back

 perl \
    -ne 'if(/.{29}\d{1,3}\s{2,4}\d{1,3}\s{2,4}\d{1,3}\s{2,4}\d{1,3}/)'\
    -e '{push(@l,$_)}' \
    -e 'END{print map{$_->[0]}' \
    -e '          sort{$a->[1] <=> $b->[1]}' \
    -e '          map{[$_,substr($_,39,3)]}@l;}' perlebcdic.pod

If you would rather see it in POSIX-BC order then change the number
39 in the last line to 44, like this:

=over 4

=item recipe 6

=back

 perl \
    -ne 'if(/.{29}\d{1,3}\s{2,4}\d{1,3}\s{2,4}\d{1,3}\s{2,4}\d{1,3}/)'\
     -e '{push(@l,$_)}' \
     -e 'END{print map{$_->[0]}' \
     -e '          sort{$a->[1] <=> $b->[1]}' \
     -e '          map{[$_,substr($_,44,3)]}@l;}' perlebcdic.pod


=head1 IDENTIFYING CHARACTER CODE SETS

To determine the character set you are running under from perl one
could use the return value of ord() or chr() to test one or more
character values.  For example:

    $is_ascii  = "A" eq chr(65);
    $is_ebcdic = "A" eq chr(193);

Also, "\t" is a C<HORIZONTAL TABULATION> character so that:

    $is_ascii  = ord("\t") == 9;
    $is_ebcdic = ord("\t") == 5;

To distinguish EBCDIC code pages try looking at one or more of
the characters that differ between them.  For example:

    $is_ebcdic_37   = "\n" eq chr(37);
    $is_ebcdic_1047 = "\n" eq chr(21);

Or better still choose a character that is uniquely encoded in any
of the code sets, e.g.:

    $is_ascii           = ord('[') == 91;
    $is_ebcdic_37       = ord('[') == 186;
    $is_ebcdic_1047     = ord('[') == 173;
    $is_ebcdic_POSIX_BC = ord('[') == 187;

However, it would be unwise to write tests such as:

    $is_ascii = "\r" ne chr(13);  #  WRONG
    $is_ascii = "\n" ne chr(10);  #  ILL ADVISED

Obviously the first of these will fail to distinguish most ASCII platforms
from either a CCSID 0037, a 1047, or a POSIX-BC EBCDIC platform since "\r" eq
chr(13) under all of those coded character sets.  But note too that
because "\n" is chr(13) and "\r" is chr(10) on the Macintosh (which is an
ASCII platform) the second C<$is_ascii> test will lead to trouble there.

To determine whether or not perl was built under an EBCDIC
code page you can use the Config module like so:

    use Config;
    $is_ebcdic = $Config{'ebcdic'} eq 'define';

=head1 CONVERSIONS

=head2 tr///

In order to convert a string of characters from one character set to
another a simple list of numbers, such as in the right columns in the
above table, along with perl's tr/// operator is all that is needed.
The data in the table are in ASCII/Latin1 order, hence the EBCDIC columns
provide easy-to-use ASCII/Latin1 to EBCDIC operations that are also easily
reversed.

For example, to convert ASCII/Latin1 to code page 037 take the output of the
second numbers column from the output of recipe 2 (modified to add '\'
characters), and use it in tr/// like so:

    $cp_037 =
    '\x00\x01\x02\x03\x37\x2D\x2E\x2F\x16\x05\x25\x0B\x0C\x0D\x0E\x0F' .
    '\x10\x11\x12\x13\x3C\x3D\x32\x26\x18\x19\x3F\x27\x1C\x1D\x1E\x1F' .
    '\x40\x5A\x7F\x7B\x5B\x6C\x50\x7D\x4D\x5D\x5C\x4E\x6B\x60\x4B\x61' .
    '\xF0\xF1\xF2\xF3\xF4\xF5\xF6\xF7\xF8\xF9\x7A\x5E\x4C\x7E\x6E\x6F' .
    '\x7C\xC1\xC2\xC3\xC4\xC5\xC6\xC7\xC8\xC9\xD1\xD2\xD3\xD4\xD5\xD6' .
    '\xD7\xD8\xD9\xE2\xE3\xE4\xE5\xE6\xE7\xE8\xE9\xBA\xE0\xBB\xB0\x6D' .
    '\x79\x81\x82\x83\x84\x85\x86\x87\x88\x89\x91\x92\x93\x94\x95\x96' .
    '\x97\x98\x99\xA2\xA3\xA4\xA5\xA6\xA7\xA8\xA9\xC0\x4F\xD0\xA1\x07' .
    '\x20\x21\x22\x23\x24\x15\x06\x17\x28\x29\x2A\x2B\x2C\x09\x0A\x1B' .
    '\x30\x31\x1A\x33\x34\x35\x36\x08\x38\x39\x3A\x3B\x04\x14\x3E\xFF' .
    '\x41\xAA\x4A\xB1\x9F\xB2\x6A\xB5\xBD\xB4\x9A\x8A\x5F\xCA\xAF\xBC' .
    '\x90\x8F\xEA\xFA\xBE\xA0\xB6\xB3\x9D\xDA\x9B\x8B\xB7\xB8\xB9\xAB' .
    '\x64\x65\x62\x66\x63\x67\x9E\x68\x74\x71\x72\x73\x78\x75\x76\x77' .
    '\xAC\x69\xED\xEE\xEB\xEF\xEC\xBF\x80\xFD\xFE\xFB\xFC\xAD\xAE\x59' .
    '\x44\x45\x42\x46\x43\x47\x9C\x48\x54\x51\x52\x53\x58\x55\x56\x57' .
    '\x8C\x49\xCD\xCE\xCB\xCF\xCC\xE1\x70\xDD\xDE\xDB\xDC\x8D\x8E\xDF';

    my $ebcdic_string = $ascii_string;
    eval '$ebcdic_string =~ tr/\000-\377/' . $cp_037 . '/';

To convert from EBCDIC 037 to ASCII just reverse the order of the tr///
arguments like so:

    my $ascii_string = $ebcdic_string;
    eval '$ascii_string =~ tr/' . $cp_037 . '/\000-\377/';

Similarly one could take the output of the third numbers column from recipe 2
to obtain a C<$cp_1047> table.  The fourth numbers column of the output from
recipe 2 could provide a C<$cp_posix_bc> table suitable for transcoding as
well.

If you wanted to see the inverse tables, you would first have to sort on the
desired numbers column as in recipes 4, 5 or 6, then take the output of the
first numbers column.

=head2 iconv

XPG operability often implies the presence of an I<iconv> utility
available from the shell or from the C library.  Consult your system's
documentation for information on iconv.

On OS/390 or z/OS see the iconv(1) manpage.  One way to invoke the iconv
shell utility from within perl would be to:

    # OS/390 or z/OS example
    $ascii_data = `echo '$ebcdic_data'| iconv -f IBM-1047 -t ISO8859-1`

or the inverse map:

    # OS/390 or z/OS example
    $ebcdic_data = `echo '$ascii_data'| iconv -f ISO8859-1 -t IBM-1047`

For other perl-based conversion options see the Convert::* modules on CPAN.

=head2 C RTL

The OS/390 and z/OS C run-time libraries provide _atoe() and _etoa() functions.

=head1 OPERATOR DIFFERENCES

The C<..> range operator treats certain character ranges with
care on EBCDIC platforms.  For example the following array
will have twenty six elements on either an EBCDIC platform
or an ASCII platform:

    @alphabet = ('A'..'Z');   #  $#alphabet == 25

The bitwise operators such as & ^ | may return different results
when operating on string or character data in a perl program running
on an EBCDIC platform than when run on an ASCII platform.  Here is
an example adapted from the one in L<perlop>:

    # EBCDIC-based examples
    print "j p \n" ^ " a h";                      # prints "JAPH\n"
    print "JA" | "  ph\n";                        # prints "japh\n"
    print "JAPH\nJunk" & "\277\277\277\277\277";  # prints "japh\n";
    print 'p N$' ^ " E<H\n";                      # prints "Perl\n";

An interesting property of the 32 C0 control characters
in the ASCII table is that they can "literally" be constructed
as control characters in perl, e.g. C<(chr(0)> eq C<\c@>)>
C<(chr(1)> eq C<\cA>)>, and so on.  Perl on EBCDIC platforms has been
ported to take C<\c@> to chr(0) and C<\cA> to chr(1), etc. as well, but the
thirty three characters that result depend on which code page you are
using.  The table below uses the standard acronyms for the controls.
The POSIX-BC and 1047 sets are
identical throughout this range and differ from the 0037 set at only
one spot (21 decimal).  Note that the C<LINE FEED> character
may be generated by C<\cJ> on ASCII platforms but by C<\cU> on 1047 or POSIX-BC
platforms and cannot be generated as a C<"\c.letter."> control character on
0037 platforms.  Note also that C<\c\> cannot be the final element in a string
or regex, as it will absorb the terminator.   But C<\c\I<X>> is a C<FILE
SEPARATOR> concatenated with I<X> for all I<X>.

 chr   ord   8859-1    0037    1047 && POSIX-BC
 -----------------------------------------------------------------------
 \c?   127   <DEL>       "            "
 \c@     0   <NUL>     <NUL>        <NUL>
 \cA     1   <SOH>     <SOH>        <SOH>
 \cB     2   <STX>     <STX>        <STX>
 \cC     3   <ETX>     <ETX>        <ETX>
 \cD     4   <EOT>     <ST>         <ST>
 \cE     5   <ENQ>     <HT>         <HT>
 \cF     6   <ACK>     <SSA>        <SSA>
 \cG     7   <BEL>     <DEL>        <DEL>
 \cH     8   <BS>      <EPA>        <EPA>
 \cI     9   <HT>      <RI>         <RI>
 \cJ    10   <LF>      <SS2>        <SS2>
 \cK    11   <VT>      <VT>         <VT>
 \cL    12   <FF>      <FF>         <FF>
 \cM    13   <CR>      <CR>         <CR>
 \cN    14   <SO>      <SO>         <SO>
 \cO    15   <SI>      <SI>         <SI>
 \cP    16   <DLE>     <DLE>        <DLE>
 \cQ    17   <DC1>     <DC1>        <DC1>
 \cR    18   <DC2>     <DC2>        <DC2>
 \cS    19   <DC3>     <DC3>        <DC3>
 \cT    20   <DC4>     <OSC>        <OSC>
 \cU    21   <NAK>     <NEL>        <LF>              **
 \cV    22   <SYN>     <BS>         <BS>
 \cW    23   <ETB>     <ESA>        <ESA>
 \cX    24   <CAN>     <CAN>        <CAN>
 \cY    25   <EOM>     <EOM>        <EOM>
 \cZ    26   <SUB>     <PU2>        <PU2>
 \c[    27   <ESC>     <SS3>        <SS3>
 \c\X   28   <FS>X     <FS>X        <FS>X
 \c]    29   <GS>      <GS>         <GS>
 \c^    30   <RS>      <RS>         <RS>
 \c_    31   <US>      <US>         <US>

=head1 FUNCTION DIFFERENCES

=over 8

=item chr()

chr() must be given an EBCDIC code number argument to yield a desired
character return value on an EBCDIC platform.  For example:

    $CAPITAL_LETTER_A = chr(193);

=item ord()

ord() will return EBCDIC code number values on an EBCDIC platform.
For example:

    $the_number_193 = ord("A");

=item pack()

The c and C templates for pack() are dependent upon character set
encoding.  Examples of usage on EBCDIC include:

    $foo = pack("CCCC",193,194,195,196);
    # $foo eq "ABCD"
    $foo = pack("C4",193,194,195,196);
    # same thing

    $foo = pack("ccxxcc",193,194,195,196);
    # $foo eq "AB\0\0CD"

=item print()

One must be careful with scalars and strings that are passed to
print that contain ASCII encodings.  One common place
for this to occur is in the output of the MIME type header for
CGI script writing.  For example, many perl programming guides
recommend something similar to:

    print "Content-type:\ttext/html\015\012\015\012";
    # this may be wrong on EBCDIC

Under the IBM OS/390 USS Web Server or WebSphere on z/OS for example
you should instead write that as:

    print "Content-type:\ttext/html\r\n\r\n"; # OK for DGW et al

That is because the translation from EBCDIC to ASCII is done
by the web server in this case (such code will not be appropriate for
the Macintosh however).  Consult your web server's documentation for
further details.

=item printf()

The formats that can convert characters to numbers and vice versa
will be different from their ASCII counterparts when executed
on an EBCDIC platform.  Examples include:

    printf("%c%c%c",193,194,195);  # prints ABC

=item sort()

EBCDIC sort results may differ from ASCII sort results especially for
mixed case strings.  This is discussed in more detail below.

=item sprintf()

See the discussion of printf() above.  An example of the use
of sprintf would be:

    $CAPITAL_LETTER_A = sprintf("%c",193);

=item unpack()

See the discussion of pack() above.

=back

=head1 REGULAR EXPRESSION DIFFERENCES

As of perl 5.005_03 the letter range regular expressions such as
[A-Z] and [a-z] have been especially coded to not pick up gap
characters.  For example, characters such as E<ocirc> C<o WITH CIRCUMFLEX>
that lie between I and J would not be matched by the
regular expression range C</[H-K]/>.  This works in
the other direction, too, if either of the range end points is
explicitly numeric: C<[\x89-\x91]> will match C<\x8e>, even
though C<\x89> is C<i> and C<\x91 > is C<j>, and C<\x8e>
is a gap character from the alphabetic viewpoint.

If you do want to match the alphabet gap characters in a single octet
regular expression try matching the hex or octal code such
as C</\313/> on EBCDIC or C</\364/> on ASCII platforms to
have your regular expression match C<o WITH CIRCUMFLEX>.

Another construct to be wary of is the inappropriate use of hex or
octal constants in regular expressions.  Consider the following
set of subs:

    sub is_c0 {
        my $char = substr(shift,0,1);
        $char =~ /[\000-\037]/;
    }

    sub is_print_ascii {
        my $char = substr(shift,0,1);
        $char =~ /[\040-\176]/;
    }

    sub is_delete {
        my $char = substr(shift,0,1);
        $char eq "\177";
    }

    sub is_c1 {
        my $char = substr(shift,0,1);
        $char =~ /[\200-\237]/;
    }

    sub is_latin_1 {
        my $char = substr(shift,0,1);
        $char =~ /[\240-\377]/;
    }

The above would be adequate if the concern was only with numeric code points.
However, the concern may be with characters rather than code points
and on an EBCDIC platform it may be desirable for constructs such as
C<if (is_print_ascii("A")) {print "A is a printable character\n";}> to print
out the expected message.  One way to represent the above collection
of character classification subs that is capable of working across the
four coded character sets discussed in this document is as follows:

    sub Is_c0 {
        my $char = substr(shift,0,1);
        if (ord('^')==94)  { # ascii
            return $char =~ /[\000-\037]/;
        }
        if (ord('^')==176) { # 0037
            return $char =~ /[\000-\003\067\055-\057\026\005\045\013-\023\074\075\062\046\030\031\077\047\034-\037]/;
        }
        if (ord('^')==95 || ord('^')==106) { # 1047 || posix-bc
            return $char =~ /[\000-\003\067\055-\057\026\005\025\013-\023\074\075\062\046\030\031\077\047\034-\037]/;
        }
    }

    sub Is_print_ascii {
        my $char = substr(shift,0,1);
        $char =~ /[ !"\#\$%&'()*+,\-.\/0-9:;<=>?\@A-Z[\\\]^_`a-z{|}~]/;
    }

    sub Is_delete {
        my $char = substr(shift,0,1);
        if (ord('^')==94)  { # ascii
            return $char eq "\177";
        }
        else  {              # ebcdic
            return $char eq "\007";
        }
    }

    sub Is_c1 {
        my $char = substr(shift,0,1);
        if (ord('^')==94)  { # ascii
            return $char =~ /[\200-\237]/;
        }
        if (ord('^')==176) { # 0037
            return $char =~ /[\040-\044\025\006\027\050-\054\011\012\033\060\061\032\063-\066\010\070-\073\040\024\076\377]/;
        }
        if (ord('^')==95)  { # 1047
            return $char =~ /[\040-\045\006\027\050-\054\011\012\033\060\061\032\063-\066\010\070-\073\040\024\076\377]/;
        }
        if (ord('^')==106) { # posix-bc
            return $char =~
              /[\040-\045\006\027\050-\054\011\012\033\060\061\032\063-\066\010\070-\073\040\024\076\137]/;
        }
    }

    sub Is_latin_1 {
        my $char = substr(shift,0,1);
        if (ord('^')==94)  { # ascii
            return $char =~ /[\240-\377]/;
        }
        if (ord('^')==176) { # 0037
            return $char =~
              /[\101\252\112\261\237\262\152\265\275\264\232\212\137\312\257\274\220\217\352\372\276\240\266\263\235\332\233\213\267\270\271\253\144\145\142\146\143\147\236\150\164\161-\163\170\165-\167\254\151\355\356\353\357\354\277\200\375\376\373\374\255\256\131\104\105\102\106\103\107\234\110\124\121-\123\130\125-\127\214\111\315\316\313\317\314\341\160\335\336\333\334\215\216\337]/;
        }
        if (ord('^')==95)  { # 1047
            return $char =~
              /[\101\252\112\261\237\262\152\265\273\264\232\212\260\312\257\274\220\217\352\372\276\240\266\263\235\332\233\213\267\270\271\253\144\145\142\146\143\147\236\150\164\161-\163\170\165-\167\254\151\355\356\353\357\354\277\200\375\376\373\374\272\256\131\104\105\102\106\103\107\234\110\124\121-\123\130\125-\127\214\111\315\316\313\317\314\341\160\335\336\333\334\215\216\337]/;
        }
        if (ord('^')==106) { # posix-bc
            return $char =~
              /[\101\252\260\261\237\262\320\265\171\264\232\212\272\312\257\241\220\217\352\372\276\240\266\263\235\332\233\213\267\270\271\253\144\145\142\146\143\147\236\150\164\161-\163\170\165-\167\254\151\355\356\353\357\354\277\200\340\376\335\374\255\256\131\104\105\102\106\103\107\234\110\124\121-\123\130\125-\127\214\111\315\316\313\317\314\341\160\300\336\333\334\215\216\337]/;
        }
    }

Note however that only the C<Is_ascii_print()> sub is really independent
of coded character set.  Another way to write C<Is_latin_1()> would be
to use the characters in the range explicitly:

    sub Is_latin_1 {
        my $char = substr(shift,0,1);
        $char =~ /[ ¡¢£¤¥¦§¨©ª«¬®¯°±²³´µ¶·¸¹º»¼½¾¿ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿ]/;
    }

Although that form may run into trouble in network transit (due to the
presence of 8 bit characters) or on non ISO-Latin character sets.

=head1 SOCKETS

Most socket programming assumes ASCII character encodings in network
byte order.  Exceptions can include CGI script writing under a
host web server where the server may take care of translation for you.
Most host web servers convert EBCDIC data to ISO-8859-1 or Unicode on
output.

=head1 SORTING

One big difference between ASCII-based character sets and EBCDIC ones
are the relative positions of upper and lower case letters and the
letters compared to the digits.  If sorted on an ASCII-based platform the
two-letter abbreviation for a physician comes before the two letter
abbreviation for drive; that is:

 @sorted = sort(qw(Dr. dr.));  # @sorted holds ('Dr.','dr.') on ASCII,
                                  # but ('dr.','Dr.') on EBCDIC

The property of lowercase before uppercase letters in EBCDIC is
even carried to the Latin 1 EBCDIC pages such as 0037 and 1047.
An example would be that E<Euml> C<E WITH DIAERESIS> (203) comes
before E<euml> C<e WITH DIAERESIS> (235) on an ASCII platform, but
the latter (83) comes before the former (115) on an EBCDIC platform.
(Astute readers will note that the uppercase version of E<szlig>
C<SMALL LETTER SHARP S> is simply "SS" and that the upper case version of
E<yuml> C<y WITH DIAERESIS> is not in the 0..255 range but it is
at U+x0178 in Unicode, or C<"\x{178}"> in a Unicode enabled Perl).

The sort order will cause differences between results obtained on
ASCII platforms versus EBCDIC platforms.  What follows are some suggestions
on how to deal with these differences.

=head2 Ignore ASCII vs. EBCDIC sort differences.

This is the least computationally expensive strategy.  It may require
some user education.

=head2 MONO CASE then sort data.

In order to minimize the expense of mono casing mixed-case text, try to
C<tr///> towards the character set case most employed within the data.
If the data are primarily UPPERCASE non Latin 1 then apply tr/[a-z]/[A-Z]/
then sort().  If the data are primarily lowercase non Latin 1 then
apply tr/[A-Z]/[a-z]/ before sorting.  If the data are primarily UPPERCASE
and include Latin-1 characters then apply:

   tr/[a-z]/[A-Z]/;
   tr/[àáâãäåæçèéêëìíîïðñòóôõöøùúûüýþ]/[ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖØÙÚÛÜÝÞ/;
   s/ß/SS/g;

then sort().  Do note however that such Latin-1 manipulation does not
address the E<yuml> C<y WITH DIAERESIS> character that will remain at
code point 255 on ASCII platforms, but 223 on most EBCDIC platforms
where it will sort to a place less than the EBCDIC numerals.  With a
Unicode-enabled Perl you might try:

    tr/^?/\x{178}/;

The strategy of mono casing data before sorting does not preserve the case
of the data and may not be acceptable for that reason.

=head2 Convert, sort data, then re convert.

This is the most expensive proposition that does not employ a network
connection.

=head2 Perform sorting on one type of platform only.

This strategy can employ a network connection.  As such
it would be computationally expensive.

=head1 TRANSFORMATION FORMATS

There are a variety of ways of transforming data with an intra character set
mapping that serve a variety of purposes.  Sorting was discussed in the
previous section and a few of the other more popular mapping techniques are
discussed next.

=head2 URL decoding and encoding

Note that some URLs have hexadecimal ASCII code points in them in an
attempt to overcome character or protocol limitation issues.  For example
the tilde character is not on every keyboard hence a URL of the form:

    http://www.pvhp.com/~pvhp/

may also be expressed as either of:

    http://www.pvhp.com/%7Epvhp/

    http://www.pvhp.com/%7epvhp/

where 7E is the hexadecimal ASCII code point for '~'.  Here is an example
of decoding such a URL under CCSID 1047:

    $url = 'http://www.pvhp.com/%7Epvhp/';
    # this array assumes code page 1047
    my @a2e_1047 = (
          0,  1,  2,  3, 55, 45, 46, 47, 22,  5, 21, 11, 12, 13, 14, 15,
         16, 17, 18, 19, 60, 61, 50, 38, 24, 25, 63, 39, 28, 29, 30, 31,
         64, 90,127,123, 91,108, 80,125, 77, 93, 92, 78,107, 96, 75, 97,
        240,241,242,243,244,245,246,247,248,249,122, 94, 76,126,110,111,
        124,193,194,195,196,197,198,199,200,201,209,210,211,212,213,214,
        215,216,217,226,227,228,229,230,231,232,233,173,224,189, 95,109,
        121,129,130,131,132,133,134,135,136,137,145,146,147,148,149,150,
        151,152,153,162,163,164,165,166,167,168,169,192, 79,208,161,  7,
         32, 33, 34, 35, 36, 37,  6, 23, 40, 41, 42, 43, 44,  9, 10, 27,
         48, 49, 26, 51, 52, 53, 54,  8, 56, 57, 58, 59,  4, 20, 62,255,
         65,170, 74,177,159,178,106,181,187,180,154,138,176,202,175,188,
        144,143,234,250,190,160,182,179,157,218,155,139,183,184,185,171,
        100,101, 98,102, 99,103,158,104,116,113,114,115,120,117,118,119,
        172,105,237,238,235,239,236,191,128,253,254,251,252,186,174, 89,
         68, 69, 66, 70, 67, 71,156, 72, 84, 81, 82, 83, 88, 85, 86, 87,
        140, 73,205,206,203,207,204,225,112,221,222,219,220,141,142,223
    );
    $url =~ s/%([0-9a-fA-F]{2})/pack("c",$a2e_1047[hex($1)])/ge;

Conversely, here is a partial solution for the task of encoding such
a URL under the 1047 code page:

    $url = 'http://www.pvhp.com/~pvhp/';
    # this array assumes code page 1047
    my @e2a_1047 = (
          0,  1,  2,  3,156,  9,134,127,151,141,142, 11, 12, 13, 14, 15,
         16, 17, 18, 19,157, 10,  8,135, 24, 25,146,143, 28, 29, 30, 31,
        128,129,130,131,132,133, 23, 27,136,137,138,139,140,  5,  6,  7,
        144,145, 22,147,148,149,150,  4,152,153,154,155, 20, 21,158, 26,
         32,160,226,228,224,225,227,229,231,241,162, 46, 60, 40, 43,124,
         38,233,234,235,232,237,238,239,236,223, 33, 36, 42, 41, 59, 94,
         45, 47,194,196,192,193,195,197,199,209,166, 44, 37, 95, 62, 63,
        248,201,202,203,200,205,206,207,204, 96, 58, 35, 64, 39, 61, 34,
        216, 97, 98, 99,100,101,102,103,104,105,171,187,240,253,254,177,
        176,106,107,108,109,110,111,112,113,114,170,186,230,184,198,164,
        181,126,115,116,117,118,119,120,121,122,161,191,208, 91,222,174,
        172,163,165,183,169,167,182,188,189,190,221,168,175, 93,180,215,
        123, 65, 66, 67, 68, 69, 70, 71, 72, 73,173,244,246,242,243,245,
        125, 74, 75, 76, 77, 78, 79, 80, 81, 82,185,251,252,249,250,255,
         92,247, 83, 84, 85, 86, 87, 88, 89, 90,178,212,214,210,211,213,
         48, 49, 50, 51, 52, 53, 54, 55, 56, 57,179,219,220,217,218,159
    );
    # The following regular expression does not address the
    # mappings for: ('.' => '%2E', '/' => '%2F', ':' => '%3A')
    $url =~ s/([\t "#%&\(\),;<=>\?\@\[\\\]^`{|}~])/sprintf("%%%02X",$e2a_1047[ord($1)])/ge;

where a more complete solution would split the URL into components
and apply a full s/// substitution only to the appropriate parts.

In the remaining examples a @e2a or @a2e array may be employed
but the assignment will not be shown explicitly.  For code page 1047
you could use the @a2e_1047 or @e2a_1047 arrays just shown.

=head2 uu encoding and decoding

The C<u> template to pack() or unpack() will render EBCDIC data in EBCDIC
characters equivalent to their ASCII counterparts.  For example, the
following will print "Yes indeed\n" on either an ASCII or EBCDIC computer:

    $all_byte_chrs = '';
    for (0..255) { $all_byte_chrs .= chr($_); }
    $uuencode_byte_chrs = pack('u', $all_byte_chrs);
    ($uu = <<'ENDOFHEREDOC') =~ s/^\s*//gm;
    M``$"`P0%!@<("0H+#`T.#Q`1$A,4%187&!D:&QP='A\@(2(C)"4F)R@I*BLL
    M+2XO,#$R,S0U-C<X.3H[/#T^/T!!0D-$149'2$E*2TQ-3D]045)35%565UA9
    M6EM<75Y?8&%B8V1E9F=H:6IK;&UN;W!Q<G-T=79W>'EZ>WQ]?G^`@8*#A(6&
    MAXB)BHN,C8Z/D)&2DY25EI>8F9J;G)V>GZ"AHJ.DI::GJ*FJJZRMKJ^PL;*S
    MM+6VM[BYNKN\O;Z_P,'"P\3%QL?(R<K+S,W.S]#1TM/4U=;7V-G:V]S=WM_@
    ?X>+CY.7FY^CIZNOL[>[O\/'R\_3U]O?X^?K[_/W^_P``
    ENDOFHEREDOC
    if ($uuencode_byte_chrs eq $uu) {
        print "Yes ";
    }
    $uudecode_byte_chrs = unpack('u', $uuencode_byte_chrs);
    if ($uudecode_byte_chrs eq $all_byte_chrs) {
        print "indeed\n";
    }

Here is a very spartan uudecoder that will work on EBCDIC provided
that the @e2a array is filled in appropriately:

    #!/usr/local/bin/perl
    @e2a = ( # this must be filled in
           );
    $_ = <> until ($mode,$file) = /^begin\s*(\d*)\s*(\S*)/;
    open(OUT, "> $file") if $file ne "";
    while(<>) {
        last if /^end/;
        next if /[a-z]/;
        next unless int(((($e2a[ord()] - 32 ) & 077) + 2) / 3) ==
            int(length() / 4);
        print OUT unpack("u", $_);
    }
    close(OUT);
    chmod oct($mode), $file;


=head2 Quoted-Printable encoding and decoding

On ASCII-encoded platforms it is possible to strip characters outside of
the printable set using:

    # This QP encoder works on ASCII only
    $qp_string =~ s/([=\x00-\x1F\x80-\xFF])/sprintf("=%02X",ord($1))/ge;

Whereas a QP encoder that works on both ASCII and EBCDIC platforms
would look somewhat like the following (where the EBCDIC branch @e2a
array is omitted for brevity):

    if (ord('A') == 65) {    # ASCII
        $delete = "\x7F";    # ASCII
        @e2a = (0 .. 255)    # ASCII to ASCII identity map
    }
    else {                   # EBCDIC
        $delete = "\x07";    # EBCDIC
        @e2a =               # EBCDIC to ASCII map (as shown above)
    }
    $qp_string =~
      s/([^ !"\#\$%&'()*+,\-.\/0-9:;<>?\@A-Z[\\\]^_`a-z{|}~$delete])/sprintf("=%02X",$e2a[ord($1)])/ge;

(although in production code the substitutions might be done
in the EBCDIC branch with the @e2a array and separately in the
ASCII branch without the expense of the identity map).

Such QP strings can be decoded with:

    # This QP decoder is limited to ASCII only
    $string =~ s/=([0-9A-Fa-f][0-9A-Fa-f])/chr hex $1/ge;
    $string =~ s/=[\n\r]+$//;

Whereas a QP decoder that works on both ASCII and EBCDIC platforms
would look somewhat like the following (where the @a2e array is
omitted for brevity):

    $string =~ s/=([0-9A-Fa-f][0-9A-Fa-f])/chr $a2e[hex $1]/ge;
    $string =~ s/=[\n\r]+$//;

=head2 Caesarean ciphers

The practice of shifting an alphabet one or more characters for encipherment
dates back thousands of years and was explicitly detailed by Gaius Julius
Caesar in his B<Gallic Wars> text.  A single alphabet shift is sometimes
referred to as a rotation and the shift amount is given as a number $n after
the string 'rot' or "rot$n".  Rot0 and rot26 would designate identity maps
on the 26-letter English version of the Latin alphabet.  Rot13 has the
interesting property that alternate subsequent invocations are identity maps
(thus rot13 is its own non-trivial inverse in the group of 26 alphabet
rotations).  Hence the following is a rot13 encoder and decoder that will
work on ASCII and EBCDIC platforms:

    #!/usr/local/bin/perl

    while(<>){
        tr/n-za-mN-ZA-M/a-zA-Z/;
        print;
    }

In one-liner form:

    perl -ne 'tr/n-za-mN-ZA-M/a-zA-Z/;print'


=head1 Hashing order and checksums

To the extent that it is possible to write code that depends on
hashing order there may be differences between hashes as stored
on an ASCII-based platform and hashes stored on an EBCDIC-based platform.
XXX

=head1 I18N AND L10N

Internationalization (I18N) and localization (L10N) are supported at least
in principle even on EBCDIC platforms.  The details are system-dependent
and discussed under the L<perlebcdic/OS ISSUES> section below.

=head1 MULTI-OCTET CHARACTER SETS

Perl may work with an internal UTF-EBCDIC encoding form for wide characters
on EBCDIC platforms in a manner analogous to the way that it works with
the UTF-8 internal encoding form on ASCII based platforms.

Legacy multi byte EBCDIC code pages XXX.

=head1 OS ISSUES

There may be a few system-dependent issues
of concern to EBCDIC Perl programmers.

=head2 OS/400

=over 8

=item PASE

The PASE environment is a runtime environment for OS/400 that can run
executables built for PowerPC AIX in OS/400; see L<perlos400>.  PASE
is ASCII-based, not EBCDIC-based as the ILE.

=item IFS access

XXX.

=back

=head2 OS/390, z/OS

Perl runs under Unix Systems Services or USS.

=over 8

=item chcp

B<chcp> is supported as a shell utility for displaying and changing
one's code page.  See also L<chcp(1)>.

=item dataset access

For sequential data set access try:

    my @ds_records = `cat //DSNAME`;

or:

    my @ds_records = `cat //'HLQ.DSNAME'`;

See also the OS390::Stdio module on CPAN.

=item OS/390, z/OS iconv

B<iconv> is supported as both a shell utility and a C RTL routine.
See also the iconv(1) and iconv(3) manual pages.

=item locales

On OS/390 or z/OS see L<locale> for information on locales.  The L10N files
are in F</usr/nls/locale>.  $Config{d_setlocale} is 'define' on OS/390
or z/OS.

=back

=head2 POSIX-BC?

XXX.

=head1 BUGS

This pod document contains literal Latin 1 characters and may encounter
translation difficulties.  In particular one popular nroff implementation
was known to strip accented characters to their unaccented counterparts
while attempting to view this document through the B<pod2man> program
(for example, you may see a plain C<y> rather than one with a diaeresis
as in E<yuml>).  Another nroff truncated the resultant manpage at
the first occurrence of 8 bit characters.

Not all shells will allow multiple C<-e> string arguments to perl to
be concatenated together properly as recipes 0, 2, 4, 5, and 6 might
seem to imply.

=head1 SEE ALSO

L<perllocale>, L<perlfunc>, L<perlunicode>, L<utf8>.

=head1 REFERENCES

L<http://anubis.dkuug.dk/i18n/charmaps>

L<http://www.unicode.org/>

L<http://www.unicode.org/unicode/reports/tr16/>

L<http://www.wps.com/projects/codes/>
B<ASCII: American Standard Code for Information Infiltration> Tom Jennings,
September 1999.

B<The Unicode Standard, Version 3.0> The Unicode Consortium, Lisa Moore ed.,
ISBN 0-201-61633-5, Addison Wesley Developers Press, February 2000.

B<CDRA: IBM - Character Data Representation Architecture -
Reference and Registry>, IBM SC09-2190-00, December 1996.

"Demystifying Character Sets", Andrea Vine, Multilingual Computing
& Technology, B<#26 Vol. 10 Issue 4>, August/September 1999;
ISSN 1523-0309; Multilingual Computing Inc. Sandpoint ID, USA.

B<Codes, Ciphers, and Other Cryptic and Clandestine Communication>
Fred B. Wrixon, ISBN 1-57912-040-7, Black Dog & Leventhal Publishers,
1998.

L<http://www.bobbemer.com/P-BIT.HTM>
B<IBM - EBCDIC and the P-bit; The biggest Computer Goof Ever> Robert Bemer.

=head1 HISTORY

15 April 2001: added UTF-8 and UTF-EBCDIC to main table, pvhp.

=head1 AUTHOR

Peter Prymmer pvhp@best.com wrote this in 1999 and 2000
with CCSID 0819 and 0037 help from Chris Leach and
AndrE<eacute> Pirard A.Pirard@ulg.ac.be as well as POSIX-BC
help from Thomas Dorner Thomas.Dorner@start.de.
Thanks also to Vickie Cooper, Philip Newton, William Raffloer, and
Joe Smith.  Trademarks, registered trademarks, service marks and
registered service marks used in this document are the property of
their respective owners.