Online is when a computer is connected via the modem and telephone lines to another computer. Protocol refers to the complete structure of the the information that is going to from one modem to the other. Data speed in bits per second, parity, the number of start bits, the number of data bits, and the number of stop bits all constitute the protocol. The same settings must be used in both computer modems. Stop bits are every character of information that go through a modem and is preceded by one or more stop bits.
Most common telecommunications sytems use one stop bit.
Communications software has a menu selection to set the number of stop bits. Telecommunications software is a program used to allow the computer to communicate through a modem. Most software of this type dials the requested number and sets the modem for the system that is being called. Terminal emulation - most mainframe computers are designed to communicate with specific workstations called terminals. For a microcomputer to communicate with a mainframe, the microcomputer telecommunications sotware must be able to perform like, or emulate, an appropriate terminal.