In the early days of computing, mainframe users accessed their systems using a dumb terminal. Dumb terminals are input/output devices with no processing capability and only enough memory to decipher particular control codes. Dumb terminals were most commonly found in large organizations with the need to process immense numbers of data transactions, such as financial institutions. For organizations like these, the processing power of the mainframe was necessary in order to successfully accomplish basic daily operations.

With the advent of PC's, users needed a way to interact with their organization's mainframe from their desktops. Terminal emulators were developed to fill this need. Using terminal emulation software installed on the PC means that only one machine is needed to access the mainframe. Terminal emulators not only eliminate the need for a dumb terminal, they also provide additional features that serve to extend capabilities and increase productivity.

Dumb terminals use a standard set of codes to communicate with the host system. These codes, also known as escape sequences, are responsible for performing basic screen display functions such as changing colors and moving the cursor. In the days when the use of dumb terminals was common, different terminal manufacturers used different sets of standard codes. The most common terminal types are 3270, 5250, VT, and SCO ANSI terminals. Many large organizations use more than one terminal type. In most cases, one terminal emulator can be used to access a combination of terminal types, eliminating the need for multiple dumb terminals.

Most modern day terminal emulators use a graphical interface that is similar to the user's existing PC applications. This makes using a terminal emulator more user friendly than a dumb terminal, and decreases the learning curve associated with host access - especially for new users. In large organizations where employee turnover is a concern, this reduction in training time can have a significant impact on the company's bottom line.

Unlike dumb terminals, PC's are capable of processing data. When combined with a terminal emulator, this ability allows PC users to perform tasks that simply weren't possible with dumb terminals alone. For example, with a terminal emulator, users can print host data to local and network printers or to files on their PC. Data being sent to and from the host can also be processed automatically.

Scripting can be used in conjunction with the terminal emulator to automate routine tasks. More advanced terminal emulators like Zephyr's PASSPORT provide the ability to assign these scripts, typically referred to as macros, to a key on the keyboard, a keypad button, toolbar button or the mouse. One example of a time-saving macro is a script that can be configured to automatically run when the host session is established and dynamically enter the user's logon details.

Contemporary terminal emulators may also include SSL or SSH security to encrypt transactions between the PC and the mainframe. Server authentication and encryption provides secure data access across TCP/IP networks. With the security of SSL or SSH, terminal emulation sessions are protected from eavesdropping, tampering, or message forgery over TCP/IP. This feature can be critical for those organizations that use remote access across the Internet to retrieve sensitive data on corporate mainframes.

Although mainframe technology is decades old, it is still in use in countless organizations today. These organizations now use terminal emulators instead of dumb terminals to access these systems. BMC Software recently conducted a survey of 1,100 IT managers whose organizations use mainframes. 95% of the respondents indicated that the mainframe still plays a critical role in their IT infrastructure, and will continue to do so.