View source for IBM 650

{{Short description|Vacuum-tube 1950s computer system}}
{{Infobox information appliance
| name = IBM 650
| cost = 
| successor = [[IBM 7070]] (hi-end){{br}}[[IBM 1620]] (low-end)
| logo_size = 120px
| logo_caption = 
| image = IBM 650 EMMA.jpg
| image_size = 270px
| caption = Part of the first IBM 650 computer in Norway (1959), known as "EMMA". 650 Console Unit (right, an exterior side panel is open), 533 Card Read Punch unit (middle, input-output). 655 Power Unit is missing. Punched card sorter (left, not part of the 650). Now at [[Norwegian Museum of Science and Technology]] in [[Oslo]].
| type = [[Digital computer]]
| designfirm = 
| manufacturer = 
| release date = {{Start date and age|1954}}
| discontinued = 
| processor = 
| memory = 
| logo = IBM Logo 1947 1956.svg
| frequency = 
| slots = 
| coprocessor = 
| connection = 
| ports = 
| power = 
| speed = 
| language = 
| weight = 
| dimensions = 
| predecessor = [[IBM CPC]] ([[IBM 604|604]], 605)
| related = [[IBM 701]], [[IBM 702]]; {{br}}[[IBM 608]]
| family = 
}}
[[File:IBM 650 at Texas A&M.jpg|thumb|IBM 650 at Texas A&M University. The IBM 533 Card Read Punch unit is on the right.]]
[[File:IBM 650.002 - MUNCYT.jpg|thumb|IBM 650 console panel, showing bi-quinary indicators.<ref name="650-manual-of-operation"/>{{rp|p. 47ff}}  Note wear marks around frequently used switches, lower right. Collection of the Museo Nacional de Ciencia y Tecnología. A Coruña (Galicia, Spain).]]
[[File:IBM 650 panel close-up of bi-quinary indicators.jpg|thumb|Close-up of bi-quinary indicators]]
[[File:Memoria a tamburo magnetico per sistema IBM 650 - Museo scienza tecnologia Milano D1171.jpg|thumb|Memory drum from an IBM 650]] 
[[File:Coruña, MUNCYT 01-21b.JPG|thumb|Side view of an IBM 650 Console Unit. First computer in Spain (1959) now at [[National Museum of Science and Technology (Spain)|National Museum of Science and Technology]] in [[A Coruña]]]]

The '''IBM 650 Magnetic Drum Data-Processing Machine''' is an early [[digital computer]] produced by [[IBM]] in the mid-1950s.<ref>{{cite web |url=https://www.ibm.com/ibm/history/exhibits/650/650_ph06.html |title=IBM Archives: IBM 650 installation with IBM 727 Magnetic Tape Unit and IBM 355 Disk Storage |website=IBM |location=US |access-date=September 5, 2019 |archive-url=https://web.archive.org/web/20230409023954/https://www.ibm.com/ibm/history/exhibits/650/650_ph06.html |archive-date=2023-04-09 |url-status=dead}}</ref><ref>{{cite web |url=https://www.ibm.com/ibm/history/exhibits/650/650_ph05.html |title=IBM Archives: IBM 650 Assembly at Endicott plant |website=IBM |location=US |access-date=September 5, 2019 |archive-url=https://web.archive.org/web/20231023160555/https://www.ibm.com/ibm/history/exhibits/650/650_ph05.html |archive-date=2023-10-23 |url-status=dead}}</ref> It was the first mass-produced computer in the world.<ref>{{cite web |title=History Of Computers 1937-2011 |url=https://www.cs.odu.edu/~tkennedy/cs300/development/Public/M01-HistoryOfComputers/index.html |website=Old Dominion University |access-date=June 22, 2021}}</ref><ref>{{cite web |title=IBM in the Computer Era |url=https://mncomputinghistory.com/ibm-in-the-computer-era/ |website=The Minnesota Computing History Project |date=28 June 2018 |access-date=June 21, 2021}}</ref> Almost 2,000 systems were produced, the last in 1962,<ref>{{cite book|last=Pugh|first=Emerson W.|url=https://archive.org/details/buildingibmshapi00pugh|title=Building IBM: Shaping an Industry and Its Technology|publisher=MIT Press|year=1995|isbn=978-0-262-16147-3|page=[https://archive.org/details/buildingibmshapi00pugh/page/n191 182]|url-access=limited}}</ref><ref name=":0" /> and it was the first computer to make a meaningful profit.<ref name=":0" /> The first one was installed in late 1954 and the IBM 650 was the most popular computer of the 1950s.<ref>{{cite book |last=Davis |first=Gordon B. |year=1971 |title=Introduction to Electronic Computers|url=https://archive.org/details/introductiontoel00davi |url-access=registration |edition=Second |page=[https://archive.org/details/introductiontoel00davi/page/10 10] |location=New York |publisher=McGraw-Hill |isbn=978-0-070-15821-4}}</ref>

The 650 was offered to business, scientific and engineering users as a slower and less expensive alternative to the [[IBM 701]] and [[IBM 702]] computers, which were for scientific and business purposes respectively.<ref name=":0">{{Cite web|last=|first=|date=|title=The IBM 650 Magnetic Drum Calculator|url=http://www.columbia.edu/cu/computinghistory/650.html|access-date=|website=Columbia.edu}}</ref> It was also marketed to users of [[unit record equipment|punched card machines]] who were upgrading from [[Unit record equipment#Calculating|calculating punches]], such as the [[IBM 604]], to computers.<ref name="650-manual-of-operation">{{Cite book|url=http://www.bitsavers.org/pdf/ibm/650/22-6060-2_650_OperMan.pdf|title=IBM 650 Magnetic Drum Data-Processing Machine: Manual of Operation|publisher=IBM|year=1955|id=22-6060-1}}</ref>{{rp|5}}<ref>{{cite web |url=https://www.ibm.com/ibm/history/exhibits/650/650_cu1.html |title=IBM Archives: 650 Customers |website=IBM |archive-url=https://web.archive.org/web/20230725133257/https://www.ibm.com/ibm/history/exhibits/650/650_cu1.html |archive-date=2023-07-25 |url-status=dead}}</ref>

Because of its relatively low cost and ease of [[Computer programming|programming]], the 650 was used to pioneer a wide variety of applications, from modeling submarine crew performance<ref>{{cite book|last=Gray|first=Wayne D.|url=https://archive.org/details/integratedmodels00gray|title=Integrated Models of Cognition Systems|publisher=Oxford University Press|year=2007|isbn=978-0-19-518919-3|location=New York|page=[https://archive.org/details/integratedmodels00gray/page/n54 36]|url-access=limited}}</ref> to teaching high school and college students computer programming. The IBM 650 became highly popular in universities, where a generation of students first learned programming.<ref>{{Cite web|last=|first=|date=|title=IBM 650 magnetic drum calculator introduced|url=https://www.computerhistory.org/timeline/1954/|access-date=|website=Computerhistory}}</ref>

It was announced in 1953 and in 1956 enhanced as the '''IBM 650 RAMAC''' with the addition of up to four disk storage units.<ref>{{cite web |url=https://www.ibm.com/ibm/history/exhibits/650/650_pr2.html |title=IBM Archives: 650 RAMAC announcement press release |website=IBM |archive-url=https://web.archive.org/web/20230609092034/https://www.ibm.com/ibm/history/exhibits/650/650_pr2.html |archive-date=2023-06-09 |url-status=dead}}</ref> The purchase price for the bare IBM 650 console, without the reader punch unit, was $150,000 in 1959,<ref>{{Cite web |date=2003-01-23 |title=IBM Archives: IBM 650 Model 4 announcement press release |url=https://www.ibm.com/ibm/history/exhibits/650/650_pr4.html |access-date=2023-07-25 |website=IBM |language=en-US |archive-url=https://web.archive.org/web/20231023160555/https://www.ibm.com/ibm/history/exhibits/650/650_pr4.html |archive-date=2023-10-23 |url-status=dead}}</ref> or roughly $1,500,000 as of 2023. Support for the 650 and its component units was withdrawn in 1969.

The 650 was a [[Memory address|two-address]], [[bi-quinary coded decimal]] computer (both data and addresses were decimal), with [[Computer memory|memory]] on a rotating magnetic [[drum memory|drum]].  [[Character (computing)|Character]] support was provided by the input/output units converting punched card alphabetical and special [[character encoding]]s to/from a two-digit decimal code.

The 650 was clocked at a frequency of 125 kHz.<ref>{{Cite conference |last=Royse |first=David |book-title=Papers presented at the February 26-28, 1957, western joint computer conference: Techniques for reliability on - IRE-AIEE-ACM '57 (Western) |date=1957 |title=The IBM 650 RAMAC system disk storage operation |url=http://portal.acm.org/citation.cfm?doid=1455567.1455576 |language=en |publisher=ACM Press |pages=43–49 |doi=10.1145/1455567.1455576|doi-access=free }}</ref> It could add or subtract in 1.63 milliseconds, multiply in 12.96 ms, and divide in 16.90 ms. The average speed of the 650 was estimated to be around 27.6 ms per instruction, or roughly 40 instructions per second.<ref name="KnuthNotes">{{Cite web |title=Knuth Biographic Notes |url=https://softpanorama.org/People/Knuth/knuth_biographic_notes.shtml |access-date=2023-07-25 |website=softpanorama.org}}</ref>

[[Donald Knuth]]'s series of books ''[[The Art of Computer Programming]]'' is famously dedicated to a 650.<ref name="KnuthNotes"/>

==History==
The first 650 was installed on December 8, 1954 in the [[Comptroller|controller]]'s department of the [[John Hancock Financial|John Hancock Mutual Life Insurance Company]] in Boston.<ref>{{cite web|url=https://www.ibm.com/ibm/history/exhibits/650/650_ch1.html|title=IBM Archives: 650 Chronology|archive-url=https://web.archive.org/web/20230417002435/https://www.ibm.com/ibm/history/exhibits/650/650_ch1.html|archive-date=2023-04-17|url-status=dead}}</ref>

The [[IBM 7070]] (signed 10-digit decimal words), announced 1958, was expected to be a "common successor to at least the 650 and the [[IBM 705|[IBM] 705]]".<ref>{{cite book |title=IBM's Early Computers |last1=Bashe |first1=Charles J. |last2=Johnson |first2=Lyle R |last3=Palmer |first3=John H. |last4=Pugh |first4=Emerson W. |year=1986 |publisher=MIT |isbn=0-262-02225-7 |page=[https://archive.org/details/ibmsearlycompute00bash/page/473 473] |url-access=registration |url=https://archive.org/details/ibmsearlycompute00bash/page/473 }}</ref> The [[IBM 1620]] (variable-length decimal), introduced in 1959, addressed the lower end of the market. The [[UNIVAC Solid State]] (a two-address computer, signed 10-digit decimal words) was announced by Sperry Rand in December 1958 as a response to the 650.  None of these had an instruction set that was compatible with the 650.

==Hardware==
The basic 650 system consisted of three units:<ref name=650c>{{cite web |url=https://www.ibm.com/ibm/history/exhibits/650/650_cm1.html |title=IBM Archives: 650 Components |archive-url=https://web.archive.org/web/20230725133256/https://www.ibm.com/ibm/history/exhibits/650/650_cm1.html |archive-date=2023-07-25 |url-status=dead}}</ref>

* IBM 650 Console Unit<ref>{{cite web |url=https://www.ibm.com/ibm/history/exhibits/650/650_ph01.html |title=IBM Archives: IBM 650 Console Unit |website=IBM |archive-url=https://web.archive.org/web/20231023164304/https://www.ibm.com/ibm/history/exhibits/650/650_ph01.html |archive-date=2023-10-23 |url-status=dead}}</ref> housed the magnetic drum storage, arithmetical device (using vacuum tubes) and the operator's console.
* [[IBM 655]] Power Unit<ref>{{cite web |url=https://www.ibm.com/ibm/history/exhibits/650/650_ph15.html |title=IBM Archives: IBM 655 Power Unit |website=IBM |archive-url=https://web.archive.org/web/20230408154257/https://www.ibm.com/ibm/history/exhibits/650/650_ph15.html |archive-date=2023-04-08 |url-status=dead}}</ref>
* [[IBM 533]] or [[IBM 537]] Card Read Punch Unit<ref>Other IBM names for the 533 included ''Input-Output Unit'' and ''Read-Punch Unit''.</ref><ref>{{cite web |url=https://www.ibm.com/ibm/history/exhibits/650/650_ph13.html |title=IBM Archives: IBM 533 Card Read Punch |website=IBM |archive-url=https://web.archive.org/web/20230408161301/https://www.ibm.com/ibm/history/exhibits/650/650_ph13.html |archive-date=2023-04-08 |url-status=dead}}</ref><ref>{{cite web |url=https://www.ibm.com/ibm/history/exhibits/650/650_ph14.html |title=IBM Archives: IBM 537 Card Read Punch |website=IBM |archive-url=https://web.archive.org/web/20230409012830/https://www.ibm.com/ibm/history/exhibits/650/650_ph14.html |archive-date=2023-04-09 |url-status=dead}}</ref> The IBM 533 had separate feeds for reading and punching; the IBM 537 had one feed, thus could read and then punch into the same card.
Weight: {{convert|5400-6263|lb|ST MT|1}}.<ref>{{cite book |title=Physical Planning Installation Manual 650 System |url=http://www.bitsavers.org/pdf/ibm/650/21-7643-1_650_InstallMan.pdf |page=32 |publisher=IBM |via=Bitsavers |date=October 1, 1957 |access-date=May 31, 2018}}</ref><ref>{{cite book |title=Customer Engineering Manual of Instruction |url=http://www.bitsavers.org/pdf/ibm/650/22-6284-1_650_CE_Manual_of_Instruction.pdf |page=I-17 |publisher=IBM |via=Bitsavers |year=1956 |access-date=May 31, 2018}}</ref>

Optional units:<ref name=650c/>

* IBM 46 Tape To Card Punch, Model 3<ref name=650c />
* IBM 47 Tape To Card Printing Punch, Model 3<ref name=650c />
* [[IBM 355]] Disk Storage Unit<ref>{{cite web |url=https://www.ibm.com/ibm/history/exhibits/650/650_ph07.html |title=IBM Archives: IBM 355 Disk Storage |website=IBM |archive-url=https://web.archive.org/web/20230409022452/https://www.ibm.com/ibm/history/exhibits/650/650_ph07.html |archive-date=2023-04-09 |url-status=dead}}</ref>  Systems with a disk unit were known as ''IBM 650 RAMAC Data Processing Systems''
* [[IBM 407]] Accounting Machine<ref>{{cite web |url=https://www.ibm.com/ibm/history/exhibits/vintage/vintage_4506VV4007.html |title=IBM Archives: IBM 407 accounting machine |website=IBM |archive-url=https://web.archive.org/web/20230703223109/https://www.ibm.com/ibm/history/exhibits/vintage/vintage_4506VV4007.html |archive-date=2023-07-03 |url-status=dead}}</ref>
* [[IBM 543]] Card Reader Unit
* [[IBM 544]] Card Punch Unit
* [[IBM 652]] Control Unit (magnetic tape, disk)<ref>{{cite web |url=https://www.ibm.com/ibm/history/exhibits/650/650_ph12.html |title=IBM Archives: IBM 652 Control Unit |website=IBM |archive-url=https://web.archive.org/web/20230408162804/https://www.ibm.com/ibm/history/exhibits/650/650_ph12.html |archive-date=2023-04-08 |url-status=dead}}</ref>
* [[IBM 653]] Storage Unit (magnetic tape, disk, core storage, index registers, [[floating-point arithmetic]])<ref>{{cite web |url=https://www.ibm.com/ibm/history/exhibits/650/650_ph11.html |title=IBM Archives: IBM 653 Auxiliary Unit |website=IBM |archive-url=https://web.archive.org/web/20230409012811/https://www.ibm.com/ibm/history/exhibits/650/650_ph11.html |archive-date=2023-04-09 |url-status=dead}}</ref>
* [[IBM 654]] Auxiliary Alphabetic Unit
* [[IBM 727]] Magnetic Tape Unit
* [[IBM 838]] Inquiry Station<ref>{{cite web |url=https://www.ibm.com/ibm/history/exhibits/650/650_ph16.html |title=IBM Archives: IBM 838 Inquiry Station |website=IBM |archive-url=https://web.archive.org/web/20230408112022/https://www.ibm.com/ibm/history/exhibits/650/650_ph16.html |archive-date=2023-04-08 |url-status=dead}}</ref>

===Main memory===
Rotating [[drum memory]] provided 1,000, 2,000, or 4,000 [[Word (computer architecture)|words]] of memory at addresses 0000 to 0999, 1999, or 3999 respectively. Each word had 10 [[Bi-quinary coded decimal#IBM650code|bi-quinary coded decimal digits]], representing a signed 10-digit number or five characters. (Counting a bi-quinary coded digit as seven bits, 4000 words would be equivalent to 35 kilobytes.)<ref>{{cite web |url=https://www.ibm.com/ibm/history/exhibits/650/650_ph09.html |title=IBM Archives: IBM 650 Magnetic Drum |website=IBM |archive-url=https://web.archive.org/web/20230207023510/https://www.ibm.com/ibm/history/exhibits/650/650_ph09.html |archive-date=2023-02-07 |url-status=dead}}</ref><ref>{{cite web |url=https://www.ibm.com/ibm/history/exhibits/650/650_pr4.html |title=IBM Archives: IBM 650 Model 4 announcement |website=IBM |archive-url=https://web.archive.org/web/20231023160555/https://www.ibm.com/ibm/history/exhibits/650/650_pr4.html |archive-date=2023-10-23 |url-status=dead}}</ref>  Words on the drums were organized in bands around the drum, fifty words per band, and 20, 40, or 80 bands for the respective models. A word could be accessed when its location on the drum surface passed under the read/write heads during rotation (rotating at 12,500 [[Revolutions per minute|rpm]], the non-optimized average access time was 2.5 [[millisecond|ms]]).  Because of this timing, the second address in each instruction was the address of the next instruction.  Programs could then be [[Optimum programming|optimized]] by placing instructions at addresses that would be immediately accessible when execution of the previous instruction was completed. IBM provided a form with ten columns and 200 rows to allow programmers to keep track of where they put instructions and data. Later an [[assembly language|assembler]], SOAP (Symbolic Optimal Assembly Program), was provided that performed rough optimization.<ref>{{cite web|url=https://www.drdobbs.com/the-ibm-650/184404809|title=The IBM 650|first=Herb|last=Kugel|date=October 22, 2001|publisher=Dr. Dobb's}}</ref><ref name=soap />

The [[LGP-30]], [[Bendix G-15]] and [[IBM 305 RAMAC]] computers used vacuum tubes and drum memory too, but they were quite different from the IBM 650.

Instructions read from the drum went to a ''program register'' (in current terminology, an [[instruction register]]). Data read from the drum went through a 10-digit ''distributor.'' The 650 had a 20-digit [[Accumulator (computing)|''accumulator'']], divided into 10-digit lower and upper accumulators with a common sign.  Arithmetic was performed by a one-digit adder.  The console (10 digit switches, one sign switch, and 10 bi-quinary display lights), distributor, lower and upper accumulators were all addressable; 8000, 8001, 8002, 8003 respectively.

===IBM 653 Storage Unit===
The optional IBM 653 Storage Unit, was introduced on May 3, 1955, ultimately providing up to five features:<ref name=CPU-ext/>

* Magnetic tape controller (for IBM 727 Magnetic Tape units) (10 extra operation codes)
* Disk storage controller (1956 enhancement for then new IBM 355 Disk Storage Unit) (five extra operation codes)
* Sixty 10-digit words of [[core memory|magnetic core]] memory at addresses 9000 to 9059. This small ''fast memory'' had an access time of 96[[microsecond|μs]], a 26-fold improvement relative to the rotating drum. This feature added five operation codes and was needed as a buffer for tape and disk I/O. The 60 words could also be used by programs to speed up inner loops and table lookups.
* Three four-digit [[index register]]s at addresses 8005 to 8007; drum addresses were indexed by adding 2000, 4000 or 6000 to them, core addresses were indexed by adding 0200, 0400 or 0600 to them.  If the system had the 4000 word drum then indexing was by adding 4000 to the first address for index register A, adding 4000 to the second address for index register B, and by adding 4000 to each of the two addresses for index register C (the indexing for 4000-word systems only applied to the first address). The 4000-word systems required [[Transistor computer|transistorized]] read/write circuitry for the drum memory and were available before 1963. (18 extra operation codes)
* [[Floating point]] – arithmetic instructions supported an eight-digit mantissa and two-digit characteristic (offset exponent) – '''MMMMMMMMCC''', providing a range of ±0.00000001E-50 to ±0.99999999E+49. (seven extra operation codes)

==Instruction set==
The 650 [[Instruction set|instructions]] consisted of a two-digit [[Opcode|operation code]], a four-digit data address and the four-digit address of the next instruction. The sign was ignored on the basic machine, but was used on machines with optional features. The base machine had 44 operation codes.  Additional operation codes were provided for options, such as floating point, core storage, index registers and additional I/O devices.  With all options installed, there were 97 operation codes.<ref name=CPU-ext>[http://www.bitsavers.org/pdf/ibm/650/24-5003-0_CPU_Extensions.pdf IBM 650 CPU Extensions]</ref>

The Table lookup (TLU) instruction could high-equal compare a referenced 10-digit word with 48 consecutive words on the same drum band in one 5ms revolution and then switch to the next band in time for the next 48 words.  This feat was about one-third the speed of a one-thousand times faster binary machine in 1963 (1,500 microseconds on the IBM 7040 to 5,000 microseconds on the 650) for looking up 46 entries as long as both were programmed in assembler. There was an optional Table lookup Equal instruction, with the same performance.

The Read (RD) instruction read an 80-column card of numeric data into ten memory words; the distribution of digits to words determined by the card reader's [[Plugboard#Unit record equipment|control panel wiring]].  When used with the 533 Reader Punch unit's Alphabetic device, a combination of numeric and [[alphanumeric]] columns (maximum of 30 alphanumeric columns) could be read.<ref name="650-manual-of-operation"/>  An expansion feature allowed more alphanumeric columns but certainly not over 50, as only ten words (five characters per word) were stored on the drum by a card read operation.{{Citation needed|date=October 2020}}<!-- I've no source for the expansion feature so can't really integrate with the other text.-->

[[File:IBM 650 with front open.jpg|thumb|IBM 650 at Texas A&M, opened up to show rear of front panel, vacuum tube modules and storage drum]]
[[File:RoehreIBM 090325.jpg|thumb|upright=0.6|Vacuum tube circuit module of type used in the 650]]
[[File:BronxScienceProgrammingClassroom1960.jpg|thumb|A classroom in 1960 at the [[Bronx High School of Science]] with IBM 650 instruction chart above blackboard, upper right]]

The base machine operation codes were:<ref>{{cite book|url=http://www.bitsavers.org/pdf/ibm/650/24-5002-0_BasicOpcodes.pdf|title=IBM 650 System Bulletin, Basic Operation Codes, Program Optimizing, Program Loading|year=1958|publisher=IBM}}</ref>

{| class="wikitable"

|-
|17
|AABL
|Add absolute to lower accumulator
|-
|15
|AL
|Add to lower accumulator
|-
|10
|AU
|Add to upper accumulator
|-
|45
|BRNZ
|Branch on accumulator non-zero
|-
|46
|BRMIN
|Branch on minus accumulator
|-
|44
|BRNZU
|Branch on non-zero in upper accumulator
|-
|47
|BROV
|Branch on overflow
|-
|90-99
|BRD
|Branch on 8 in distributor positions 1-10{{efn|Used to allow 533 control panel to signal CPU.}}
|-
|14
|DIV
|Divide
|-
|64
|DIVRU
|Divide and reset upper accumulator
|-
|69
|LD
|Load distributor
|-
|19
|MULT
|Multiply
|-
|00
|NO-OP
|No operation
|-
|71
|PCH
|Punch a card
|-
|70
|RD
|Read a card
|-
|67
|RAABL
|Reset accumulator and add absolute to lower accumulator
|-
|65
|RAL
|Reset accumulator and add to lower accumulator
|-
|60
|RAU
|Reset accumulator and add to upper accumulator
|-
|68
|RSABL
|Reset accumulator and subtract absolute from lower accumulator
|-
|66
|RSL
|Reset accumulator and subtract from lower accumulator
|-
|61
|RSU
|Reset accumulator and subtract from upper accumulator
|-
|35
|SLT
|Shift accumulator left
|-
|36
|SCT
|Shift accumulator left and count{{efn|Counts high-order zeros in upper accumulator.}}
|-
|30
|SRT
|Shift accumulator right
|-
|31
|SRD
|Shift accumulator right and round accumulator
|-
|01
|STOP
|Stop if console switch is set to stop, otherwise continue as a NO-OP
|-
|24
|STD
|Store distributor into memory
|-
|22
|STDA
|Store lower accumulator data address into distributor
Then store distributor into memory
|-
|23
|STIA
|Store lower accumulator instruction address into distributor
Then store distributor into memory
|-
|20
|STL
|Store lower accumulator into memory
|-
|21
|STU
|Store upper accumulator into memory.{{efn|Value stored takes sign of accumulator, except after a divide operation; then sign of remainder is stored.}}
|-
|18
|SABL
|Subtract absolute from lower accumulator
|-
|16
|SL
|Subtract from lower accumulator
|-
|11
|SU
|Subtract from upper accumulator
|-
|84
|TLU
|Table lookup
|}

{{notelist}}
Notes:

The IBM 653 options could implement additional instruction codes.<ref name=CPU-ext/>

==Sample program==

This one-card program, taken from the ''650 Programming Bulletin 5, IBM, 1956, 22-6314-0'', will set most of the drum storage to minus zeros. The program includes examples of instructions being executed from the console switches and from an accumulator.

To begin, a load card is keypunched with 80 consecutive digits (the second column below) so that, when read, drum locations 0001 through 0008 contents will be as shown.<ref>A 12 punch can be used to identify cards as ''load cards''.  Load cards are directly read into words 1-8 of the specified storage band</ref>

     0001 0000010000
     0002 0000000000-
     0003 1000018003
     0004 6100080007
     0005 2400008003
     0006 0100008000
     0007 6900060005
     0008 2019990003

The console digit switches (address 8000) are manually set to a Read instruction with data address 0004.

     loc-       op|data|next
     ation        |addr|instruction
                  |    |addr

     8000  RD   70 0004 xxxx  Read load card into first band read area

Each drum band has a read area; these read areas are in locations 0001-0010, 0051-0060, 0101-0110 and so on.  Any address in a band can be used to identify that band for a read instruction; the address 0004 identifies the first band.  Execution begins then, from the console with the reading of the eight words on the load card into locations 0001-0008 of the first memory band. In the case of reading a load card, the "next instruction address" is taken from the data address field, not the next instruction address field (shown above as xxxx).  Thus execution continues at 0004

     0004  RSU  61 0008 0007  Reset entire accumulator, subtract into upper (8003) the value 2019990003
     0007  LD   69 0006 0005  Load distributor with 0100008000
     0005  STD  24 0000 8003  Store distributor in location 0000, next instruction is in 8003 (the upper accumulator)
                              Note: the moving of data or instructions from one drum location to another
                                requires two instructions: LD, STD.

Now a two-instruction loop executes:

     8003  STL  20 1999 0003  Store lower accumulator (that accumulator was reset to 0- by the RSU instruction above)
                              The "1999" data address is decremented, below, on each iteration.
                              This instruction was placed in the upper accumulator by the RSU instruction above.
                              Note: this instruction, now in the upper accumulator, will be decremented and then
                                executed again while still in the accumulator.

     0003  AU   10 0001 8003  Decrement data address of the instruction in the accumulator by 1
                              (by adding 10000 to a negative number)

The STL's data address will, eventually, be decremented to 0003, and the AU ... instruction at 0003 will be overwritten with zeros.  When that occurs (the STL's next instruction address remains 0003) execution continues as follows:

     0003  NOOP 00 0000 0000  No-operation instruction, next instruction address is 0000
     0000  HALT 01 0000 8000  Halt, next instruction address is the console
                              (this Halt instruction was stored in 0000 by the STD instruction above)

==Software==
[[File:IBM 650 student program 1961.agr.jpg|thumb|Student program from 1961 written in IBM 650 machine language, based on an exercise in Andree's book<ref name=andree />]]
The 650 instruction set is simple enough that small programs could be written in machine language and this was common for student exercises.<ref name=andree>{{cite book | last = Andree | first = Richard V.
  | title = Programming the IBM 650 Magnetic Drum Computer and Data-Processing Machine
  | url = http://www.bitsavers.org/pdf/ibm/650/Andree_Programming_the_IBM_650_Magnetic_Drum_Computer_and_Data-Processing_Machine_1958.pdf
  | year = 1958}}</ref> There was a single-instruction-per-card format that could be loaded directly into the machine and executed. 

Machine language was awkward for large programs and, over time, a variety of programming languages and tools were 
written for the IBM 650. These included:

; Assemblers
*[[Symbolic Optimal Assembly Program]] (SOAP) — An [[assembler (computing)|assembler]]<ref name=soap>{{cite book
  | last = IBM
  | title = SOAP II for the IBM 650
  | year = 1957
  | url = http://www.bitsavers.org/pdf/ibm/650/24-4000-0_SOAPII.pdf
  | id = C24-4000-0
  }}</ref>
*Technical Assembly System (TASS) — A [[macro assembler]].

; Interpretive systems
* An Interpretive [[application virtual machine]] package originally published as "Complete Floating Decimal Interpretive System for the IBM 650 Magnetic Drum Calculator". This was known by several names:
** the Wolontis–Bell Labs Interpreter, the Bell System, the Bell interpreter, the Bell interpretive system,<ref name="Knuth1986">{{cite journal | first = Donald E. | last = Knuth
  | title = The IBM 650: An Appreciation from the Field
  | journal = IEEE Annals of the History of Computing
  | volume = 8 | issue = 1 | date = January–March 1986 | pages = 50–55
  | doi = 10.1109/MAHC.1986.10010
  | s2cid = 34595049
  }}
</ref> or BLIS — the Bell Lab Interpretive System<ref>{{cite book|url=http://www.bitsavers.org/pdf/ibm/650/28-4024_FltDecIntrpSys.pdf|title=IBM Reference Manual: Floating-Decimal Interpretive System for the IBM 650|publisher=IBM|year=1959|pages=63, xxi|id=28-4024|quote=This is a reprint of IBM 650 Technical Newsletter No. 11, March 1956, form 31-6822}}
.  This reference manual contains the following report, noting that ''In its external characteristics, the interpretive system described in this report owes much to the IBM Speedcoding System for the 701.'' {{cite book|title=Complete Floating Decimal Interpretive System for the IBM 650 Magnetic Drum Calculator|last=Wolontis|first=V.M.|publisher=Bell Laboratories, Inc, Murray Hill, New Jersey}}
<!--- I had written BLIS or BLISS even though I know BLIS to be correct.  Looking though the history of changes to this IBM 650 article I found --------------------
1) HOPL shows the name as BLISS, which is incorrect; the correct form is given in "Flow-Based Programming" - ISBN 0442017715"
2) Jpaulm (talk | contribs) . . (11,254 bytes) (-1) . . (→Software: BLIS is right - HOPL is wrong. I used it and it was definitely BLIS - see also discussion item 1 (it was apparently set correctly in 2006))
---------------------  so I've deleted the BLISS alternate I'd entered (see also the 2nd entry in the TALK page)
Just found this - the DEC BLISS language, probably the source of BLIS/BLISS confusion.
http://www.fh-jena.de/~kleine/history/languages/BlissLanguageGuide.pdf
 ---></ref>
** [[L1 and L2 (programming language)|L1 and (later) L2]]<ref>{{cite web |url=http://cm.bell-labs.com/cm/cs/cstr/99.html |archive-url=https://archive.today/20140902215751/http://cm.bell-labs.com/cm/cs/cstr/99.html |url-status=dead |archive-date=September 2, 2014 |title=Computing Science Technical Report No. 99 – A History of Computing Research at Bell Laboratories (1937–1975) |first1=Bernard D. |last1=Holbrook |first2=W. Stanley |last2=Brown |publisher=[[Bell Labs]] |access-date=August 27, 2020}}</ref><ref>{{cite web |url=http://bitsavers.org/pdf/ibm/650/34-6822-0_FltDecIntrpsys.pdf |title=A Complete Floating-Decimal Interpretive System For The IBM 650 Magnetic Drum Calculator |first=V. M. |last=Wolontis |publisher=IBM |location=US |via=bitsavers}}</ref> – known outside Bell Labs as "Bell 1" and "Bell 2", among other names (see above)
*Synthetic Programming System for Commercial Applications <ref>{{cite book |title=  650 Programming Bulletin 2 |publisher= IBM |year= 1956 |id= 22-6294-0 |pages= 40 |quote= The Interpretive routine described here is a fixed decimal three address system that provides for mathematical, logical, and input-output operations.  The logic for this system was obtained from the ''Complete Floating Decimal Interpretive System for the 650'' that was developed by the Bell Laboratories, Murray Hill, New Jersey.}}</ref>

; Algebraic languages / compilers
* Internal Translator (IT) — A compiler<ref>{{cite book
  | first1 = A.J.
  | last1 = Perlis
  | author-link1 = Alan Perlis
  | first2 = J.W.
  | last2 = Smith
  | first3 = H.R.
  | last3 = VanZoeren
  | title = Internal Translator; IT, A Compiler for the 650
  | date = 1958-04-18
  | url = http://www.bitsavers.org/pdf/ibm/650/CarnegieInternalTranslator.pdf
  | id = 650 Library Program 2.1.001
  }}</ref>
* Revised Unified New Compiler IT Basic Language Extended (RUNCIBLE) — An extension of IT at [[Case Institute of Technology|Case]]<ref>[[Donald Knuth]] published the [[flowchart]] of the compiler in 1959;{{Cite journal | last1 = Knuth | first1 = D. E. |author-link=Donald Knuth| doi = 10.1145/368481.368507 | title = RUNCIBLE—algebraic translation on a limited computer | journal = [[Communications of the ACM]]| volume = 2 | pages = 18–21| year = 1959 | issue = 11 | s2cid = 8224014 | doi-access = free }}; this was his first academic paper.</ref>
*[[FOR TRANSIT]] — A version of [[Fortran]] which compiled to IT which in turn was compiled to SOAP<ref>{{cite book
  | last = IBM
  | title = FOR TRANSIT Automatic Coding System for the IBM 650
  | year = 1959
  | url = http://www.bitsavers.org/pdf/ibm/650/28-4028_FOR_TRANSIT.pdf
  | id = 28-4028
  }}</ref>
*[[FORTRAN]]<ref>{{cite book
  | last = IBM
  | title = FORTRAN Automatic Coding System for the IBM 650
  | year = 1960
  | url = http://www.bitsavers.org/pdf/ibm/650/29-4047_FORTRAN.pdf
  | id = 29-4047
  }}</ref>

*GATE — A simple compiler with one character variable names
*[[Information Processing Language|IPL]] — The first list processing language. The best-known version was IPL-V.
*SPACE (Simplified Programming Anyone Can Enjoy) — A business-oriented two-step compiler through SOAP

==See also==
* [[Ferranti Mark 1]]
* [[History of IBM#1946–1959: Postwar]]
* [[IBM 700/7000 series]]
* [[Bull Gamma 3]], one of the main competitors to the IBM 650
* [[LEO (computer)]]
* [[List of vacuum-tube computers]]
* [[Short Code (computer language)|Short Code]]
* [[UNIVAC I]]
* [[UNIVAC Solid State]] announced by Sperry Rand in December 1958 as a response to the IBM 650. In June 1959, Remington Rand announced that it had written an IBM 650 emulator program to ease conversion.<ref>{{cite web |url=https://wiki.cc.gatech.edu/folklore/index.php/The_UNIVAC_Solid_State_Computer |title=The UNIVAC Solid State Computer |work=Unisys History Newsletter, Volume 1.2 December 1992 (revised 1999) |first=George |last=Gray |archive-url=https://web.archive.org/web/20160304194142/https://wiki.cc.gatech.edu/folklore/index.php/The_UNIVAC_Solid_State_Computer |archive-date=March 4, 2016}}</ref>

==Notes and references==
{{Reflist|30em}}

==Further reading==
*{{cite book | last = Andree | first = Richard V.
  | title = Programming the IBM 650 Magnetic Drum Computer and Data-Processing Machine
  | url = http://www.bitsavers.org/pdf/ibm/650/Andree_Programming_the_IBM_650_Magnetic_Drum_Computer_and_Data-Processing_Machine_1958.pdf
  | year = 1958}}
*{{cite book | last = IBM | title =IBM 650 Magnetic Drum Data-Processing Machine Manual of Operation.
  | url =http://www.bitsavers.org/pdf/ibm/650/22-6060-2_650_OperMan.pdf
  | year = 1955 | id =22-6060 }}
*{{cite book | last = IBM | title =IBM 650 Data-Processing System, Customer Engineering Manual of Instruction.
  | url =http://bitsavers.informatik.uni-stuttgart.de/pdf/ibm/650/22-6284-1_650_CE_Manual_of_Instruction.pdf
  | year = 1956 | id =22-6284-1 }}
*{{cite book | last = IBM | title = IBM Presents the 650 Magnetic Drum Data Processing Machine | url = http://archive.computerhistory.org/resources/text/IBM/IBM.650.1955.102646125.pdf | year = 1955 | id = 32-6770 | access-date = 2006-09-24 | archive-url = https://web.archive.org/web/20120205201824/http://archive.computerhistory.org/resources/text/IBM/IBM.650.1955.102646125.pdf | archive-date = 2012-02-05 | url-status = dead }}
*{{cite journal | first = Donald E. | last = Knuth
  | title = The IBM 650: An Appreciation from the Field
  | journal = IEEE Annals of the History of Computing
  | volume = 8 | issue = 1 | date = January–March 1986 | pages = 50–55
  | doi = 10.1109/MAHC.1986.10010
  | s2cid = 34595049
  | url = http://ed-thelen.org/comp-hist/KnuthIBM650Appreciation.pdf
  }}

==External links==
{{commons category}}
*[http://www.bitsavers.org/pdf/ibm/650/ Bitsavers.org: IBM 650 documents] (PDF files)
*[http://www.columbia.edu/acis/history/650.html Columbia University: The IBM 650 at Columbia University]
*{{webarchive|url=https://web.archive.org/web/20230712064404/https://www.ibm.com/ibm/history/ |date=2023-07-12 |title=IBM - Archives - Valuable resources on IBM's history - United States}}
*{{webarchive |url=https://web.archive.org/web/20230703155806/https://www.ibm.com/ibm/history/exhibits/650/650_intro.html |date=2023-07-03 |title=The IBM 650: Workhorse of Modern Industry}} Includes a chronology, technical specifications, photographs, representative customers, and applications the 650 was used for.
* [http://www.ed-thelen.org/comp-hist/HzG-VIDEO-Clip%20650.wmv Video clip of IBM 650 and RAMAC in operation], [http://www.ed-thelen.org/comp-hist/HzG-VIDEO-Clip-650-Trommel.wmv alternate version]
*{{cite book | first = Martin H. | last = Weik | title = A Third Survey of Domestic Electronic Digital Computing Systems
  | publisher = Ballistic Research Laboratories (BRL) | date =  March 1961 | id = Report No. 1115
  | url = http://ed-thelen.org/comp-hist/BRL61-ibm065.html#IBM-650-RAMAC }} Includes about 40 pages of IBM 650 survey detail: customers, applications, specifications, and costs.
*{{usurped|1=[https://web.archive.org/web/20230208105750/https://www.generationofcomputer.in/ibm-650-magnetic-drum-data-processing-machine/ IBM 650 “Magnetic Drum Data Processing Machine"]}}
<!------------------
* [http://sim650.googlecode.com An IBM 650 Simulator written in Python]
* [https://web.archive.org/web/20050109222002/http://www.mta.ca/~eruci/source.htm An IBM 650 assembler and Byte code interpreter - Written in Perl] at archive.org
* [http://www.mta.ca/~amiller/cs3711/cs3711_ibm650.html IBM 650 assembler and byte code interpreters]

These appear to be modern, student, implementations of 650 interpreters thus would not seem to be appropriate Wikipedia links/references.  Leaving this comment in text so as to, hopefully, avoid the 4th, 5th ...

-------------------->

{{IBM vacuum tube computers}}
{{Authority control}}

{{DEFAULTSORT:Ibm 650}}
[[Category:1950s computers]]
[[Category:IBM vacuum tube computers|650]]
[[Category:Computer-related introductions in 1954]]
[[Category:Decimal computers]]