You do not have permission to edit this page, for the following reasons:

This IP address has been blocked from editing Wikipedia.
This does not affect your ability to read Wikipedia pages.
Most people who see this message have done nothing wrong. Some kinds of blocks restrict editing from specific service providers or telecom companies in response to recent abuse or vandalism, and can sometimes affect other users who are unrelated to that abuse. Review the information below for assistance if you do not believe that you have done anything wrong.

The IP address or range 44.211.0.0/16 has been blocked (disabled) by ‪Blablubbs‬ for the following reason(s):

The IP address that you are currently using has been blocked because it is believed to be a web host provider or colocation provider. To prevent abuse, web hosts and colocation providers may be blocked from editing Wikipedia.
You will not be able to edit Wikipedia using a web host or colocation provider because it hides your IP address, much like a proxy or VPN.
We recommend that you attempt to use another connection to edit. For example, if you use a proxy or VPN to connect to the internet, turn it off when editing Wikipedia. If you edit using a mobile connection, try using a Wi-Fi connection, and vice versa. If you are using a corporate internet connection, switch to a different Wi-Fi network. If you have a Wikipedia account, please log in.
If you do not have any other way to edit Wikipedia, you will need to request an IP block exemption.

How to appeal if you are confident that your connection does not use a colocation provider's IP address:
If you are confident that you are not using a web host, you may appeal this block by adding the following text on your talk page: ((unblock|reason=Caught by a colocation web host block but this host or IP is not a web host. My IP address is _______. Place any further information here. ~~~~)). You must fill in the blank with your IP address for this block to be investigated. Your IP address can be determined here. Alternatively, if you wish to keep your IP address private you can use the unblock ticket request system. There are several reasons you might be editing using the IP address of a web host or colocation provider (such as if you are using VPN software or a business network); please use this method of appeal only if you think your IP address is in fact not a web host or colocation provider.

Administrators: The IP block exemption user right should only be applied to allow users to edit using web host in exceptional circumstances, and requests should usually be directed to the functionaries team via email. If you intend to give the IPBE user right, a CheckUser needs to take a look at the account. This can be requested most easily at SPI Quick Checkuser Requests. Unblocking an IP or IP range with this template is highly discouraged without at least contacting the blocking administrator.

This block will expire on 10:53, 20 August 2024.

Even when blocked, you will usually still be able to edit your user talk page, as well as email administrators and other editors.

For information on how to proceed, please read the FAQ for blocked users and the guideline on block appeals. The guide to appealing blocks may also be helpful.

Other useful links: Blocking policy · Help:I have been blocked
Your IP address is in a range that has been blocked on all Wikimedia Foundation wikis. The block was made by ‪AntiCompositeNumber‬. The reason given is Open proxy/Webhost: Visit the FAQ if you are affected .
- Start of block: 13:55, 18 August 2022
- Expiry of block: 13:55, 18 April 2025
Your current IP address is 44.211.186.220. The blocked range is 44.211.0.0/16. Please include all above details in any queries you make. If you believe you were blocked by mistake, you can find additional information and instructions in the No open proxies global policy. Otherwise, to discuss the block please post a request for review on Meta-Wiki. You could also send an email to the stewards VRT queue at stewards@wikimedia.org including all above details.

You can view and copy the source of this page:

((Use dmy dates|date=July 2017))
((Use British English|date=July 2017))
((More citations needed|date=July 2017))
((Infobox information appliance
| name         = English Electric KDF8
| aka          = 
| logo         = 
| logo caption = 
| image        = 
| caption      = 
| developer    = [[English Electric]]
| manufacturer = [[English Electric]]
| type         = 
| generation   = 1
| release date = ((Start date and age|1961)) (as ''KDP10'')
| lifespan     = 5 years
| baseprice    = £400,000
| unitssold    = 13
| os           = 
| cpu          = 
| CPUspeed     = 
| memory       = 
| RAMtype      = [[Magnetic core memory]]
| storage      = [[Magnetic tape]]s
| memory card  = [[Paper tape]]
| weight       = 
| predecessor  = 
| successor    = 
))
'''KDF8''' was an early British computer built by [[English Electric]] as a version of the [[RCA 501]]. By producing a software-compatible system, the intention was to reduce time and cost to develop software. However, the lengthy process of developing manufacturing capability meant that the system was soon outpaced by systems from other vendors. Only a few systems were sold during its 5 years of production.  Due to the consolidation of the British computer industry, English Electric's computer division became one of the components of what would become [[International Computers Limited|ICL]].

==Background==
During the late 1950s English Electric embarked on two major computer projects.

Firstly, English Electric built a version of the [[RCA 501]] computer which was known as the KDP10 (KDP for Kidsgrove Data Processing).  This was a machine intended for commercial data processing applications, with fixed length instructions, and capabilities for processing variable-length numeric and alpha-numeric data. RCA's original design was adapted to use the types of transistors, diodes and other components manufactured in the UK. The KDP10 was first delivered in 1961. In 1964 it was re-designated as the KDF8 and sales continued to 1965.<ref>Simon Hugh Lavington, ''Early British Computers: The Story of Vintage Computers and the People who Built Them'', Manchester University Press, 1980 ((ISBN|0719008107)) page 76</ref> The machine was essentially the same as the RCA 501 and manufactured under license so that English Electric could offer a full range of computer systems for all its customers, without the expense of developing an entirely new machine. The machine sold for £400,000.  Only 13 were sold.<ref>B. Jack Copeland (ed.), '' Alan Turing's Electronic Brain: The Struggle to Build the ACE, the World's Fastest Computer'', OUP Oxford, 2012, ((ISBN|0191625868)), pp. 166-168</ref><ref>A. Gandy,''The Early Computer Industry: Limitations of Scale and Scope'', Springer, 2012, ((ISBN|0230389112)), pp. 196-198</ref>

The second large computer to emerge from development work at [[Kidsgrove]] was the [[English Electric KDF9|KDF9]], primarily designed for scientific work.

One KDF8 was installed at the Kidsgrove (Staffordshire) site of The English Electric Company's computer bureau.  Over the years, and a succession of mergers, this organisation became English Electric Leo Marconi (EELM), International Computing Services Limited (ICSL), and finally under a joint arrangement between ICL and [[Barclay's Bank]], Baric.

==Basic features==
=== Processor/main store ===
KDF8 was a [[Transistor computer|transistor based]] machine with [[magnetic core memory]].  The core memory of the machine installed at the Kidsgrove computer bureau was upgraded from 64k to the then maximum of 96k of core memory.  KDF8 used an octal (base eight) addressing system. A machine-code instruction was fixed length, ten octal characters long. The instruction set was specifically designed for commercial use.  It had machine-code level instructions for all four of the decimal arithmetic functions operating on variable length numbers, and also had instructions for efficient manipulation of variable-length data-strings.  Not all instructions required all ten characters.  Given the minimal core memory available, programmers frequently used "spare" characters in instructions for storage of constants and similar storage-saving tricks.

KDF8 was strictly a batch processing computer, running one program at a time.  Only one compute instruction could be processed at one time, but it was also possible to have one read and/or one write instruction (typically from and to magnetic tape) executing in parallel.  A system of hardware "gates" set and checked at machine code level were used to control the degree of synchronous operation.  However, since there was no operating system of any kind, this had to be  controlled entirely at the individual program level.

The KDP10 in the service bureau was updated in situ, as the system was built with RCA germanium transistors. Part of the update was to convert the main logic to silicon transistors. There was also a three character address adder added, and the machine cycle was 15 microseconds, with six timing pulses, where sixth pulse was for settling time, thus the machine cycle was reduced to 12.5 microseconds.

The level of programmer skill to control full read/write/compute overlap, especially if data records were "batched" several to the "real" block of data on magnetic tape, was considerable, since all simultaneity checks had to be hand-coded into the program.  Automatic error-detection was essentially limited to hardware parity checks at the character level, and there were no processor hardware checks on what the programmer could do.  For example, the computer would simply stop if instructed to access a memory location beyond physical memory.

===Peripherals===
There were no magnetic disks, drums or other similar temporary backing-storage devices.  Bulk storage was limited to magnetic tapes, on open reels, each reel of which was about one inch thick and nine inches (229&nbsp;mm)  across, holding a maximum of ((Convert|2400|ft|m)) of tape.  Data and programs were kept on these tapes.  Peripheral error-checking was again limited to parity checks on all reads and writes and the use of write permit rings.  The Kidsgrove KDF8 had eight magnetic tape units on-line, each rated at 40k characters per second read/write speed.  Each tape unit was about ((convert|6|ft)) tall and ((convert|2|ft)) wide, and the processor and memory cabinets were about the same in size and number.  The Kidsgrove configuration required a large  air-conditioned room.

Eight was considered the working maximum number of tape units, one per channel, for any actual KDF8 configuration.  It was possible  for each tape channel to be split through additional hardware units into a sub-group of eight tape decks, giving a theoretical maximum of 61 on-line tape units.  (Tt least three uniquely coded I/O channel identifiers were required for other devices.)

Other tape unit/printer pairs were available, able to operate independently of the mainframe.  These provided an off-line printing facility for volume output, freeing the KDF8 to run other work.

Other peripherals included:
* a paper-tape reader (1000cps) for data and (initial) program input,
* an operator's teleprinter device (with a slow paper tape punch built-in) permitting programs to display information to the operator, and the operator to use the keyboard to punch up short program or data items on paper-tape. This teleprinter could not be used to input data directly to the computer, all operator commands had to be input through the operator's console. 
* an on-line printer, used mainly for core dumps of failed programs.

Both on and off-line printers were impact printers, capable of printing a line of either 120 or 160 characters, depending on the model   They were single type-face, no lower case.   [[Fan fold paper]] for the printers was continuous, with perforations between the pages, and sprocket-holes at each side of the paper for the paper-feed mechanism.  Custom paper sizes, with pre-printed lines/text/colours etc. were common, especially for applications like payroll, and small paper-tape control loops were needed to match page-throw size to each paper type.

==Instruction Set==
Each KDF8 machine-code instruction took the format

OO AAA RR BBB

In this representation

OO represents a two-(octal) character operation code, identifying the instruction to be performed, in the range 00 to 77,
AAA represents a six-(octal) character "A" core address ranging from 000000 to 777777. (A theoretical ((frac|1|4)) Meg directly addressable main store, an actual 96K!)
RR represents a two-character Register setting (one character for each of two possible registers numbered 1 to 7 used to modify the "A" and "B" addresses, with 0 indicating no register modification) and
BBB represents the "B" address, the same as the "A" address in format.

Instructions were read in turn from main store into registers, then executed.

Example.  An instruction to read data from the on-line paper-tape reader to locations starting at store location (octal) 200000 would look like

14 200000 00 770000          (spaces for clarity only)

Where 14 was the operation code for this type of read, 200000 was the lowest store location the data would be read to, 00 indicates that no register modification was to be done to the A or B addresses of the instruction, and 77 was the (fixed) device identifier of the paper tape reader.  (Note - 77 used as a device ID for a write operation would direct the write to the operator's teleprinter.  Embarrassing if this was due to a program error, and it was a large data block intended for mag tape.....)  The last four octal characters (0000) were not required in this instruction, and would be ignored when the instruction was processed.  Such "spare" characters were frequently, given the extremely limited main store available used by programmers to store constants.

Some aspects of the instruction set were advanced, and greatly eased programming of commercial systems.

The operation codes 51-54 did decimal arithmetic Add, Subtract, Multiply and Divide on variable length numbers, stored as decimal characters.  One end of each operand was stored at the "A" and "B" addresses of the instruction.  The other end was identified by an ISS (Item Separator Symbol), octal 74.  Thus numbers could be any length.
A "Sector Compare" instruction (Octal 43) permitted three-way conditional branching of program control depending on whether the data stored in the range from the "A" address to the "B" address was greater, less than, or equal to, the value of the same number of characters stored at locations to the left of the (previously set) "T" register, as the following Assembler language version attempts to demonstrate.

	

        Tag             Op      A-Address      RR    B-Address

        COMPARE         SET     £T                   SALARY,R
                        SC      TAXLIMIT             TAXLIMIT,R
                        CTC     BELOWTAXLIMIT        ABOVETAXLIMIT
        EQUAL           TC      EQUALTAXLIMIT

This example compares a salary with a tax limit, and jumps to one of three program locations depending on the respective values.  The ",R" Assembler convention represents the rightmost character of the named field. CTC stood for "Conditional Transfer of Control" and TC for (unconditional) Transfer of Control

In the above "compare" code, the original (KDP10?) instruction set compared from right to left, requiring the whole length of the data strings to be compared, a character at a time.  KDP8 was enhanced to compare from left to right, so the comparison could stop as soon as the relative values were clear, speeding up processing of such instructions considerably.

Variable length data was handled with the aid of specially designated characters.  The ISS or Item Separator Symbol, octal 74, usually represented as "●" was used to separate variable length data fields.  Octal 75 "<" and 76 ">" identified the start and end of a data message, Octal 777777 was by custom and practice used to identify End of File. So data such as names and addresses could be punched onto paper tape for data input as (for example)

<IAN●TAYLOR●41●HIGH STREET●KIDSGROVE●STAFFS>

Various instructions could operate directly on this variable length data, and records could be batched say ten to the batch onto magnetic tape, for efficient storage.  Given the relatively slow (by today's standards) processor and I/O rates, a significant aspect of the programmer's task was to balance the batching of data on tape, with the computing needed per record and organise the simultaneous I/O and compute operations with the aim of maximising overlap of computing with I/O and avoiding the tape-decks stopping between batch reads.

==Software==
There was no operating system.  Programs were initiated by an on-line operator, via an operator's console.  Operators were also responsible for manually clearing memory and re-setting the computer between programs, mounting and changing tapes, controlling off-line printing and the like.

Some standard software packages were available, or became available, all written in the US by the RCA organisation.  These included the following.

* A parameter-driven sort-merge program, capable of handling very large volumes of data.  Sort parameters could either be read in from the paper-tape reader, for one-off sorts, or "compiled" in (really just stored in the program).  There were extensive user "hooks" where user-supplied code could be put in at various stages of the sort/merge process.
* An assembler-language compiler called EZ-Code.  This was not used commercially for some time, since compilation time was then seen as a heavy overhead, but became increasingly used in later years.  To save on computer time, typically a programmer would do an initial compile, dry-check the program manually, re-compile, and then test and de-bug the compiled machine-code version of the program, building up a reel of paper-tape machine-code patches to the program as each correction was made.  Once a fairly robust copy was available, the changes would be replicated in Assembler and the program re-compiled and re-tested.  Frequently, the last stage was never quite completed, and it was not unknown for production programs to require machine code-patches to be loaded from paper tape for each run.  Also, a number of major commercial packages for payroll, accounts and share registration were written by Bureau staff before the Assembler compiler was accepted, and remained entirely in machine code.  A further quirk was that the I/O generation routines of the assembler were not used by one programming section, who had written their own generalized I/O package, called Tape Control, based on the COBOL file description table formats. This automated much of the error-prone programming of batching/unbatching of records and controls of simultaneous read/write operations and end-of-file conditions.
* A COBOL compiler.  This was very rarely used, early experiences not having been entirely favourable. One notable exception was a wiring design program called "WRS1", used to help design the hardware for the later English Electric [[KDF9]] and [[English Electric System 4|System 4]] range of Mainframe computers.  Another oddity was a decision table pre-processor for COBOL programs, itself written in COBOL.  This was of some interest, since bureau programming staff were at the time experimenting with using decision tables as an alternative to flowcharts.  However, while these programmers continued to hand-code in assembler from the hand-written decision tables with some success, the compilation overheads prevented the use of the pre-processor.

To optimize throughput of production programs, standard packages of software were produced by bureau programmers for payroll, sales and purchase ledgers, share registration, stock control and the like, and some applications – such as payroll – supported the processing of data from many bureau customers in one computer run, with individual parameter settings managing individual customer's requirements.  More complex client requirements were met by custom-built programs.

==Computer operation==
A very small (about 20 instructions) bootstrap loader could be held at the front of each program tape, but even this approach was not always used.  Tape labels were (with the exception of COBOL and Tape Control managed applications) almost non-existent.  A grandfather/father/son cycle of tape rotation protected production tapes from major disasters, but required careful manual controls.  Programmers (or for operational suites Production Control staff) gave the operator written instructions on which program tape and data tapes to load, on which devices, and a written summary of how to load and initiate each program.  The operator would then load the tapes, and load and initiate each program in turn manually from the console.

The console consisting of a vertical display panel about ((convert|10|in)) high by about ((convert|5|ft)) long with a similarly sized slightly angled control panel below it.  Each of these two parts was filled with labeled buttons and illuminated indicators each (roughly) one inch square.  The display section was made up of  indicators which when illuminated showed, in binary (grouped as octal) characters, the machine's current running (or static) status at the individual machine core address and register level, for the compute, read and write operations then in progress. When a program was running, this display was a kaleidoscope of quickly changing, flashing, multi-colored lights.  The control panel section consisted of press-buttons to select the next register to be set and a central part that mirrored the lay-out of a single machine core address.  Other buttons accessed more complex operations.  Use of these buttons enabled the operator to select and then directly input to the machine's core storage locations and registers the octal pattern he/she keyed in manually.  For an operator to input a single machine instruction, each of up to ten octal characters of the instruction had to be selected and keyed in as its binary pattern – each with the correct (odd) parity bit.

==See also==
* ((C|Early British computers))

==References==
<references/> 
((ICL hardware|KDF8))

((DEFAULTSORT:English Electric Kdf8))
[[Category:Early British computers]]
[[Category:ICL mainframe computers|KDF8]]
[[Category:Transistorized computers]]
[[Category:English Electric|Kdf8]]
[[Category:Computer-related introductions in 1964]]

Pages transcluded onto the current version of this page (help):

Template:Ambox (view source) (template editor protected)
Template:C (view source) (template editor protected)
Template:Catalog lookup link (view source) (template editor protected)
Template:Convert (view source) (template editor protected)
Template:DMCA (view source) (template editor protected)
Template:Dated maintenance category (view source) (template editor protected)
Template:Dated maintenance category (articles) (view source) (template editor protected)
Template:FULLROOTPAGENAME (view source) (template editor protected)
Template:Find sources mainspace (view source) (template editor protected)
Template:Frac (view source) (template editor protected)
Template:Fraction (view source) (template editor protected)
Template:Fraction/styles.css (view source) (template editor protected)
Template:Hlist/styles.css (view source) (protected)
Template:ICL hardware (edit)
Template:ISBN (view source) (template editor protected)
Template:Icon (view source) (template editor protected)
Template:Infobox (view source) (template editor protected)
Template:Infobox computing device (view source) (semi-protected)
Template:Infobox information appliance (view source) (semi-protected)
Template:Main other (view source) (protected)
Template:More citations needed (view source) (template editor protected)
Template:Navbox (view source) (template editor protected)
Template:Ns has subpages (view source) (protected)
Template:Start date and age (view source) (template editor protected)
Template:Template other (view source) (protected)
Template:Use British English (view source) (template editor protected)
Template:Use dmy dates (view source) (template editor protected)
Template:Years or months ago (view source) (template editor protected)
Template:Yesno (view source) (protected)
Template:Yesno-no (view source) (template editor protected)
Template:Yesno-yes (view source) (template editor protected)
Module:Arguments (view source) (protected)
Module:Catalog lookup link (view source) (template editor protected)
Module:Category handler (view source) (protected)
Module:Category handler/blacklist (view source) (protected)
Module:Category handler/config (view source) (protected)
Module:Category handler/data (view source) (protected)
Module:Category handler/shared (view source) (protected)
Module:Check for unknown parameters (view source) (protected)
Module:Check isxn (view source) (template editor protected)
Module:Citation/CS1/styles.css (view source) (protected)
Module:Convert (view source) (template editor protected)
Module:Convert/data (view source) (template editor protected)
Module:Convert/text (view source) (template editor protected)
Module:Find sources (view source) (template editor protected)
Module:Find sources/config (view source) (template editor protected)
Module:Find sources/links (view source) (template editor protected)
Module:Find sources/templates/Find sources mainspace (view source) (template editor protected)
Module:Icon (view source) (template editor protected)
Module:Icon/data (view source) (template editor protected)
Module:Infobox (view source) (template editor protected)
Module:Infobox/styles.css (view source) (template editor protected)
Module:InfoboxImage (view source) (template editor protected)
Module:Message box (view source) (protected)
Module:Message box/ambox.css (view source) (protected)
Module:Message box/configuration (view source) (protected)
Module:Namespace detect/config (view source) (protected)
Module:Namespace detect/data (view source) (protected)
Module:Navbar (view source) (protected)
Module:Navbar/configuration (view source) (protected)
Module:Navbar/styles.css (view source) (protected)
Module:Navbox (view source) (template editor protected)
Module:Navbox/configuration (view source) (template editor protected)
Module:Navbox/styles.css (view source) (template editor protected)
Module:Ns has subpages (view source) (protected)
Module:Unsubst (view source) (protected)
Module:Yesno (view source) (protected)

Return to English Electric KDF8.

Retrieved from "https://en.wikipedia.org/wiki/English_Electric_KDF8"