HP 2640
[7] All of these early members of the 2640 series had the relatively slow 8008 CPU running at 700 kHz, and they were thus limited to speeds of 2400 baud.
[10] In September 1976, HP introduced the 2645A, which could handle speeds up to 9600 baud and had a number of advanced features, including as an option the mini-tape cartridge storage of the 2644A.
[17] In October 1980, HP introduced the 2642A, which was like the 2645A, but instead of optional tape cartridges it had a standard 5.25-inch floppy disk drive storing 270 KB per diskette.
[18] The ultimate and final model in the 2640 series was the 2647F programmable graphics terminal introduced in June 1982, an improved replacement for the 2647A with the 2642A's floppy drive.
They never achieved the fame of the VT100 among programmers but included sophisticated features not found in the VT100, such as offline forms, multipages, and (in some models) local storage.
HP's response was to specify a cathode-ray tube with an aspect ratio designed around the desired character shape instead of the other way around.
The keyboard had flat tops, similar to the HP 9800 series desktop computers rather than the curved contours now considered to be ergonomic.
It featured three keypad areas: Alphabetic, numeric, and an array of cursor positioning and editing keys somewhat similar to modern PC keyboard layouts.
There were also a number of smaller function and feature control keys arrayed in two rows above the normal keypad areas.
Later models arranged these across the top row, and provided for screen labels close to their respective keys.
This arrangement is now common on TI graphic calculators, and automated teller and gas pump machines, though no longer used in GUI user interfaces.
For example, more memory (providing larger scrollback capability) could be easily added, the serial interface could be changed from RS-232 to current loop, etc.
It also supported teletype character mode like a standard ASCII terminal, and did not need specialized communications like IBM.
Software enhancements which did not affect the appearance such as dim or underline, but protected and unprotected fields were also coded with embedded bytes.
When the cost of memory came down by the 262X series, this was changed to a "parallel" structure with one bit for each enhancement code, but the logic required to emulate previous behaviors was complex.
This was possible in many terminals of the day, but the HP 2640 was smart enough to only retransmit the line from the first character typed by the user, omitting, for example, the operating system's command prompt.
Only the data within the unprotected areas would be transferred in this way, using a semi block mode mechanism, a sort of half way house between block mode and normal character mode, Formatted fields also meant forms could be stored in memory ( tested for and recalled locally or repainted from the host if not present), just the unprotected data areas need be sent, thereby removing the need to repaint or issue direct cursor placements in order to update the screen (TIM/3000 Air Call Computer Systems).
