COFF

COFF (Common Object File Format) is a widely used file format for executable, object code, and shared library files. It was originally developed by Unix System Laboratories (USL) and has since become a standard format for many operating systems, including Unix, Linux, and Windows.

Overview

COFF is designed to store various types of data related to executable and object code files. It provides a structured format that allows for efficient storage and retrieval of information. COFF files typically contain sections that store code, data, and other related information.

History

The development of COFF can be traced back to the early days of Unix. In the late 1980s, USL introduced COFF as a replacement for the older a.out format. COFF offered several advantages over its predecessor, including support for multiple sections, improved debugging capabilities, and better compatibility with different architectures.

Structure

A COFF file consists of several sections, each serving a specific purpose. The most common sections found in a COFF file include:

1. Text Section: This section contains the executable code of the program or library.

2. Data Section: This section stores initialized data, such as global variables and constants.

3. BSS Section: This section is used for uninitialized data. It reserves space for variables that will be initialized at runtime.

4. Symbol Table: The symbol table contains information about the symbols defined and used in the file. Symbols can include functions, variables, and other program elements.

5. Relocation Table: This table provides information about the locations in the code or data sections that need to be modified during the linking process.

Usage

COFF files are used in various stages of the software development process. During compilation, the compiler generates COFF object files that contain the compiled code and related information. These object files are then linked together to create the final executable or shared library.

COFF files are also used for debugging purposes. Debuggers can read the symbol and relocation tables in a COFF file to provide information about the program's execution and aid in troubleshooting.

Related Formats

COFF has influenced the development of other file formats, such as the Portable Executable (PE) format used by Windows. PE is an extension of COFF and includes additional features specific to the Windows operating system.

See Also

• Executable file format
• Object file format
• Portable Executable