Bret Johnson developed DPMS-enabled Print Screen to file (PRTSCR) and USB drivers for DOS. In 1993, Helix Software Company's memory manager NETROOM 3 introduced a feature very similar to Novell's DPMS: CLOAKING was used to relocate Helix's and third-party drivers into extended memory and run them at ring 0. Providing its functions as an extension to the real-mode EMS and XMS interface, its protected mode services are available under INT 2Ch. A CLOAKING developer's kit was available which included a NuMega SoftICE debugger. Cloaked driver or TSR software hooking interrupts had to leave a small 11-byte stub in conventional memory which would invoke the CLOAKING server to pass execution to the protected mode portion of the driver software. CLOAKING includes support for seamless operation under Windows 3.x and Windows 95, providing compatible INT 2Ch services to protected mode drivers via a Windows VxD, as well as seamless debugging through Windows start-up using SoftICE. This ability to transition between protected mode host environments is also the subject of a patent. CLOAKING integrates into and works with existing virtual memory control programs, without switching descriptor tables or resetting the control registers. This allows for faster interrupt processing, according to Helix's documentation. In contrast to Novell's DPMS, Helix's CLOAKING driver can be loaded high, but it does not run on 286 machines, though it does support 16-bit services and program structure on a 386. Also, CLOAKING 2.01 has been found to be incompatible with the DR-DOS multitasker (). If no DPMS server is present when CLOAKING.EXE loads, CLOAKING will, by default, also provide a cloaked DPMS server at a mere 100 bytes increase of its DOS memory footprint. However, it can also coexist with a DPMS server loaded before CLOAKING. The loading of its built-in DPMS server can be suppressed using the parameter. DPMS-enabled drivers will work with both DPMS or CLOAKING, but not vice versa. In NETROOM v3.04, Supplemental Disk distribution dated "2-10-95," the password protected resource file NR.ZIP (679,271 KB) has an undocumented file; DPMSCLK.EXE (13,904 KB), "Cloaked DPMS Server v3.03". The file does not reveal support for any options or parameters when queried using the standard help option, .