Terminals were originally categorized as interactive or remote batch, the latter also commonly referred to as a remote job entry device. An interactive terminal is typically used to transmit relatively short queries or to provide an operator with the ability to respond to computer-generated screen displays by entering data into defined fields prior to transmitting the filled in screen.
Once the data have been received, the destination device will respond to the transmission in a relatively short period of time, typically measured in seconds. In comparison, remote batch terminals provide the operator with the ability to group or batch a series of jobs that can range in scope from programs developed for execution on a large computer to queries that are also structured for execution against a database maintained on a large computer system.
The introduction of the personal computer altered the previous distinction. That is, the ability to use the hard drive of a PC as a storage mechanism enables the personal computer to transmit and receive files that can range up to a gigabyte or more in size.
Although the distinction between interactive and batch terminals was essentially eliminated by the PC, it is an important topic to note as many software programs were developed to turn a personal computer into a specific type of terminal by emulating the features of a terminal. As you might expect, such software is referred to as terminal emulation software.
Interactive terminal classification
One method commonly used to classify interactive terminals is based on their. This method of terminal classification has its origins with tletype terminals in which those terminals could be configured as a receive only (RO), keyboard send–receive (KSR) or automatic send–receive (ASR) device.
Receive only (RO)
A receive only (RO) terminal consists of a stand-alone printer with a serial communications interface but lacking a keyboard. Originally developed to simply receive messages transmitted on message switching systems developed in the 1930s, a limited number of RO terminals are still in use today.
Keyboard send-receive (KSR)
Originally, keyboard send–receive (KSR) terminals included a printer, serial communications interface, and keyboard. This permitted the terminal operator to both originate a message from the keyboard as well as to print a received message.
Automatic send-receive (ASR)
The third interactive terminal classification is automatic send–receive (ASR). An ASR terminal consists of a printer, serial communications interface, keyboard and auxiliary storage. Here the auxiliary storage permits messages to be composed ‘off-line’ with the terminal not attached via a communications facility to its intended transmission destination.
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