File Extension WPJ File Format Watcom C/C++ Project WPJ stands for Watcom C/C++ Project. This was last updated in March 2012 By Margaret Rouse Browse File Extensions Alphabetically: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # Ask a Question. Find an Answer. Ask your peers a question about this file extension. Ask a Question Using DOS extenders on NT-kernel-based OSes RPGLE program to check data across 3 file systems Help with embedded SQL in RPG. Dang thing hates the delete statement?