Hi, I need to add an header in txt format to a bynary file produced in OpenVms .. how it can be made ?

There is nothing specific for VMS in this question, it is more general programming. For existing files: put the header text in a new file, then append the "binary" file. (with DCL command APPEND). Depending on the file/record format of the binary file, this may or may not work. Eventually You have to create the header file with the specific FDL of the "binary" file (CREATE/FDL=fdlfile, the fdlfile is the output of ANALYZE/RMS/FDL of the existing 'binary" file). But as always: what do You want to achive ? All depends on the application which wants to use the file(s). Do they expect to have the text at the beginning ? There is no general meaning of a "binary" file. The programming language of the application usually defines file/record structures.