ZTerm is a shareware terminal emulator for Apple Macintosh computer systems. It was introduced in 1992 running on Macintosh Operating System 7 and has been updated to run on the latest version of Mac OS X. Its name comes from its use of the Zmodem file transfer protocol, which ZTerm implemented in a particularly high-performance package. Contrary to the OS X built-in Terminal, which only communicates with other programs, ZTerm only communicates with hardware serial ports.
When it was first introduced, ZTerm was one of the highest performing terminal emulators on the Mac, both in terms of basic text display as well as file transfer performance. Its hardware support included carrier detect (CD), hardware hangup (DTR) and hardware flow control, as well as speeds up to 119,200 bit/s on those machines that supported it. These features were not universally supported in Mac hardware, so many emulators simply ignored them. Even if these speeds were offered, most Mac terminals of the era had trouble keeping up with faster modems, especially 9600 bit/s and faster.
ZTerm supported one of the widest variety of file transfer protocols available on the Mac, including a full implementation of ZModem, YModem, YModem-G, almost all of the common varieties of XModem with different packet sizes and error correction methods, and even the rare but useful B protocol for use on Compuserve. ZTerm also supported auto-starting transfers from ZModem and B, where commands from the host automatically triggered transfers from the client.
Additionally, ZTerm included a complete PC graphics character set and ANSI escape codes, including color. This made it one of the few terminals on the Mac that properly displayed ASCII art, and allowed full interaction with PC-based BBS systems that used these features extensively. ZTerm also allowed the mouse to be used to position the cursor, sending a stream of ANSI codes to move it to the clicked location.
By the time that Mac OS X was being released around 2002, the BBS world had largely disappeared. However, a number of devices (including some routers and lab equipment) still use serial ports to communicate, typically for diagnostic and debugging purposes.
On 19 April 2001 Alverson released version 1.1b4 that ran on OS X and Mac OS 8.6 and Mac OS 9 using Carbon. Later a "Classic" version was released that did not require Carbon, allowing it to run on older machines that could not support Mac OS 8 or Mac OS 9. On 18 July 2011 Alverson released a Universal Binary version 1.2 that runs on OS X 10.4 and later.
On modern machines without built-in serial ports, ZTerm can identify and use a wide variety of USB-based serial devices. The list of supported hardware includes the standard Macintosh serial ports and Geoport on pre-PowerPC G3 CPU PowerPC Macintosh computers, the built-in Apple internal modem slot and the USB ports on PowerPC G3, PowerPC G4, PowerPC G5 and Intel CPU Macintosh computers, and can be configured to work with adapters (including various USB port to serial port adaptors - such as those made by Keyspan, and Apple internal modem slot to serial port adaptors - like the Stealth Serial Port and the now discontinued Griffin Technology gPort, under OS X), giving it a unique use for BBSers and hardware tinkerers.