Compact size, extensibility, and built-in security is provided by enclosing into a file's header custom specifications and preventing file execution without knowing these specifications. The format allows for defined sections, organizing preliminary pre-processing of data before operating system (OS) execution. A file header, including standard and user-defined sections, is created and read by delegated processing; forming an executable file's header with inclusive specifications using the abstract data syntax description language (ASN.1); encoding header with compression encoding rules (PER); and creating a separate header section of interfaces table for components. Program assembly output includes an executable file in machine and/or byte code with a dynamic extensible header encoded according to ASN.1 with PER. During execution, the OS reads the file header and determines available sections, including links to external components and their interfaces, sections with machine/byte code, including user-defined sections, and links to delegate-processes for user sections data preparation.