Description of the statements

• ADD-DOCUMENTATION - Add documentation lines
• ADD-MSG - Add message unit
• COPY - Copy message unit
• DELETE-DOCUMENTATION - Delete documentation lines
• DELETE-MSG - Delete message unit
• END - Terminate MSGMAKER
• MERGE-MSG-FILES - Merge message files
• MODIFY-DOCUMENTATION - Modify and delete documentation lines
• MODIFY-MSG - Modify message unit
• MODIFY-OPTION - Overwrite message unit
• MOVE - Copy and delete message unit
• OPEN-MSG-FILE - Open message file
• SHOW - Display message file contents