Executables

An executable is a file that contains a program configured to be run directly by a computer's operating system. When invoked, the operating system loads the file into memory and transfers control to the program's entry point. Executables are distinguished from data files and libraries, which are not intended to be run on their own.

Common executable formats vary by platform. Windows uses PE/COFF files, Linux and many Unix-like systems use ELF, and macOS uses Mach-O. Some environments support scripts that are interpreted rather than executed as native machine code; these are usually plain text files with a shebang or metadata and require an interpreter.

A typical executable contains a header with metadata such as architecture, entry point, and segment layout, followed by code, data, and resource sections. Executables may be statically linked, containing all libraries within the file, or dynamically linked, referencing shared libraries at runtime. Position-independent code and address space layout randomization are common protections in modern systems.

During loading, an operating system's loader maps the executable into memory, resolves dependencies, applies relocations, and sets memory protections before transferring control to the entry point. On modern systems, executables may be compressed, signed, or encrypted for security and integrity.

Security and distribution: modern systems use code signing and digital signatures to verify authenticity; antivirus scanners check executables; users obtain programs from trusted sources. Cross-platform development may target native executables for specific architectures or compile to portable bytecode run by a virtual machine or runtime.