displayed at once. This allows the user to pause the display and read long messages that scroll through the screen too quickly to read, such as when the system is booting up (provided the keyboard driver has already been loaded). If not configured otherwise, and can be used instead of Scroll Lock in any terminal in Linux to freeze and unfreeze the terminal output respectively. This behavior emulates the Hold Screen key or similar flow control mechanisms on computer terminals. The behavior must be distinguished from pressing the Pause key during POST or under DOS, which, by default, has the effect of temporarily halting the running process. On the FreeBSD system console, the key additionally enables scrolling: after pressing Scroll Lock, one can use and to scroll up or down. Pressing Scroll Lock again disables this mode and moves back to the bottom of the output. The Linux console implements this behaviour by using and , not requiring to be active although ability to scroll in Linux console has been removed in 4.4.240 kernel update due to a vulnerability (CVE-2020-14390) and code not being maintained. Boot diagnostics In Multiuser DOS, System Manager, and REAL/32, activating during boot will always enter a special diagnostic mode, where the operating system and loaded device drivers will display detailed status and debugging information about themselves and their interaction with the operating system, sometimes up to several screenfulls per loaded driver. Automatic scrolling is suspended for as long as remains activated. DR-DOS 7.02 and higher provides a CONFIG.SYS directive named SCROLLOCK=ON|OFF to change the Scroll Lock status on the fly. Activating during boot will enter a DIAG mode as well, wherein some special drivers may display more verbose messages, but in contrast to the situation under the Multiuser DOS family normal DOS drivers do not typically display additional information. The operating system, however, will temporarily suspend any automatic timeouts (TIMEOUT=<seconds>,<character>,<switch>) in CONFIG.SYS trace (TRACE=ON|OFF) and / single-stepping modes for as long as is active. Debugging In the Microsoft Windows NT family starting with Windows 2000, a debugging feature can be enabled, that allows the user to manually crash the system, generating a memory dump for analysis of the current state of the operating system. This can be accomplished by setting the REG_DWORD registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\i8042prt\Parameters\CrashOnCtrlScroll to 1. Once set, the user can hold the key and tap the key twice to trigger a Blue Screen