A Hazeltine 1500 being used as the primary interface to a SWTPC 6800 microcomputer.
The Hazeltine 1500 was a popular smart terminal introduced by Hazeltine Corporation in April 1977 at a price of $1,125(equivalent to $5,400 in 2022). Using a microprocessor and semiconductor random access memory, it implemented the basic features of the earlier Hazeltine 2000 in a much smaller and less expensive system, less than half the price. It came to market just as the microcomputer revolution was taking off, and the 1500 was very popular among early hobbyist users.
Two modified versions were introduced in June 1977, the $1,395Hazeltine 1510 and $1,650Hazeltine 1520. The 1510 added a simple batch mode system that allowed the user to type in values without them being sent to the host system. When the SEND key was pressed, all the "foreground" data that had been typed in was sent all at once. The 1520 was a 1510 with an added printer port that could support serial or parallel computer printers.
The final entry to the 1500 series was the Hazeltine 1552 introduced in August 1979 at $1,500. It added a VT52 emulation mode, separate cursor keys, and graphics characters.[1]
Basic features
The 1500 used an Intel 8080A processor with 2kB of ROM for the basic operations, and 2kB of RAM as the character buffer (4kB in the 1510/1520). Characters were drawn using a 7 column by 10 row pattern within a larger 9 by 11 cell. The display showed 80 columns by 24 rows, a widespread standard at that time. The 12" CRT used P4 "white" phosphor.[2]
Like earlier models in the Hazeltine line, the 1500 supported both an RS-232 interface, with speeds from 110 up to 19,200bit/s, as well as a 20mA current loop, used by teletype systems and still common due to the widespread use of Teletype Model 33 as ad hoc terminals.[2] 19,200bit/s was relatively fast for the era, most terminals of similar vintage topped out at 9,600.[lower-alpha 1]
Commands
The command set for Hazeltine terminals was fairly simple, consisting mostly of line editing and cursor positioning commands. The tilde, ~ was used as the escape character, or as they referred to it, the "lead-in code". The 1510/1520 also allowed ESC to be used as the lead-in.[5]
Simple one-letter commands following the lead-in included DC2 for cursor-to-home (upper left corner of the screen), FF for up-cursor, VT (vertical tab) for down-cursor, BS (backspace) for cursor-left and DLE for cursor-right, and FS (form separator) for clear screen.[6]SI cleared to the end of the line, ETB to the end of the screen.[7]DC3 deleted the line and moved any data below it up while SUB inserted a line and pushed lines down.[8]
The cursor could be positioned anywhere on the screen using DC1 and following that with two ASCII characters for the X and Y locations. The ASCII could be offset by any multiple of 32, so for instance, one could move to Y location (row) 10 by sending LF, ASCII code 10, or by sending *, ASCII code 42, 32+10. The advantage of adding 32 to the value is that it shifts it into the printable character range, which is more likely to work on all serial links. The same was true for the X address, but because the locations were 0 to 79, rather than 0 to 23 for Y, shifting higher addresses in this manner might put them out of the printable range again. They suggested transmitting 0 through 30 using codes 96 through 126.[9]ENQ would return the current cursor location as two characters separated by a carriage return.[10]
Sending - caused the terminal to send a single character in return, encoding the terminal status in the lower 6 bits. Bits 0, 1 and 7 were not used and always zero. Bit 2 returned whether it was half duplex while 3 was full duplex. Bit 4 was 1 if there was a parity error on the last transmission. 5 and 6 encoded the end-of-line character being used, 00 was CR, 01 was ETX, 10 for EOT, and 11 for none.[11]
One unique feature of the Hazeltine systems was the difference between normal-intensity "background" characters and higher-intensity "foreground" characters. The system was normally in background mode and any data sent to it was displayed normally. Sending the "foreground follows" instruction, US (unit separator), all following data was displayed in foreground mode. Sending background follows, EM (end-of-medium) returned to background mode.[12] Sending CAN cleared to the end of the screen like ETB, but filled it with foreground spaces.[7]GS was similar to clear screen, but removed only the foreground.[13]
Sending NAK locked the keyboard, while ACK unlocked it again.[8]
Batch and block commands
The 1510 and 1520 included modifications of the foreground/background system that allowed them to operate in "format mode", what would be known as block mode in IBM parlance. In this case, data in foreground style was also referred to as "unprotected" while that in the background was "protected". As with the base model 1510, one could clear out only the foreground data, or all data, normally defaulting to only clearing the unprotected foreground. [5]
Format mode is entered with a ~#.[14] When the terminal is put into format mode and the user types data into the terminal, the data is not sent to the host, it is simply stored in a second 2kB buffer. When the user presses the SEND key, all data in the foreground is sent to the host in a single stream. The host could also trigger the send operation by sending ~SO to the terminal. The system could be set to send different bits of data; sending ~. to the terminal sent back only the line the cursor was in, ~( would instead send everything on the screen from the home position to the cursor.[5]
Similar to format mode is batch mode, which differed only in that it sent data whenever the input for one field was complete. When the user pressed return or tab to advance, the data for the preceding field was automatically sent and the cursor advanced to the next foreground field. Batch mode was entered using ~%.[5]
While in format mode, the TAB character was used to move from field-to-field, skipping over any text that was in background style to the next unused field or foreground style. It also added a back-tab to move backwards through the fields, sending ~DC4.[11]
The user could also trigger whether new data would be accepted by pressing the LOCAL key. When this was on, the terminal only accepted input from the keyboard, ignoring data from the host. This mode ended when the user pressed LOCAL again, or SEND.[15]
The status character changed on the 1510/1520 to return more information. Bit 0 now indicated if the print buffer was empty, and 1 whether or not the printer was in online mode (echoing everything from the host). Bits 2 and 3 now encoded the format mode, 00 was off, 01 was batch, 10 for page, and 11 for line.[11]
Printer commands
The 1520 included a printer buffer able to hold one screen of data, added a selection of commands to control it, and a PRINT key to turn it on and off manually.[16] The terminal could be set to send all data to the screen, the printer, or both —~/ turned on the printer and sent data from the host to the screen and printer, ~* sent it to the printer only, and ~? turned off the printer and sent data to the screen (the default mode). Pressing the PRINT key, or sending ~RS from the host, would dump the current screen to the printer.[17]
In popular culture
The 1500 model famously appears on the cover of Kraftwerk's 1981 album Computer World. The 1500 model also appeared in Stereolab's video clip Miss Modular.[18]
Notes
↑ The VT52, for instance,[3] or even Hazeltine's own 2000.[4]
Related Research Articles
In computing and telecommunication, a control character or non-printing character (NPC) is a code point in a character set that does not represent a written character or symbol. They are used as in-band signaling to cause effects other than the addition of a symbol to the text. All other characters are mainly graphic characters, also known as printing characters, except perhaps for "space" characters. In the ASCII standard there are 33 control characters, such as code 7, BEL, which rings a terminal bell.
The IBM 3270 is a family of block oriented display and printer computer terminals introduced by IBM in 1971 and normally used to communicate with IBM mainframes. The 3270 was the successor to the IBM 2260 display terminal. Due to the text color on the original models, these terminals are informally known as green screen terminals. Unlike a character-oriented terminal, the 3270 minimizes the number of I/O interrupts required by transferring large blocks of data known as data streams, and uses a high speed proprietary communications interface, using coaxial cable.
A terminal emulator, or terminal application, is a computer program that emulates a video terminal within some other display architecture. Though typically synonymous with a shell or text terminal, the term terminal covers all remote terminals, including graphical interfaces. A terminal emulator inside a graphical user interface is often called a terminal window.
The VT100 is a video terminal, introduced in August 1978 by Digital Equipment Corporation (DEC). It was one of the first terminals to support ANSI escape codes for cursor control and other tasks, and added a number of extended codes for special features like controlling the status lights on the keyboard. This led to rapid uptake of the ANSI standard, which became the de facto standard for hardware video terminals and later terminal emulators.
In computer science, an escape sequence is a combination of characters that has a meaning other than the literal characters contained therein; it is marked by one or more preceding characters.
ANSI escape sequences are a standard for in-band signaling to control cursor location, color, font styling, and other options on video text terminals and terminal emulators. Certain sequences of bytes, most starting with an ASCII escape character and a bracket character, are embedded into text. The terminal interprets these sequences as commands, rather than text to display verbatim.
A computer terminal is an electronic or electromechanical hardware device that can be used for entering data into, and transcribing data from, a computer or a computing system. The teletype was an example of an early-day hard-copy terminal and predated the use of a computer screen by decades.
The Tektronix 4010 series was a family of text-and-graphics computer terminals based on storage-tube technology created by Tektronix. Several members of the family were introduced during the 1970s, the best known being the 11-inch 4010 and 19-inch 4014, along with the less popular 25-inch 4016. They were widely used in the computer-aided design market in the 1970s and early 1980s.
The VT50 was a CRT-based computer terminal introduced by Digital Equipment Corporation (DEC) in July 1974. It provided a display with 12 rows and 80 columns of upper-case text, and used an expanded set of control characters and forward-only scrolling based on the earlier VT05. DEC documentation of the era refers to the terminals as the DECscope, a name that was otherwise almost never seen.
The Teletype Model 33 is an electromechanical teleprinter designed for light-duty office use. It is less rugged and cost less than earlier Teletype models. The Teletype Corporation introduced the Model 33 as a commercial product in 1963, after it had originally been designed for the United States Navy. The Model 33 was produced in three versions:
The HP 2640A and other HP 264X models were block-mode "smart" and intelligent ASCII standard serial terminals produced by Hewlett-Packard using the Intel 8008 and 8080 microprocessors.
The IBM 2741 is a printing computer terminal that was introduced in 1965. Compared to the teletypewriter machines that were commonly used as printing terminals at the time, the 2741 offers 50% higher speed, much higher quality printing, quieter operation, interchangeable type fonts, and both upper and lower case letters.
The CDC 1700 was a 16-bit word minicomputer, manufactured by the Control Data Corporation with deliveries beginning in May 1966.
Sixel, short for "six pixels", is a bitmap graphics format supported by terminals and printers from DEC. It consists of a pattern six pixels high and one wide, resulting in 64 possible patterns. Each possible pattern is assigned an ASCII character, making the sixels easy to transmit on 7-bit serial links.
Termcap is a legacy software library and database used on Unix-like computers that enables programs to use display computer terminals in a device-independent manner, which greatly simplifies the process of writing portable text mode applications. It was superseded by terminfo database used by ncurses, tput, and others programs.
The DECwriter series was a family of computer terminals from Digital Equipment Corporation (DEC). They were typically used in a fashion similar to a teletype, with a computer output being printed to paper and the user inputting information on the keyboard. In contrast to teletypes, the DECwriters were based on dot matrix printer technology, one of the first examples of such a system to be introduced. Versions lacking a keyboard were also available for use as computer printers, which eventually became the only models as smart terminals became the main way to interact with mainframes and minicomputers in the 1980s.
The POSIX terminal interface is the generalized abstraction, comprising both an application programming interface for programs, and a set of behavioural expectations for users of a terminal, as defined by the POSIX standard and the Single Unix Specification. It is a historical development from the terminal interfaces of BSD version 4 and Seventh Edition Unix.
The VT320 is an ANSI standard computer terminal introduced by Digital Equipment Corporation (DEC) in 1987. The VT320 is the text-only version, while the VT330 adds monochrome ReGIS, Sixel and Tektronix 4010 graphics, and the VT340 adds color.
Waveform graphics is a simple vector graphics system introduced by Digital Equipment Corporation (DEC) on the VT55 and VT105 terminals in the mid-1970s. It was used to produce graphics output from mainframes and minicomputers. DEC used the term "waveform graphics" to refer specifically to the hardware, but it was used more generally to describe the whole system.
The Hazeltine 2000 is one of the first general-purpose "smart" computer terminals, introduced in October 1970 at a price of $2,995. While earlier terminal systems included "smart" editing features, notably the IBM 2260, the Hazeltine 2000 was the first that used a standard RS-232 interface and sent its control sequences in the data stream. It could be attached to any contemporary minicomputer or mainframe that had a serial port and used ASCII-standard character sets.
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
