=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.

=head1 COMMON CHARACTER CODE SETS

=head2 ASCII

The American Standard Code for Information Interchange is a set of
integers running from 0 to 127 (decimal) that imply character 
interpretation by the display and other system(s) 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 a "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 slightly different single and multi byte 
coded character sets that are different from ASCII or ISO 8859-1 
and 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.  Leading
zero digits in CCSID numbers within this document are insignificant.
E.g. CCSID 0037 may be referred to as 37 in places.

=head2 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:

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

=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 37 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 seem to be related to case-insensitive matching:
for example, C<< /[\x{131}]/ >> (LATIN SMALL LETTER DOTLESS I) does
not match "I" case-insensitively, as it should under Unicode.
(The match succeeds in ASCII-derived platforms.)

=item *

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

=back

=head2 Unicode and UTF

UTF is a Unicode Transformation Format.  UTF-8 is a Unicode conforming
representation of the Unicode standard that looks very much like ASCII.
UTF-EBCDIC is an attempt to represent Unicode characters in an EBCDIC
transparent manner.

=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

	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 two files containing "Hello World!\n" in ASCII, CP 37 EBCDIC,
ISO 8859-1 (Latin-1) (in this example identical to ASCII) respective
UTF-EBCDIC (in this example identical to normal EBCDIC).  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 non-printing control character names as well as the Latin 1 
extensions to ASCII have been labelled with character names roughly 
corresponding to I<The Unicode Standard, Version 3.0> 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 (the C<charnames> pragma names unfortunately do 
not list explicit names for the C0 or C1 control characters).  The 
"names" of the C1 control set (128..159 in ISO 8859-1) listed here are 
somewhat arbitrary.  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 version 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(/(.{33})(\d+)\s+(\d+)\s+(\d+)\s+(\d+)/)' \
     -e '{printf("%s%-9o%-9o%-9o%o\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 (/(.{33})(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\.?(\d*)\s+(\d+)\.?(\d*)/)  {
            if ($7 ne '' && $9 ne '') {
                printf("%s%-9o%-9o%-9o%-9o%-3o.%-5o%-3o.%o\n",$1,$2,$3,$4,$5,$6,$7,$8,$9);
            }
            elsif ($7 ne '') {
                printf("%s%-9o%-9o%-9o%-9o%-3o.%-5o%o\n",$1,$2,$3,$4,$5,$6,$7,$8);
            }
            else {
                printf("%s%-9o%-9o%-9o%-9o%-9o%o\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(/(.{33})(\d+)\s+(\d+)\s+(\d+)\s+(\d+)/)' \
     -e '{printf("%s%-9X%-9X%-9X%X\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 (/(.{33})(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\.?(\d*)\s+(\d+)\.?(\d*)/)  {
            if ($7 ne '' && $9 ne '') {
                printf("%s%-9X%-9X%-9X%-9X%-2X.%-6X%-2X.%X\n",$1,$2,$3,$4,$5,$6,$7,$8,$9);
            }
            elsif ($7 ne '') {
                printf("%s%-9X%-9X%-9X%-9X%-2X.%-6X%X\n",$1,$2,$3,$4,$5,$6,$7,$8);
            }
            else {
                printf("%s%-9X%-9X%-9X%-9X%-9X%X\n",$1,$2,$3,$4,$5,$6,$8);
            }
        }
    }


                                                                     incomp-  incomp-
                                 8859-1                              lete     lete
    chr                          0819     0037     1047     POSIX-BC UTF-8    UTF-EBCDIC
    ------------------------------------------------------------------------------------
    <NULL>                       0        0        0        0        0        0 
    <START OF HEADING>           1        1        1        1        1        1
    <START OF TEXT>              2        2        2        2        2        2
    <END OF TEXT>                3        3        3        3        3        3
    <END OF TRANSMISSION>        4        55       55       55       4        55 
    <ENQUIRY>                    5        45       45       45       5        45 
    <ACKNOWLEDGE>                6        46       46       46       6        46 
    <BELL>                       7        47       47       47       7        47 
    <BACKSPACE>                  8        22       22       22       8        22 
    <HORIZONTAL TABULATION>      9        5        5        5        9        5 
    <LINE FEED>                  10       37       21       21       10       21       ***
    <VERTICAL TABULATION>        11       11       11       11       11       11
    <FORM FEED>                  12       12       12       12       12       12
    <CARRIAGE RETURN>            13       13       13       13       13       13
    <SHIFT OUT>                  14       14       14       14       14       14
    <SHIFT IN>                   15       15       15       15       15       15
    <DATA LINK ESCAPE>           16       16       16       16       16       16
    <DEVICE CONTROL ONE>         17       17       17       17       17       17
    <DEVICE CONTROL TWO>         18       18       18       18       18       18
    <DEVICE CONTROL THREE>       19       19       19       19       19       19
    <DEVICE CONTROL FOUR>        20       60       60       60       20       60
    <NEGATIVE ACKNOWLEDGE>       21       61       61       61       21       61
    <SYNCHRONOUS IDLE>           22       50       50       50       22       50
    <END OF TRANSMISSION BLOCK>  23       38       38       38       23       38
    <CANCEL>                     24       24       24       24       24       24
    <END OF MEDIUM>              25       25       25       25       25       25
    <SUBSTITUTE>                 26       63       63       63       26       63
    <ESCAPE>                     27       39       39       39       27       39
    <FILE SEPARATOR>             28       28       28       28       28       28
    <GROUP SEPARATOR>            29       29       29       29       29       29
    <RECORD SEPARATOR>           30       30       30       30       30       30
    <UNIT SEPARATOR>             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      ###
    <DELETE>                     127      7        7        7        127      7
    <C1 0>                       128      32       32       32       194.128  32
    <C1 1>                       129      33       33       33       194.129  33
    <C1 2>                       130      34       34       34       194.130  34
    <C1 3>                       131      35       35       35       194.131  35
    <C1 4>                       132      36       36       36       194.132  36
    <C1 5>                       133      21       37       37       194.133  37       ***
    <C1 6>                       134      6        6        6        194.134  6
    <C1 7>                       135      23       23       23       194.135  23
    <C1 8>                       136      40       40       40       194.136  40
    <C1 9>                       137      41       41       41       194.137  41
    <C1 10>                      138      42       42       42       194.138  42
    <C1 11>                      139      43       43       43       194.139  43
    <C1 12>                      140      44       44       44       194.140  44
    <C1 13>                      141      9        9        9        194.141  9
    <C1 14>                      142      10       10       10       194.142  10
    <C1 15>                      143      27       27       27       194.143  27
    <C1 16>                      144      48       48       48       194.144  48
    <C1 17>                      145      49       49       49       194.145  49
    <C1 18>                      146      26       26       26       194.146  26
    <C1 19>                      147      51       51       51       194.147  51
    <C1 20>                      148      52       52       52       194.148  52
    <C1 21>                      149      53       53       53       194.149  53
    <C1 22>                      150      54       54       54       194.150  54
    <C1 23>                      151      8        8        8        194.151  8
    <C1 24>                      152      56       56       56       194.152  56
    <C1 25>                      153      57       57       57       194.153  57
    <C1 26>                      154      58       58       58       194.154  58
    <C1 27>                      155      59       59       59       194.155  59
    <C1 28>                      156      4        4        4        194.156  4
    <C1 29>                      157      20       20       20       194.157  20
    <C1 30>                      158      62       62       62       194.158  62
    <C1 31>                      159      255      255      95       194.159  255      ###
    <NON-BREAKING SPACE>         160      65       65       65       194.160  128.65
    <INVERTED EXCLAMATION MARK>  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 INDICATOR> 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 SIGN> 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(/.{33}\d{1,3}\s{6,8}\d{1,3}\s{6,8}\d{1,3}\s{6,8}\d{1,3}/)'\
     -e '{push(@l,$_)}' \
     -e 'END{print map{$_->[0]}' \
     -e '          sort{$a->[1] <=> $b->[1]}' \
     -e '          map{[$_,substr($_,42,3)]}@l;}' perlebcdic.pod

If you would rather see it in CCSID 1047 order then change the digit
42 in the last line to 51, like this:

=over 4

=item recipe 5

=back

    perl -ne 'if(/.{33}\d{1,3}\s{6,8}\d{1,3}\s{6,8}\d{1,3}\s{6,8}\d{1,3}/)'\
     -e '{push(@l,$_)}' \
     -e 'END{print map{$_->[0]}' \
     -e '          sort{$a->[1] <=> $b->[1]}' \
     -e '          map{[$_,substr($_,51,3)]}@l;}' perlebcdic.pod

If you would rather see it in POSIX-BC order then change the digit
51 in the last line to 60, like this:

=over 4

=item recipe 6

=back

    perl -ne 'if(/.{33}\d{1,3}\s{6,8}\d{1,3}\s{6,8}\d{1,3}\s{6,8}\d{1,3}/)'\
     -e '{push(@l,$_)}' \
     -e 'END{print map{$_->[0]}' \
     -e '          sort{$a->[1] <=> $b->[1]}' \
     -e '          map{[$_,substr($_,60,3)]}@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 machines
from either a CCSID 0037, a 1047, or a POSIX-BC EBCDIC machine 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 machine) 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 order hence the EBCDIC columns 
provide easy to use ASCII to EBCDIC operations that are also easily 
reversed.

For example, to convert ASCII to code page 037 take the output of the second 
column from the output of recipe 0 (modified to add \\ characters) and use 
it in tr/// like so:

    $cp_037 = 
    '\000\001\002\003\234\011\206\177\227\215\216\013\014\015\016\017' .
    '\020\021\022\023\235\205\010\207\030\031\222\217\034\035\036\037' .
    '\200\201\202\203\204\012\027\033\210\211\212\213\214\005\006\007' .
    '\220\221\026\223\224\225\226\004\230\231\232\233\024\025\236\032' .
    '\040\240\342\344\340\341\343\345\347\361\242\056\074\050\053\174' .
    '\046\351\352\353\350\355\356\357\354\337\041\044\052\051\073\254' .
    '\055\057\302\304\300\301\303\305\307\321\246\054\045\137\076\077' .
    '\370\311\312\313\310\315\316\317\314\140\072\043\100\047\075\042' .
    '\330\141\142\143\144\145\146\147\150\151\253\273\360\375\376\261' .
    '\260\152\153\154\155\156\157\160\161\162\252\272\346\270\306\244' .
    '\265\176\163\164\165\166\167\170\171\172\241\277\320\335\336\256' .
    '\136\243\245\267\251\247\266\274\275\276\133\135\257\250\264\327' .
    '\173\101\102\103\104\105\106\107\110\111\255\364\366\362\363\365' .
    '\175\112\113\114\115\116\117\120\121\122\271\373\374\371\372\377' .
    '\134\367\123\124\125\126\127\130\131\132\262\324\326\322\323\325' .
    '\060\061\062\063\064\065\066\067\070\071\263\333\334\331\332\237' ;

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

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/\000-\377/' . $cp_037 . '/';

Similarly one could take the output of the third column from recipe 0 to
obtain a C<$cp_1047> table.  The fourth column of the output from recipe
0 could provide a C<$cp_posix_bc> table suitable for transcoding as well.

=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 machines.  For example the following array
will have twenty six elements on either an EBCDIC machine
or an ASCII machine:

    @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 machine than when run on an ASCII machine.  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<(chr(1) eq "\cA")>, and so on.  Perl on EBCDIC machines has been 
ported to take "\c@" to chr(0) and "\cA" to chr(1) as well, but the
thirty three characters that result depend on which code page you are
using.  The table below uses the character names from the previous table 
but with substitutions such as s/START OF/S.O./; s/END OF /E.O./; 
s/TRANSMISSION/TRANS./; s/TABULATION/TAB./; s/VERTICAL/VERT./; 
s/HORIZONTAL/HORIZ./; s/DEVICE CONTROL/D.C./; s/SEPARATOR/SEP./; 
s/NEGATIVE ACKNOWLEDGE/NEG. ACK./;.  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 "\cJ" on ASCII machines but by "\cU" on 1047 or POSIX-BC 
machines and cannot be generated as a C<"\c.letter."> control character on 
0037 machines.  Note also that "\c\\" maps to two characters
not one.

    chr   ord  8859-1               0037                1047 && POSIX-BC     
    ------------------------------------------------------------------------
    "\c?" 127  <DELETE>             "                   "              ***><
    "\c@"   0  <NULL>               <NULL>              <NULL>         ***><
    "\cA"   1  <S.O. HEADING>       <S.O. HEADING>      <S.O. HEADING> 
    "\cB"   2  <S.O. TEXT>          <S.O. TEXT>         <S.O. TEXT>
    "\cC"   3  <E.O. TEXT>          <E.O. TEXT>         <E.O. TEXT>
    "\cD"   4  <E.O. TRANS.>        <C1 28>             <C1 28> 
    "\cE"   5  <ENQUIRY>            <HORIZ. TAB.>       <HORIZ. TAB.>    
    "\cF"   6  <ACKNOWLEDGE>        <C1 6>              <C1 6>   
    "\cG"   7  <BELL>               <DELETE>            <DELETE>   
    "\cH"   8  <BACKSPACE>          <C1 23>             <C1 23>
    "\cI"   9  <HORIZ. TAB.>        <C1 13>             <C1 13>
    "\cJ"  10  <LINE FEED>          <C1 14>             <C1 14>
    "\cK"  11  <VERT. TAB.>         <VERT. TAB.>        <VERT. TAB.>
    "\cL"  12  <FORM FEED>          <FORM FEED>         <FORM FEED>    
    "\cM"  13  <CARRIAGE RETURN>    <CARRIAGE RETURN>   <CARRIAGE RETURN> 
    "\cN"  14  <SHIFT OUT>          <SHIFT OUT>         <SHIFT OUT>
    "\cO"  15  <SHIFT IN>           <SHIFT IN>          <SHIFT IN>
    "\cP"  16  <DATA LINK ESCAPE>   <DATA LINK ESCAPE>  <DATA LINK ESCAPE> 
    "\cQ"  17  <D.C. ONE>           <D.C. ONE>          <D.C. ONE>
    "\cR"  18  <D.C. TWO>           <D.C. TWO>          <D.C. TWO>
    "\cS"  19  <D.C. THREE>         <D.C. THREE>        <D.C. THREE> 
    "\cT"  20  <D.C. FOUR>          <C1 29>             <C1 29> 
    "\cU"  21  <NEG. ACK.>          <C1 5>              <LINE FEED>    ***
    "\cV"  22  <SYNCHRONOUS IDLE>   <BACKSPACE>         <BACKSPACE>
    "\cW"  23  <E.O. TRANS. BLOCK>  <C1 7>              <C1 7>
    "\cX"  24  <CANCEL>             <CANCEL>            <CANCEL>
    "\cY"  25  <E.O. MEDIUM>        <E.O. MEDIUM>       <E.O. MEDIUM>
    "\cZ"  26  <SUBSTITUTE>         <C1 18>             <C1 18>
    "\c["  27  <ESCAPE>             <C1 15>             <C1 15>
    "\c\\" 28  <FILE SEP.>\         <FILE SEP.>\        <FILE SEP.>\
    "\c]"  29  <GROUP SEP.>         <GROUP SEP.>        <GROUP SEP.>
    "\c^"  30  <RECORD SEP.>        <RECORD SEP.>       <RECORD SEP.>  ***><
    "\c_"  31  <UNIT SEP.>          <UNIT SEP.>         <UNIT SEP.>    ***><


=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 machine.  For example:

    $CAPITAL_LETTER_A = chr(193);

=item ord()

ord() will return EBCDIC code number values on an EBCDIC machine.
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 alia

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 machine.  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 expression 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 machines 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 machine 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) { # 37
            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) { # 37
            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) { # 37
            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 =~ /[†°¢£§•¶ß®©™´¨≠ÆØ∞±≤≥¥µ∂∑∏π∫ªºΩæø¿¡¬√ƒ≈∆«»… ÀÃÕŒœ–—“”‘’÷◊ÿŸ⁄€‹›ﬁﬂ‡·‚„‰ÂÊÁËÈÍÎÏÌÓÔÒÚÛÙıˆ˜¯˘˙˚¸˝˛ˇ]/;
    }

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 machine the
two letter abbreviation for a physician comes before the two letter
for drive, that is:

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

The property of lower case 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 machine, but 
the latter (83) comes before the former (115) on an EBCDIC machine.  
(Astute readers will note that the upper case 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 machines versus EBCDIC machines.  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 test 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/[‡·‚„‰ÂÊÁËÈÍÎÏÌÓÔÒÚÛÙıˆ¯˘˙˚¸˝˛]/[¿¡¬√ƒ≈∆«»… ÀÃÕŒœ–—“”‘’÷ÿŸ⁄€‹›ﬁ]/;
    s/ﬂ/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 machines, but 223 on most EBCDIC machines 
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 machine 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 machines 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 machines 
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 machines 
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 Caesarian 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 machines:

    #!/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 machine and hashes stored on an EBCDIC based machine.
XXX

=head1 I18N AND L10N

Internationalization(I18N) and localization(L10N) are supported at least 
in principle even on EBCDIC machines.  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 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>.

=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 VM/ESA?

XXX.

=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

http://anubis.dkuug.dk/i18n/charmaps

http://www.unicode.org/

http://www.unicode.org/unicode/reports/tr16/

http://www.wps.com/texts/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.

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.


