From HandWiki
Short description: Early video display terminal
Terminal with keypad
ManufacturerLear Siegler
TypeComputer terminal
Release date1976 (1976)
Introductory priceUS$995 (equivalent to $4,500 in 2019)

The ADM-3A was an influential early video display terminal, introduced in 1976.[1] It was manufactured by Lear Siegler and had a 12-inch screen displaying 12 or 24 lines of 80 characters. It set a new industry low single unit price of $995.[lower-alpha 1] Its "dumb terminal" nickname came from some of the original trade publication advertisements.[2] It quickly became commercially successful because of the rapid increase of computer communications speeds, and because of new minicomputer and microcomputer systems released to the market which required inexpensive operator consoles.


Lear Siegler, Inc. (LSI) manufactured its first video display terminal in 1972 – the 7700A.

In 1973, LSI hired a new head of engineering, Jim Placak. He and his team created the ADM-1 later that year. It set a new pricing low in the industry at $1,500.[lower-alpha 2] Its lower cost was primarily due to a unique single printed circuit board design. In early 1973 the LSI division in Anaheim, California that manufactured these and other products hired a management team for this product line – a VP, national sales manager, and one regional sales manager – for the western region. The ADM-1 was followed by the ADM-2 in early '74. It had expanded functionality and a detached keyboard.

The initials "ADM" were referred to as meaning "American Dream Machine" in some advertising.[3]


The ADM-3 followed and the first manufactured units were introduced at 1975 National Computer Conference in Anaheim, Calif., May 19–22, 1975, in booth 2348 at a price of $995.[4][2] Its innovative wave soldered single board design, which included the keyboard and all connectors, was packaged in an original clam shell enclosure.

Within weeks of the launch of the ADM-3, Cagan started to book very large orders. Its 'Dumb Terminal' nickname came from some of the original trade publication ads, and quickly caught on industry wide.[2] Due to two emerging trends, the device immediately became the best selling in the industry. Computer communications speeds were rapidly increasing, and a wave of general purpose and dedicated single application minicomputer systems were hitting the market from dozens of manufacturers. These required inexpensive operator consoles that could match the speeds. With no fast low cost printers available, the ADM-3 (painted in a variety of custom colors for the OEMs) became the de facto standard. By December 20, 1976, the widely used Teletype Model 33 KSR electromechanical printing terminal, which could only print ten characters per second, sold for $895 or $32/month, while the ADM-3, which could display up to 1,920 characters per second, went for $995 or $36/month.[5]

ADM-3 options

The original ADM-3 terminal displayed only capital letters.[6] In 1976, an option was added to allow it to display both lower and upper case.[6][7] The standard version of the terminal displayed only twelve (rather than twenty-four) rows of eighty characters.[2][6] In those days RAM was expensive, and halving the display size halved the RAM requirement[8] (and likewise all uppercase required only six bits per character to be stored rather than seven). Further optional add-ons included a graphics card enabling it to emulate a Tektronix 4010[9] and an extension port which would allow daisy chaining several ADM-3As on a single RS-232 line.[2]


In 1976, the ADM-3A was introduced.[1] The ADM-3A added support for control codes to move the cursor around on the screen, and directly position the cursor at any point in the display. It did not, however, support “clear to end of line” or “clear to end of screen”, or other more advanced codes that appeared in later terminals, such as the VT52 and VT100.

The ADM-3A's overall setup was controlled by 20[6][10] DIP switches under the nameplate at the front of the machine, beside the keyboard, including setting speed from 75 to 19,200 baud. The advanced configuration options allowed split speed connection, sending at one rate, and receiving at another.


ADM-3A keyboard layout

The 5×7 dot matrix characters were displayed in amber, green, or white phosphor on black (the cursor was 7×9). The keyboard had 59 keys. The 12-inch monochrome CRT[11] was mounted in the top half of the case, which was hinged in the back and opened like a clamshell. The CRT was typically made by Ball Brothers.[12][better source needed]

Unlike later terminals, such as the VT100, the ADM-3A did not use a microprocessor in its implementation, but instead used TTL.[10] It did, however, use RAM chips, rather than the Circulating Memory used by earlier terminals, such as the Datapoint 3300.


The use of the HJKL keys for moving the cursor in the vi editor and its descendants originated from the ADM-3A, University of California, Berkeley's Teletype Model 33 replacement, just prior to the vi editor's creation;[13][14][15][16][17] the cursor-movement arrows were printed on those four keys.[18][discuss] The Home key and tilde label printed on the key may have additionally led to the establishment of the tilde character ("~") as the representation of the home directory in many Unix shells.[discuss] The caret character is also commonly used to represent the beginning of line or "home" position in regular expression dialects.

The , , , and labels printed on the , , , , and keys were a visual reference to the control characters , , , , and that were required to move the cursor left, down, up, right, and to the top/left corner (or "Home" position) of the terminal, respectively.[19] The and functions were the standard ASCII backspace and line feed respectively, but the interpretations of , , and were new to the ADM-3A. Also common with other terminals, produced an audible beep unless disabled via DIP switch and tabbed the cursor to the next tabstop, with tabstops fixed at each 8th character position. was used to clear the screen.

Finally, the Control key was located above, not below, the Shift key—in the same place where most modern PC keyboards put the Caps Lock key.[lower-alpha 3] Many standard Unix key combinations were designed with the QWERTY layout and the ADM-3A's original Ctrl key placement in mind.[citation needed] Many of those key combinations are still in use today, even on non-Unix operating systems. Seasoned computer users familiar with the original layout often claim that the different position of the Ctrl key on modern PC keyboard layouts makes the use of Ctrl key combinations more cumbersome.[20][21][22][better source needed] Solutions exist for many operating systems to switch around the Caps Lock and Ctrl keys in software,[21][23] thus making the PC keyboard layout more closely resemble the ADM-3A's keyboard layout.

The legacy of the ADM-3A's keyboard also lives on in Japan, where the local layout follows it almost exactly. Local Mac keyboard layouts even retain the ADM-3A's position of the Control key, transposing it with the Caps Lock key.

See also


  1. About $4,000 today
  2. About $9,000 today
  3. Very early PC keyboards also had the Ctrl key located above the Shift key, just like the ADM-3A's keyboard.


  1. 1.0 1.1 "Lear Siegler Updates ADM-1, Gives ADM-3 Full Cursor Ability". Computerworld 10 (27): p. 17. July 5, 1976. ISSN 0010-4841. 
  2. 2.0 2.1 2.2 2.3 2.4 "Introducing The $995 Dumb Terminal". Computerworld 9 (31): p. S/3. July 30, 1975. ISSN 0010-4841. 
  3. "Lear Siegler advertisement". Computerworld. May 21, 1984. 
  4. "Compact ADM-3 Parading". Computerworld 9 (20): p. 57. May 14, 1975. ISSN 0010-4841. 
  5. "ComData advertisement". Computerworld 10 (51): p. 15. December 20, 1976. ISSN 0010-4841. 
  6. 6.0 6.1 6.2 6.3 "ADM-3 Maintenance Manual". 
  7. "Lower Case Feature Available for ADM-3". Computerworld 10 (13): p. 27. March 29, 1976. ISSN 0010-4841. 
  8. "ADM-3A Lower Case Option "Clone"". 
  9. "User's Manual RG-512 Retro-Graphics Card for the ADM-3A Computer Terminal". Digital Engineering, Inc.. 1980. 
  10. 10.0 10.1 "ADM-3A Maintenance Manual". 
  11. "ADM-3A CRT Replacement". 
  12. "Old tech: ADM-3A serial terminal, FreeBSD, and some fun. – Quelab". 
  13. McKusick, Marshall Kirk (January 1999). "Twenty Years of Berkeley Unix: From AT&T-Owned to Freely Redistributable". in DiBona, Chris; Ockman, Sam (in en). Open Sources: Voices from the Open Source Revolution. Sebastopol (CA): O'Reilly and Associates, Inc. ISBN 1-56592-582-3. Retrieved 23 September 2020. "Working from an editor named em that they had obtained from Professor George Coulouris at Queen Mary’s College in London, they worked to produce the line-at-a-time editor ex....With the arrival of some ADM-3a terminals offering screen-addressable cursors, Joy was finally able to write vi, bringing screen-based editing to Berkeley." 
  14. McKusick, Marshall Kirk (January 1985). "A Berkeley Odyssey". Unix Review. Retrieved 2020-09-23. 
  15. "Procedural Dungeons of Doom: The Making of Rogue – Chapter 1". 3 June 2016. 
  16. "Berkeley UNIX and the Birth of Open-Source Software". UC Regents. 11 November 2001. Retrieved 23 September 2020. "In 1969, UC Berkeley electrical engineering graduate Kenneth Thompson and his Bell Laboratories colleague Dennis Ritchie wanted to play a computer game called "Space Travel" on a dusty old mainframe computer. To do it, the two were forced to write a new operating system for the machines." 
  17. Craddock, David L. (3 June 2016). "The Making of Rogue – Chapter 1" (in en). Retrieved 23 September 2020. "By the time Toy and Wichman started at UC Santa Cruz, BSD UNIX had entered widespread usage across UC campuses and was branching out to other schools. Each new version of BSD, released on cassette tape, included handy programs written by Joy and other hackers. One program was curses, written by Ken Arnold. Arnold had written curses according to the UNIX creed: a simple tool fashioned for a specific purpose. Wielding curses like a paintbrush, users could place text such as letters, numbers, and symbols at any location on the screen." 
  18. "ADM-3A Operators Manual". pp. 3–6. 
  19. "Tenth Anniversary ADM 3A Dumb Terminal Video Display Terminal User's Reference Manual". Lear Siegler, Inc.. April 1986. pp. 1–5. 
  20. "History of the War against Caps Lock". 
  21. 21.0 21.1 "Remap Caps Lock". 
  22. "MovingTheCtrlKey". 
  23. "Swapping Capslock and Control Keys". Archived from the original on 2011-02-25. 

External links