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README.MD

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+# COUNTRY.SYS
+
+## Description:
+
+     FreeDOS COUNTRY.SYS - International Localization Data
+
+     This file contains country-specific localization data for FreeDOS,
+     including date/time/currency formats, uppercase/lowercase mappings,
+     collating sequences (sorting orders), filename character tables,
+     and yes/no prompt characters for multiple country and codepage
+     combinations.
+
+     COUNTRY.SYS provides the data that is returned by DOS API calls: 
+     INT21h/38h, INT21h/6501h-6507h and INT2Fh/1400h-14FFh
+
+## Purpose:
+
+     COUNTRY.SYS provides international support for DOS applications by
+     defining locale-specific behavior. It is loaded by the kernel at
+     boot time via CONFIG.SYS: COUNTRY=<code>,<codepage>,<filepath>
+
+## Compatibility:
+
+     This file is binary-compatible with COUNTRY.SYS from:
+     - MS-DOS (Microsoft DOS)
+     - PC-DOS (IBM DOS)
+     - PTS-DOS
+     - OS/2 *** 
+     - Windows 9x
+
+  *** COUNTRY.SYS format is largely unchanged since MS-DOS 3.x
+  The YESNO tables are unused except in FreeDOS and OS/2 (W95 unknown),
+  However, unlike the OS/2 one, FreeDOS only provides 1st character as an 
+  ASCIIZ string, "Y" or "N", while OS/2 provides full words "YES" or "NO".
+  It is unknown if Windows 95 uses this and if it is in a compatible format.
+
+## Basic Usage:
+
+    Add a COUNTRY= entry in CONFIG.SYS which refers to the COUNTRY.SYS file.
+        COUNTRY=<country #>,<codepage #>,C:\DOS\COUNTRY.SYS
+
+    For example, United States (1) with codepage 850:
+        COUNTRY=1,850,C:\DOS\COUNTRY.SYS
+
+## File Format:
+
+     Format described in Ralf Brown's Interrupt List (RBIL)
+     Tables 2619-2622
+
+## Structure Overview:
+
+     1. File Header       - Magic signature and entry count
+     2. Entry Table       - Index of all country/codepage combinations
+     3. Subfunction Data  - Actual localization data for each country:
+        a. Country Info   - Date/time/currency format (subfunction 1)
+        b. Uppercase      - Character case mapping (subfunction 2)
+        c. Lowercase      - Inverse case mapping (subfunction 3)
+        d. Filename Upper - Filename character mapping (subfunction 4)
+        e. Filename Chars - Valid filename characters (subfunction 5)
+        f. Collating Seq  - Sort order (subfunction 6)
+        g. DBCS Table     - Double-byte character sets (subfunction 7)
+        h. Yes/No Chars   - Prompt characters (subfunction 35)
+
+## Copyright Information:
+
+    Copyright 2004, The FreeDOS Project
+
+    COUNTRY.SYS is free software; you can redistribute it and/or
+    modify it under the terms of the GNU General Public License
+    as published by the Free Software Foundation; either
+    version 2, or (at your option) any later version.
+
+    It is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty
+    of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+    See the GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public
+    License along with FreeDOS; see the file COPYING.  If not,
+    write to the Free Software Foundation, Inc.,
+    59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+    or go to http://www.gnu.org/licenses/gpl.html
+
+## Credits:
+
+    * Created as a kernel table by:          Tom Ehlert
+    * Reformatted and commented by:          Bernd Blaauw
+    * Separated from the kernel by:          Luchezar Georgiev
+    * Case/collate tables added by:          Eduardo Casino
+    * Yes/No and codepage 850 table by:      Steffen Kaiser
+    * Amended by many contributors
+
+## REFERENCES
+
+    See Matthias Paul's extensive COUNTRY.SYS documentation file: COUNTRY.LST
+
+    ### Standards used in this file:
+
+    - ISO 3166-1: Country codes
+      https://www.iso.org/iso-3166-country-codes.html
+    - ISO 639-1: Language codes
+      https://www.loc.gov/standards/iso639-2/php/code_list.php
+    - ISO 4217: Currency codes
+      https://www.iso.org/iso-4217-currency-codes.html
+    - Ralf Brown's Interrupt List (RBIL): DOS structures
+      https://www.ctyme.com/rbrown.htm
+    - European Central Bank: Euro adoption dates
+      https://www.ecb.europa.eu/euro/intro/html/index.en.html