Typewriter
The automatic typing machine or punched tape machine is an electrical or electromechanical device for word processing .
The first typewriters appeared in the 1950s and were further developed into complex word processing systems in the following years.
Perforated tape writer
Components of the machine were an electric typewriter , a tape punch and one or two tape readers , which were coupled with a logic circuit made of transistors or relays .
The actions of the typing operator at the typewriter were recognized by electromechanical, electronic or optical contacts and coded in binary on a punched tape via the logic circuit . Conversely, the punched tape data could be converted into control signals for the automatic control of the typewriter using a punched tape reader. The mechanical elements of the typewriter were controlled by electromagnets .
An example of such a system is the Friden Flexowriter. This even made it possible to work with two punched tapes. In this way, z. B. a prefabricated letter can be combined with a recipient address (so-called mail merge ). This allowed serial letters to be created without having to type each letter individually.
ticker tape
The productive use of punched tape-controlled machines continued until the 1980s, as punched tape technology with seven or eight perforations per slot (without transport perforation) offered advantages. Due to the compatibility with IBM , descendants of the ASCII character set were often used .
Control characters
The control characters used to control typewriters on the punched tape are based on the ASCII character set that is still used today, which has its origin in the automated output of texts on typewriters and teleprinters as well as their storage and transmission. The first 32 characters of the set define control characters which carry out certain actions on the issuing machine and which regulate communication with a remote station. To limit yourself to the output, the following examples are the ASCII control characters (for a full list, see there) "BEL" (= " bell ", acoustic signal, usually a bell), "LF" (= " line feed ", line feed) , "CR" (= " carriage return "), "HT" (= " horizontal tab ", horizontal tab characters ) and "FF" (= " form feed ").
correction
The output on the tape punch took place immediately while writing. This coded the character to be output in binary form, usually in the form of 7 holes per row. A perforation represented a set bit. The correction of a character that had been "perforated" in this way was possible by subsequently punching all seven bits in the position of the wrong character at the same time. Holes punched in a punched tape could not simply be refilled. A row with seven set bits was ignored by the issuing machines. & b1111111 (= 127 or 7F) represents the ASCII control character "DEL" (= " deleted "). Any number of consecutive characters could be deleted.
At the beginning and at the end of a perforated tape (around ten to 15 DEL), these perforations ensured that the perforated tape could be easily inserted into the reader because the transport perforation was available and there was space for the first valid character.
Text modules
Punched tapes offered the opportunity to work with text modules . For this purpose, either the respective punched tape sections were simply glued together or the punched tape to be used was placed one after the other in a reader and punched in the document to be generated to the desired location.
Duplication
Punched tapes could be duplicated. For this purpose, the swelling perforated strip was inserted and processed by the machine. In the same step, all actions, whether automatically read in or entered manually, were then output on a new punched tape. The new punched tape then contained a version that had been corrected for errors, since corrections and stop commands were not automatically output on the new punched tape.
Serial letters
Two reading stations were required for the automated creation of form letters . The punched tape with the address data (including individually variable salutation and data) was inserted in the first reading station, and the serial letter glued together to form a ring in the second. Control codes in both strips regulated the switchover between the two reading stations.
If the machine was fed with continuous paper , it rattled until either the address data was processed or the paper ran out. In the first case the process was completely completed, in the second case the operator had to insert the next box of paper.
Console (computer)
The Friden Flexowriter (and others) were suitable as a console for computers from the 50s to 70s.
Individual evidence
- ↑ Computerwoche 46/1977: Do you know the Röllchen-Speicher? Archived copy ( Memento of the original dated December 8, 2008 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Friden Flexowriter on vimeo.com Vimeo
- ↑ Computer Museum of the Faculty of Computer Science at the University of Stuttgart Friden Flexowriter
