**Client Server Runtime Subsystem**, or csrss.exe, is a component of the [[Windows NT]] family of operating systems that provides the user mode side of the [[Win32 subsystem]] and is included in [[Windows NT]] 3.1 and later. Because most of the [[Win32 subsystem]] operations have been moved to kernel mode drivers in [[Windows NT]] 4 and later, **CSRSS** is mainly responsible for [[Win32]] console handling and GUI shutdown. It is critical to system operation; therefore, terminating this process will result in system failure. Under normal circumstances, **CSRSS** cannot be terminated with the taskkill command or with Windows **Task Manager**, although it is possible in [[Windows Vista]] if the Task Manager is run in **Administrator** mode. On [[Windows 7]] and later, Task Manager will inform the user that terminating the process may result in system failure, and prompt if they want to continue. In [[Windows NT]] 4.0 however, terminating **CSRSS** without the Session Manager Subsystem ([[SMSS]]) watching will not crash the system. However, in [[Windows XP]], terminating **CSRSS** without [[SMSS]] watching will crash the system due to the critical bit being set in RAM for **csrss.exe**.

====== History ======

The [[Windows NT]] 3.x series of releases had placed the Graphics Device Interface component in **CSRSS**, but this was moved into kernel mode with [[Windows NT]] 4.0 to improve graphics performance. The Windows startup process from [[Windows Vista|Vista]] onward has changed significantly. Two instances of csrss.exe are running in [[Windows 7]] and [[Windows Vista]].