PCBoard (PCB) was a bulletin board system (BBS) application first introduced for DOS in 1983 by Clark Development Company. Clark Development was founded by Fred Clark. PCBoard was one of the first commercial BBS packages for DOS systems, and was considered one of the "high end" packages during the rapid expansion of BBS systems in the early 1990s. Like many BBS companies, the rise of the Internet starting around 1994 led to serious downturns in fortunes, and Clark Development went bankrupt in 1997. Most PCB sales were of two-line licenses; additional line licenses (in ranges of 5, 10, 25, 50, 100, 250 and 1000) were also available. A native 32-bit IBM OS/2 version became also available with PCB V15.22 and higher. There were also a few tools available for PCBoard, which were specifically developed for the OS/2 2.0 and OS/2 Warp operating system. Multinode support PCBoard supported the 16C550 UARTs (universal asynchronous receiver transmitter), such as 16550 UART ("Fifo"), 16554 UART and 16650 UART, which made it possible to run multiple nodes of the BBS on a single (multitasking) computer using either using IBM OS/2 or the DOS multitasking tool DESQview in combination with the memory manager QEMM. Some sysops tried to run PCBoard on the (then) new Windows 95 operating system by Microsoft and reported mixed results. Stability was critical for a BBS, which was usually running 24/7, and the early version of the Microsoft 32-bit operating system lacked it. Windows 95 was never officially supported by CDC. Standard PCs then and today have only one or two (if any) serial ports (COM ports), which are needed to connect an external modem to a computer. This made multiport cards like the G-Tek "BlackBoard", "BBS550" or "SmartCard" and the "DigiCard" by Digi International popular among sysops. Other options were internal multi-modem cards and multiple computers connected by local area network. PCBoard also supports ISDN (Integrated Services Digital Network) and Telnet access via the Internet. The open source terminal emulator SyncTERM, available for Win32, Linux, FreeBSD, NetBSD, OpenBSD, Solaris and Mac OS X can be used for example to connect to the few remaining PCBoard BBS installations that are connected to the Internet. Multi-BBS networks Starting in 1988, the RelayNet, also known as RIME for RelayNet International Mail Exchange, allowed BBS's running PCBoard to join a network that exchanged messages with other BBS's in a system similar to the older FidoNet.