====== Input Message File Format ======

The input message file is a standard ASCII file containing three types of lines:

  * Comment lines
  * Component identifier line
  * Component message lines

===== Comment Lines =====

Comments may appear anywhere in the file **except** between the component identifier line and the first message line.  
A comment line must begin with a semicolon ('';'') in the first column.

Example:
<code>
; This is a sample of an input
; message file for component DOS
; starting with three comment lines.
</code>

===== Component Identifier Line =====

A single line holding the three‑character component identifier. This identifier is prefixed to all message numbers.

In the example, the identifier is ''DOS''.

===== Component Message Lines =====

Each message line consists of a **message header** followed by the ASCII text of the message.

==== Message Header ====

The header is composed of the following fields, written contiguously:

  - Three‑character component identifier (e.g., ''DOS'').
  - Four‑digit message number (e.g., ''0100'').
  - A single character indicating the message type (see table below).
  - A colon (':').
  - A single blank space separating the header from the message text.

**Format:** ''COMPNNNNT: message text''

==== Message Types ====

^ Code ^ Type        ^ Meaning                                      ^
| E    | Error       | Error message                                |
| H    | Help        | Help text                                    |
| I    | Information | Informational message                        |
| P    | Prompt      | Prompt (user input expected)                 |
| W    | Warning     | Warning message                              |
| ?    | (unused)    | Placeholder for a number with no message text |

==== Numbering and Placeholder Entries ====

  * Message numbers may start at any value, but **must appear in strictly ascending sequential order** in the file.
  * When a particular number is not used, a placeholder entry is required. A placeholder consists of the full header with the type ''?'' and **no message text** after the colon and blank.  

Example: ''MAB0101?:''

===== Special Characters in the Message Text =====

The percent sign (''%'') has special meaning when used inside message text.

==== Suppressing the Trailing Newline (''%0'') ====

If the sequence ''%0'' appears as the very last characters of a message text, the ''DosGetMessage'' API will **not** append a carriage return and line feed (CR+LF). This is typically used for prompts so that user input can follow on the same line.  

==== Inserting Variable Strings (''%1'' – ''%9'') ====

Sequences ''%1'' through ''%9'' mark positions where variable strings are inserted at runtime. The actual values are provided via the ''Itable'' and ''IvCount'' parameters of the ''DosGetMessage'' call.

Example: the message ''%1 files copied'' will have ''%1'' replaced by an appropriate string (e.g., a number of files).

===== Complete Input File Example =====

<code>
; This is a sample of an input
; message file for component MAB
; starting with three comment lines.
MAB
MAB0100E: File not found
MAB0101?:
MAB0102H: Usage: del [drive:][path] filename
MAB0103?:
MAB0104I: %1 files copied
MAB0105W: Warning! All data will be destroyed!
MAB0106?:
MAB0107?:
MAB0108P: Do you wish to apply these patches (Y or N)? %0
MAB0109E: Divide overflow
</code>

  * ''MAB'' – component identifier.
  * ''MAB0100E'' – error message.
  * ''MAB0101?'' – placeholder for an unused number.
  * ''MAB0104I'' – informational message with variable insertion (''%1'').
  * ''MAB0108P'' – prompt with ''%0'' to suppress the trailing newline.