Editing VMU (section)

==Hardware==
[[File:Sega-Dreamcast-Cont-n-VMU.jpg|thumb|right|VMUs attach through either of two slots on the controller; the screen of the VMU attached in the front slot is visible through a window on the controller.]]
[[File:Sega-Dreamcast-Controller-wVMU-FL.jpg|thumb|right|The VMU shown inside the controller]]
For use as a memory card and second screen, the VMU is plugged directly into one of two slots on a Dreamcast controller (up to two VMUs may be plugged in each controller, and eight VMUs per Dreamcast console).

Upon initial use, the player is prompted to set the date and time, and then select from a group of bitmap images to serve as the default background for the VMU (various Dreamcast titles may offer players additional background images for the unit). This image is displayed while the Dreamcast console is in the operating system menu.

When operated independently of the Dreamcast console, the VMU acts as a file manager, clock/calendar (with selectable clock animations), and handheld game console. VMUs may also connect to each other directly to facilitate file transfer or [[multiplayer gaming]].

The VMU runs on two [[CR2032 battery|CR-2032]] [[lithium battery|lithium batteries]] which are inserted into the rear of the VMU under a screw-secured lid. Without battery power, the VMU still functions as a memory card and auxiliary display, but cannot play downloaded mini-games. Additionally, a VMU without battery power will beep when the Dreamcast is powered on (if the VMU is inserted into a connected Dreamcast controller)

The VMU has 128 [[kilobyte|KB]] of flash memory, but by default 28 KB is reserved for system use leaving 100 KB for data storage, which is divided into 200 'blocks' – one block equaling 512 bytes. In recent years, homebrew programs like Dream Explorer (aka VMU Tool) have allowed users to unlock an extra 44 blocks (22 KB) of this reserved space<ref>{{cite web | title=Dream Explorer | url=http://bswirl.kitsunet.org/vmutool/release/about/?lg=en&menu= | access-date=May 31, 2009 | archive-date=October 7, 2011 | archive-url=https://web.archive.org/web/20111007145443/http://bswirl.kitsunet.org/vmutool/release/about/?lg=en&menu= | url-status=dead }}</ref> increasing the overall VMU capacity to 244 blocks. However, a handful of games might be unable to detect the memory card if this is done, although none have been reported apart from DreamKey/DreamPassport and [[Metropolis Street Racer]].{{Citation needed|date=August 2023}}