A .COM file is an executable file format used primarily in DOS and early Windows operating systems. It's one of the simplest executable formats, typically limited to a maximum size of 64KB, including both code and data. Unlike more complex executable formats like .EXE, .COM files lack a header containing metadata about the program's structure. Instead, the operating system loads the entire file into memory and begins execution at the first byte. This simplicity made them quick to load and execute, but also imposed limitations on program size and complexity. They were commonly used for small utilities, games, and system commands. While less common in modern operating systems, .COM files can still be executed in compatible environments or emulators. Due to their small size and direct execution, they were also sometimes used for malicious purposes, making them a potential security risk if obtained from untrusted sources. The lack of a header also means that the operating system relies on the file extension to identify it as an executable, making it important to maintain the correct extension.