autoexecbat

Autoexec.bat, commonly written as autoexec.bat or autoexecbat, is a legacy batch file used by DOS and early Windows to automate startup tasks. When a DOS session starts, the command interpreter reads autoexec.bat and executes the commands in order. In Windows 95/98/ME, the file was loaded during system startup to configure the environment and initialize hardware or software components.

In modern Windows (NT-based systems such as Windows XP and later), autoexec.bat no longer runs at system startup. It may still be used within a DOS compatibility environment, such as NTVDM for 16-bit applications, or inside DOS emulators like DOSBox. The 16-bit DOS startup scripts for Windows NT are autoexec.nt and config.nt, which serve similar roles within the Windows subsystem. Today, autoexec.bat is mainly a relic for compatibility or for users running legacy software.

Common contents include environment variable definitions (SET PATH=...), device initialization commands, or program launches. The first line is often @echo off to suppress command output. Comments typically use REM or ::. Because it runs automatically, the file can influence the startup environment or program behavior; errors can prevent a session from starting correctly. It is a plain text file and can be edited with any text editor.

Security and maintenance: Because commands execute on startup, tampering with autoexec.bat could alter system behavior or pose security risks. Only trusted sources should edit it, and backups are advised. In modern systems, editing autoexec.bat is usually unnecessary unless supporting legacy software or specific emulation environments.