File extension
A file extension or file type is a part of the file specification that may identify the file structure (such as .TXT for text files or .C for C code) or sometimes the order in which the files should be used (backup savesets for VMSINSTAL have the extensions .A, .B, .C, etc.).
A file type must consist of no more than 39 alphanumeric characters and may include the dollar sign ($) and the underscore(_). Empty file types are also permitted.
Assigning file types in OpenVMS is arbitrary: there is no requirement as to what type a file should have other than if the non-default file type is used, the user will have to enter the file type when using the file.
Default file types
Certain OpenVMS commands and utilities have default file types that are assumed in the default file specification and therefore do not need to be specified: for example, TYPE defaults to .LIS files and @ defaults to .COM files.
Default file types used by DCL commands
| File type | Contents |
|---|---|
| .CLD | Command description file |
| .COM | Command procedure file |
| .DAT | Data file |
| .DIF | Output created by the DIFFERENCES command |
| .DIR | Directory file |
| .DIS | Distribution list file for the MAIL utility |
| .EDT | Startup command file for the EDT editor |
| .EXE | Executable program image file created by the linker |
| .HLB | Help text library file |
| .HLP | Input source file for help libraries |
| .INI | Initialization file |
| .JOU | Journal file created by the EDT editor |
| .LIS | Listing file created by a language compiler or assembler; default input file for the PRINT and TYPE commands |
| .LOG | Batch job output file |
| .MAI | Mail message file |
| .MEM | Output file created by DIGITAL Standard Runoff (DSR) |
| .PS | POSTSCRIPT format file |
| .REGIS | Regis format file |
| .RNO | Input source file for DIGITAL Standard Runoff (DSR) |
| .SIX | Sixel graphic file |
| .SYS | System image file |
| .TJL | Journal file created by the DECTPU and ACL editors |
| .TLB | Text library file |
| .TMP | Temporary file |
| .TPU | Command file for the EVE editor |
| .TPU$JOURNAL | Journal file created by the EVE editor |
| .TXT | Input file for text libraries or Mail utility output files |
Default file types for language source programs
| File type | Contents |
|---|---|
| .ADA | Input source file for the Compaq Ada compiler |
| .BAS | Input source file for the BASIC compiler |
| .B32 | Input source file for the VAX BLISS-32 compiler |
| .C | Input source file for the Compaq C compiler |
| .COB | Input source file for the VAX COBOL compiler on OpenVMS VAX systems and the Compaq COBOL compiler on OpenVMS Alpha systems |
| .FOR | Input source file for Compaq Fortran (Compaq Fortran for OpenVMS VAX systems was formerly VAX Fortran) |
| .M64 | Input source file for the MACRO-64 assembler for OpenVMS Alpha |
| .MAP | Memory allocation map created by the Linker utility |
| .MAR | Input source file for the VAX MACRO assembler or the MACRO-32 Compiler for OpenVMS Alpha |
| .MLB | Macro library for the MACRO assembler |
| .MSG | Source file that specifies the text of messages |
| .OBJ | Object file created by a language compiler or assembler |
| .OLB | Object module library |
| .OPT | Options file for input to the LINK command |
| .PAS | Input source file for the Pascal compiler |
| .PLI | Input source file for the PL/I compiler |
| .STB | Symbol table file created by the Linker utility |
| .UPD | Update file of changes for a VAX MACRO source program; also input to the SUMSLP utility |
