[p5sagit/p5-mst-13.2.git] / pod / perlebcdic.pod

=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 (yet).

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 is 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 Instute 
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.

=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, 
Portugese, 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
known as CCSID 819 (or sometimes 0819 or even 00819).

=head2 EBCDIC

Extended Binary Coded Decimal Interchange Code.  The EBCDIC acronym 
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 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.

=head2 13 variant characters

XXX.

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

=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 
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, 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.

=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 2.0> 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 "names" of the C1 control set 
(128..159 in ISO 8859-1) 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 pod2XXX translation to another format) through:

=over 4

=item recipe 0

=back

    perl -ne 'if(/(.{33})(\d+)\s+(\d+)\s+(\d+)\s+(\d+)/)' \
     -e '{printf("%s%-9o%-9o%-9o%-9o\n",$1,$2,$3,$4,$5)}' perlebcdic.pod

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

=over 4

=item recipe 1

=back

    perl -ne 'if(/(.{33})(\d+)\s+(\d+)\s+(\d+)\s+(\d+)/)' \
     -e '{printf("%s%-9X%-9X%-9X%-9X\n",$1,$2,$3,$4,$5)}' perlebcdic.pod


                                 8859-1
    chr                          0819     0037     1047     POSIX-BC
    ----------------------------------------------------------------
    <NULL>                       0        0        0        0 
    <START OF HEADING>           1        1        1        1
    <START OF TEXT>              2        2        2        2
    <END OF TEXT>                3        3        3        3
    <END OF TRANSMISSION>        4        55       55       55
    <ENQUIRY>                    5        45       45       45
    <ACKNOWLEDGE>                6        46       46       46
    <BELL>                       7        47       47       47
    <BACKSPACE>                  8        22       22       22
    <HORIZONTAL TABULATION>      9        5        5        5
    <LINE FEED>                  10       37       21       21  ***
    <VERTICAL TABULATION>        11       11       11       11
    <FORM FEED>                  12       12       12       12
    <CARRIAGE RETURN>            13       13       13       13
    <SHIFT OUT>                  14       14       14       14
    <SHIFT IN>                   15       15       15       15
    <DATA LINK ESCAPE>           16       16       16       16
    <DEVICE CONTROL ONE>         17       17       17       17
    <DEVICE CONTROL TWO>         18       18       18       18
    <DEVICE CONTROL THREE>       19       19       19       19
    <DEVICE CONTROL FOUR>        20       60       60       60
    <NEGATIVE ACKNOWLEDGE>       21       61       61       61
    <SYNCHRONOUS IDLE>           22       50       50       50
    <END OF TRANSMISSION BLOCK>  23       38       38       38
    <CANCEL>                     24       24       24       24
    <END OF MEDIUM>              25       25       25       25
    <SUBSTITUTE>                 26       63       63       63
    <ESCAPE>                     27       39       39       39
    <FILE SEPARATOR>             28       28       28       28
    <GROUP SEPARATOR>            29       29       29       29
    <RECORD SEPARATOR>           30       30       30       30
    <UNIT SEPARATOR>             31       31       31       31
    <SPACE>                      32       64       64       64
    !                            33       90       90       90
    "                            34       127      127      127
    #                            35       123      123      123
    $                            36       91       91       91
    %                            37       108      108      108
    &                            38       80       80       80
    '                            39       125      125      125
    (                            40       77       77       77
    )                            41       93       93       93
    *                            42       92       92       92
    +                            43       78       78       78
    ,                            44       107      107      107
    -                            45       96       96       96
    .                            46       75       75       75
    /                            47       97       97       97
    0                            48       240      240      240
    1                            49       241      241      241
    2                            50       242      242      242
    3                            51       243      243      243
    4                            52       244      244      244
    5                            53       245      245      245
    6                            54       246      246      246
    7                            55       247      247      247
    8                            56       248      248      248
    9                            57       249      249      249
    :                            58       122      122      122
    ;                            59       94       94       94
    <                            60       76       76       76
    =                            61       126      126      126
    >                            62       110      110      110
    ?                            63       111      111      111
    @                            64       124      124      124
    A                            65       193      193      193
    B                            66       194      194      194
    C                            67       195      195      195
    D                            68       196      196      196
    E                            69       197      197      197
    F                            70       198      198      198
    G                            71       199      199      199
    H                            72       200      200      200
    I                            73       201      201      201
    J                            74       209      209      209
    K                            75       210      210      210
    L                            76       211      211      211
    M                            77       212      212      212
    N                            78       213      213      213
    O                            79       214      214      214
    P                            80       215      215      215
    Q                            81       216      216      216
    R                            82       217      217      217
    S                            83       226      226      226
    T                            84       227      227      227
    U                            85       228      228      228
    V                            86       229      229      229
    W                            87       230      230      230
    X                            88       231      231      231
    Y                            89       232      232      232
    Z                            90       233      233      233
    [                            91       186      173      187 *** ###
    \                            92       224      224      188 ### 
    ]                            93       187      189      189 ***
    ^                            94       176      95       106 *** ###
    _                            95       109      109      109
    `                            96       121      121      74  ###
    a                            97       129      129      129
    b                            98       130      130      130
    c                            99       131      131      131
    d                            100      132      132      132
    e                            101      133      133      133
    f                            102      134      134      134
    g                            103      135      135      135
    h                            104      136      136      136
    i                            105      137      137      137
    j                            106      145      145      145
    k                            107      146      146      146
    l                            108      147      147      147
    m                            109      148      148      148
    n                            110      149      149      149
    o                            111      150      150      150
    p                            112      151      151      151
    q                            113      152      152      152
    r                            114      153      153      153
    s                            115      162      162      162
    t                            116      163      163      163
    u                            117      164      164      164
    v                            118      165      165      165
    w                            119      166      166      166
    x                            120      167      167      167
    y                            121      168      168      168
    z                            122      169      169      169
    {                            123      192      192      251 ###
    |                            124      79       79       79
    }                            125      208      208      253 ###
    ~                            126      161      161      255 ###
    <DELETE>                     127      7        7        7
    <C1 0>                       128      32       32       32
    <C1 1>                       129      33       33       33
    <C1 2>                       130      34       34       34
    <C1 3>                       131      35       35       35
    <C1 4>                       132      36       36       36
    <C1 5>                       133      21       37       37  ***
    <C1 6>                       134      6        6        6
    <C1 7>                       135      23       23       23
    <C1 8>                       136      40       40       40
    <C1 9>                       137      41       41       41
    <C1 10>                      138      42       42       42
    <C1 11>                      139      43       43       43
    <C1 12>                      140      44       44       44
    <C1 13>                      141      9        9        9
    <C1 14>                      142      10       10       10
    <C1 15>                      143      27       27       27
    <C1 16>                      144      48       48       48
    <C1 17>                      145      49       49       49
    <C1 18>                      146      26       26       26
    <C1 19>                      147      51       51       51
    <C1 20>                      148      52       52       52
    <C1 21>                      149      53       53       53
    <C1 22>                      150      54       54       54
    <C1 23>                      151      8        8        8
    <C1 24>                      152      56       56       56
    <C1 25>                      153      57       57       57
    <C1 26>                      154      58       58       58
    <C1 27>                      155      59       59       59
    <C1 28>                      156      4        4        4
    <C1 29>                      157      20       20       20
    <C1 30>                      158      62       62       62
    <C1 31>                      159      255      255      95  ###
    <NON-BREAKING SPACE>         160      65       65       65
    <INVERTED EXCLAMATION MARK>  161      170      170      170
    <CENT SIGN>                  162      74       74       176 ###
    <POUND SIGN>                 163      177      177      177
    <CURRENCY SIGN>              164      159      159      159
    <YEN SIGN>                   165      178      178      178
    <BROKEN BAR>                 166      106      106      208 ###
    <SECTION SIGN>               167      181      181      181
    <DIAERESIS>                  168      189      187      121 *** ###
    <COPYRIGHT SIGN>             169      180      180      180
    <FEMININE ORDINAL INDICATOR> 170      154      154      154
    <LEFT POINTING GUILLEMET>    171      138      138      138
    <NOT SIGN>                   172      95       176      186 *** ###       
    <SOFT HYPHEN>                173      202      202      202
    <REGISTERED TRADE MARK SIGN> 174      175      175      175
    <MACRON>                     175      188      188      161 ###
    <DEGREE SIGN>                176      144      144      144
    <PLUS-OR-MINUS SIGN>         177      143      143      143
    <SUPERSCRIPT TWO>            178      234      234      234
    <SUPERSCRIPT THREE>          179      250      250      250
    <ACUTE ACCENT>               180      190      190      190
    <MICRO SIGN>                 181      160      160      160
    <PARAGRAPH SIGN>             182      182      182      182
    <MIDDLE DOT>                 183      179      179      179
    <CEDILLA>                    184      157      157      157
    <SUPERSCRIPT ONE>            185      218      218      218
    <MASC. ORDINAL INDICATOR>    186      155      155      155
    <RIGHT POINTING GUILLEMET>   187      139      139      139
    <FRACTION ONE QUARTER>       188      183      183      183
    <FRACTION ONE HALF>          189      184      184      184
    <FRACTION THREE QUARTERS>    190      185      185      185
    <INVERTED QUESTION MARK>     191      171      171      171
    <A WITH GRAVE>               192      100      100      100
    <A WITH ACUTE>               193      101      101      101
    <A WITH CIRCUMFLEX>          194      98       98       98
    <A WITH TILDE>               195      102      102      102
    <A WITH DIAERESIS>           196      99       99       99
    <A WITH RING ABOVE>          197      103      103      103
    <CAPITAL LIGATURE AE>        198      158      158      158
    <C WITH CEDILLA>             199      104      104      104
    <E WITH GRAVE>               200      116      116      116
    <E WITH ACUTE>               201      113      113      113
    <E WITH CIRCUMFLEX>          202      114      114      114
    <E WITH DIAERESIS>           203      115      115      115
    <I WITH GRAVE>               204      120      120      120
    <I WITH ACUTE>               205      117      117      117
    <I WITH CIRCUMFLEX>          206      118      118      118
    <I WITH DIAERESIS>           207      119      119      119
    <CAPITAL LETTER ETH>         208      172      172      172
    <N WITH TILDE>               209      105      105      105
    <O WITH GRAVE>               210      237      237      237
    <O WITH ACUTE>               211      238      238      238
    <O WITH CIRCUMFLEX>          212      235      235      235
    <O WITH TILDE>               213      239      239      239
    <O WITH DIAERESIS>           214      236      236      236
    <MULTIPLICATION SIGN>        215      191      191      191
    <O WITH STROKE>              216      128      128      128
    <U WITH GRAVE>               217      253      253      224 ###
    <U WITH ACUTE>               218      254      254      254
    <U WITH CIRCUMFLEX>          219      251      251      221 ###
    <U WITH DIAERESIS>           220      252      252      252
    <Y WITH ACUTE>               221      173      186      173 *** ###
    <CAPITAL LETTER THORN>       222      174      174      174
    <SMALL LETTER SHARP S>       223      89       89       89
    <a WITH GRAVE>               224      68       68       68
    <a WITH ACUTE>               225      69       69       69
    <a WITH CIRCUMFLEX>          226      66       66       66
    <a WITH TILDE>               227      70       70       70
    <a WITH DIAERESIS>           228      67       67       67
    <a WITH RING ABOVE>          229      71       71       71
    <SMALL LIGATURE ae>          230      156      156      156
    <c WITH CEDILLA>             231      72       72       72
    <e WITH GRAVE>               232      84       84       84
    <e WITH ACUTE>               233      81       81       81
    <e WITH CIRCUMFLEX>          234      82       82       82
    <e WITH DIAERESIS>           235      83       83       83
    <i WITH GRAVE>               236      88       88       88
    <i WITH ACUTE>               237      85       85       85
    <i WITH CIRCUMFLEX>          238      86       86       86
    <i WITH DIAERESIS>           239      87       87       87
    <SMALL LETTER eth>           240      140      140      140
    <n WITH TILDE>               241      73       73       73
    <o WITH GRAVE>               242      205      205      205
    <o WITH ACUTE>               243      206      206      206
    <o WITH CIRCUMFLEX>          244      203      203      203
    <o WITH TILDE>               245      207      207      207
    <o WITH DIAERESIS>           246      204      204      204
    <DIVISION SIGN>              247      225      225      225
    <o WITH STROKE>              248      112      112      112
    <u WITH GRAVE>               249      221      221      192 ###
    <u WITH ACUTE>               250      222      222      222
    <u WITH CIRCUMFLEX>          251      219      219      219
    <u WITH DIAERESIS>           252      220      220      220
    <y WITH ACUTE>               253      141      141      141
    <SMALL LETTER thorn>         254      142      142      142
    <y WITH DIAERESIS>           255      223      223      223

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 2

=back

    perl -ne 'if(/.{33}\d{1,3}\s{6,8}\d{1,3}\s{6,8}\d{1,3}\s{6,8}\s{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 3

=back

    perl -ne 'if(/.{33}\d{1,3}\s{6,8}\d{1,3}\s{6,8}\d{1,3}\s{6,8}\s{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 4

=back

    perl -ne 'if(/.{33}\d{1,3}\s{6,8}\d{1,3}\s{6,8}\d{1,3}\s{6,8}\s{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);

"\t" is a <HORIZONTAL TABULATION>.  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

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 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;
    $ebcdic_string = tr/\000-\377/$cp_037/;

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

    my $ascii_string = $ebcdic_string;
    $ascii_string = tr/$code_page_chrs/\000-\037/;

XPG4 interoperability 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 see the iconv(1) man page.  One way to invoke the iconv 
shell utility from within perl would be to:

    $ascii_data = `echo '$ebcdic_data'| iconv -f IBM-1047 -t ISO8859-1`

or the inverse map:

    $ebcdic_data = `echo '$ascii_data'| iconv -f ISO8859-1 -t IBM-1047`

XXX iconv under qsh on OS/400?
XXX iconv on VM?
XXX iconv on BS2k? 

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

=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. (chr(0) eq "\c@"), 
(chr(1) eq "\cA"), and so on.  Perl on EBCDIC machines has been 
ported to take "\c@" -> chr(0) and "\cA" -> 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 substitions 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 "\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 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 <o WITH CIRCUMFLEX> 
that lie between I and J would not be matched by C</[H-K]/>.  
If you do want to match such 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 <o WITH CIRCUMFLEX>.

Another place 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 codepoints.
However, we may actually be concerned with characters rather than codepoints 
and on an EBCDIC machine would like 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 =~ /[ ¡¢£¤¥¦§¨©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 machine the
two letter abbreviation for a physician comes before the two letter
for drive, that is:

    @sorted = sort(qw(Dr. dr.));  # @sorted holds qw(Dr. dr.) on ASCII,
                                  # qw(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 WITH DIAERESIS> (203) comes before
<e WITH DIAERESIS> (235) on and 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 <SMALL LETTER SHARP S> is 
simply "SS" and that the upper case version of <y WITH DIAERESIS> 
is not in the 0..255 range but it is at U+x0178 in Unicode).

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 MONOCASE then sort data.

In order to minimize the expense of monocasing 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]/; 
XXX

This strategy does not preserve the case of the data and may not be
acceptable.

=head2 Convert, sort data, then reconvert.

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 URL ENCODING and DECODING

Note that some URLs have hexadecimal ASCII codepoints in them in an
attempt to overcome character 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 codepoint 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;

=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

Double byte EBCDIC code pages (?) XXX.

UTF-8, UTF-EBCDIC, (?) XXX.

=head1 OS ISSUES

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

=head2 OS/400 

=over 8

=item IFS access

XXX.

=back

=head2 OS/390 

=over 8

=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 locales

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

=back

=head2 VM/ESA?

XXX.

=head2 POSIX-BC?

XXX.

=head1 REFERENCES

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

L<perllocale>.

http://www.unicode.org/

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

B<The Unicode Standard Version 2.0> The Unicode Consortium, 
ISBN 0-201-48345-9, Addison Wesley Developers Press, July 1996. 

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.

=head1 AUTHOR

Peter Prymmer E<lt>pvhp@best.comE<gt> wrote this in 1999 and 2000 
with CCSID 0819 and 0037 help from Chris Leach and 
Andre' Pirard E<lt>A.Pirard@ulg.ac.beE<gt> as well as POSIX-BC 
help from Thomas Dorner E<lt>Thomas.Dorner@start.deE<gt>.
Thanks also to Philip Newton and Vickie Cooper.  Trademarks, registered 
trademarks, service marks and registered service marks used in this 
document are the property of their respective owners.