View source for 4-bit

{{N-bit|4|}} A group of four bits is also called a [[Nibble|nibble]] and has 2<sup>4</sup> = 16 possible values.
Some of the first [[Engineering:Microprocessor|microprocessor]]s had a '''4-bit''' word length and were developed around 1970. The TMS 1000, the world's first single-[[Engineering:Integrated circuit|chip]] [[Engineering:Microprocessor|microprocessor]], was a 4-bit [[Central processing unit|CPU]]; it had a [[Harvard architecture]], with an on-chip instruction ROM, 8-bit-wide instructions and an on-chip data RAM with 4-bit words.<ref>{{cite book|url=http://blog.kevtris.org/blogfiles/TMS_1000_Data_Manual.pdf|title=TMS 1000 Series Data Manual|date=December 1976|publisher=[[Company:Texas Instruments|Texas Instruments]]|accessdate=July 20, 2013}}</ref> The first commercial microprocessor was the [[Binary-coded decimal|binary-coded decimal]] (BCD-based) [[Engineering:Intel 4004|Intel 4004]],<ref>{{cite web | title=The Microcomputer Revolution | first=Pamela E. | last=Mack | date=November 30, 2005 | url=http://www.clemson.edu/caah/history/FacultyPages/PamMack/lec122/micro.htm | accessdate=2009-12-23}}</ref><ref>{{cite journal | title=History in the Computing Curriculum | url=http://www.hofstra.edu/pdf/comphist_9812tla6.pdf | accessdate=2017-06-22 | journal= | archive-url=https://web.archive.org/web/20110719211222/http://www.hofstra.edu/pdf/CompHist_9812tla6.PDF | archive-date=2011-07-19 | dead-url=yes | df= }}</ref> developed for calculator applications in 1971; it had a 4-bit word length, but had 8-bit instructions and 12-bit addresses.

The [[HP Saturn]] processors, used in many [[Company:Hewlett-Packard|Hewlett-Packard]] calculators between 1984<!-- intro of HP-71B --> and 2003<!-- when the HP49 was discontinued and replaced by an ARM based model developed by Kinpo --> <!-- EOL announcement of HP 50g --> (including the HP&nbsp;48 series of scientific calculators) are "4-bit" (or hybrid 64-/4-bit) machines; as the Intel 4004 did, they string multiple 4-bit words together, e.g. to form a 20-bit memory address, and most of the registers are 64 bits wide, storing 16 4-bit digits.<!-- Its instructions were 10 bits wide.--><!-- The previous statement is factually inaccurate and not supported by the cited sources --><!-- <ref>{{cite web|url=http://www.hpmuseum.org/techcpu.htm|title=HP CPU and Programming|accessdate=January 14, 2014}}</ref> --><!-- This reference is invalid because it points to a page which describes the microarchitectures of the HP41 and older calculators which did not use the Saturn. The reference has been updated to point to the H.P. Saturn specific page. --><ref>{{cite web|url=http://www.hpmuseum.org/saturn.htm |title=The Saturn Processor |accessdate=December 23, 2015}}</ref><ref>{{cite web|url=http://grack.com/writings/hp48/GuidetotheSaturnProcessor.html|title=Guide to the Saturn Processor|accessdate=January 14, 2014}}</ref><ref>{{cite web|url=http://www.hpcalc.org/details.php?id=1693|title=Introduction to Saturn Assembly Language|accessdate=January 14, 2014}}</ref>

<!--{{Off-topic|date=December 2015|HP Saturn}}Since 2003, new Saturn-based HP calculators (including the HP 49/50 series) use a 32-bit processor with an ARM920T core to emulate an extended Saturn processor architecture named Saturn+ at a higher speed.
-->
The 4-bit processors were programmed in [[Assembly language|assembly language]] or [[Forth (programming language)|Forth]], e.g. "MARC4 Family of 4 bit Forth CPU"<ref>[http://www.ultratechnology.com/chips.htm Forth Chips].</ref> because of the extreme size constraint on programs and because common programming languages (for microcontrollers, 8-bit and larger), such as the [[C (programming language)|C programming language]], do not support 4-bit data types (C requires that the size of the [[Character (computing)#char|<code>char</code>]] data type be at least 8 bits,<ref>{{cite book
 | title=ISO/IEC 9899:1999 specification
 | at=p. 20, § 5.2.4.2.1
 | url=http://c0x.coding-guidelines.com/5.2.4.2.1.html
}}</ref> and that all data types other than bitfields have a size that is a multiple of the character size<ref>{{cite book
 | title=ISO/IEC 9899:1999 specification
 | at=p. 37, § 6.2.6.1 (4)
 | url=http://c0x.coding-guidelines.com/6.2.6.1.html 
}}</ref><ref>
Marshall Cline.
[http://www.parashift.com/c++-faq-lite/bytes-review.html "C++ FAQ: the rules about bytes, chars, and characters"].

The 1970s saw the emergence of 4-bit software applications for mass markets like pocket calculators. During the 1980s 4-bit microprocessor were used in handheld electronic games to keep costs low.

In the 1970s and 1980s, a number of research and commercial computers used [[Bit slicing|bit slicing]], in which the CPU's [[Arithmetic logic unit|arithmetic logic unit]] (ALU) was built from multiple 4-bit-wide sections, each section including a chip such as an Am2901 or [[Engineering:74181|74181]] chip.

The Zilog Z80, although it is an 8-bit microprocessor, has a 4-bit ALU.<ref>
Masatoshi Shima; Federico Faggin; Ralph Ungermann; Michael Slater.
[http://archive.computerhistory.org/resources/text/Oral_History/Zilog_Z80/102658073.05.01.pdf "Zilog Oral History Panel on the Founding of the Company and the Development of the Z80 Microprocessor"].
</ref><ref>
Ken Shirriff.
[http://www.righto.com/2013/09/the-z-80-has-4-bit-alu-heres-how-it.html "The Z-80 has a 4-bit ALU"].
</ref>

==Modern uses==
While 32- and 64-bit processors are more prominent in modern consumer electronics, 4-bit CPUs continue to be used (usually as part of a [[Engineering:Microcontroller|microcontroller]]) in cost-sensitive applications that require minimal computing power.  For example, one bicycle computer specifies that it uses a "4-bit 1-chip microcomputer".<ref>{{cite web|url=http://cateye.com/images/manual/CC-COM10W_ENG_v3.pdf|title=Cateye Commuter Manual|accessdate=February 11, 2014}}</ref><!--"Products(0)", only this document found from 2005-->  Other typical uses include [[Engineering:Coffeemaker|coffee makers]], [[Engineering:Remote control|infrared remote controls]],<ref name="RenesasPD67">[http://documentation.renesas.com/doc/DocumentServer/U14935EJ2V1DS00.pdf μPD67, 67A, 68, 68A, 69 4-bit single-chip microcontroller for infrared remote control transmission]</ref> and [[Engineering:Security alarm|security alarm]]s.<ref>{{cite web |url=http://cse.secs.oakland.edu/haskell/CSE171/Lectures/Fall2004/L12.2%20Microcontrollers.ppt |last=Haskell |first=Richard |title=Introduction to Digital Logic and Microprocessors (Lecture 12.2) |accessdate=February 11, 2014}}</ref><!--4-bit" or "4 bit" isn't actually in the source, 8-bit PIC is, and "Includes coffee makers, burglar alarms, TV remote controls, simple robots, etc…"-->

Use of 4-bit processors has declined relative to 8-bit or even 32-bit processors, as they are hard to find cheaper in general computer suppliers' stores. The simplest kinds are not available in any of them, and others are "non-stock" and more expensive.<ref>{{cite web|url=http://www.digikey.com/product-search/en/integrated-circuits-ics/embedded-microcontrollers/2556109?k=4-bit|title=Embedded - Microcontrollers - Integrated Circuits (ICs) - DigiKey|author=|date=|website=www.digikey.com|accessdate=9 April 2018}}</ref> (A few expensive ones can be found, {{as of|2014|lc=y}}, on eBay.)<ref>{{cite web|url=http://www.ebay.com/itm/Toshiba-TMP47C1637N-4bit-MCU-microcontroller-skinny-DIP42-/111294657595?pt=LH_DefaultDomain_0&hash=item19e9adb43b|title=Other Integrated Circuits - eBay|author=|date=|website=eBay|accessdate=9 April 2018}}</ref><ref>{{cite web|url=http://www.ebay.com/itm/Motorola-IC-MC14500B-MC14500BCL-100-NEW-/320837692605|title=Motorola IC MC14500B / MC14500BCL ( 100% NEW )  - eBay|author=|date=|website=eBay|accessdate=9 April 2018}}</ref><ref>{{cite web|url=http://www.ebay.com/itm/KL1868VE1-Soviet-CMOS-Clone-Matsushita-MN15500-4bit-MCU-/400212898610?pt=US_Vintage_Computers_Mainframes&hash=item5d2e8c3332|title=KL1868VE1 Soviet CMOS Clone Matsushita MN15500 4bit MCU  - eBay|author=|date=|website=eBay|accessdate=9 April 2018}}</ref>

Electronics stores still carry, {{as of|2014|lc=y}}, non-CPU/non-[[Engineering:Microcontroller|MCU]] 4-bit chips, such as counters.

{{As of|2015}}, most PC motherboards, especially laptop motherboards, use a 4-bit LPC bus (introduced in 1998) to connect the southbridge to the motherboard firmware flash ROM (UEFI or [[BIOS]]) and the Super I/O chip.<ref>
Scott Mueller.
[https://books.google.com/books?id=xCXVGneKwScC "Upgrading and Repairing Laptops"].
2004.
p. 176.
</ref><ref>
David S. Lawyer.
[http://www.tldp.org/HOWTO/Plug-and-Play-HOWTO-6.html#lpc_ "Plug-and-Play-HOWTO: LPC Bus"]
2007.
</ref>

==Details==
{{Main|Nibble}}

With 4 bits, it is possible to create 16 different values. All single-digit [[Hexadecimal|hexadecimal]] numbers can be written with four bits. [[Binary-coded decimal]] is a digital encoding method for numbers using decimal notation, with each decimal digit represented by four bits.

{| class="wikitable"
|-
! Binary !! [[Octal]] !! [[Decimal]] !! [[Hexadecimal]]
|-
| 0000
| 0
| 0
| 0
|-
| 0001
| 1
| 1
| 1
|-
| 0010
| 2
| 2
| 2
|-
| 0011
| 3
| 3
| 3
|-
| 0100
| 4
| 4
| 4
|-
| 0101
| 5
| 5
| 5
|-
| 0110
| 6
| 6
| 6
|-
| 0111
| 7
| 7
| 7
|-
| 1000
| 10
| 8
| 8
|-
| 1001
| 11
| 9
| 9
|-
| 1010
| 12
| 10
| A
|-
| 1011
| 13
| 11
| B
|-
| 1100
| 14
| 12
| C
|-
| 1101
| 15
| 13
| D
|-
| 1110
| 16
| 14
| E
|-
| 1111
| 17
| 15
| F
|}

==List of 4-bit processors==
[[File:Intel C4004 greytraces CPU.jpg |thumb|alt=16-pin DIP| Intel C4004]]
[[File:Alps remote control BHR970001B-7517.jpg |thumb|alt=infrared remote control PCB| an infrared remote control transmitter controlled by a NEC D63GS 4-bit microcontroller]]
[[File:Alps remote control BHR970001B - NEC D63GS-7525.jpg |thumb|alt=20-pin PSOP|NEC D63GS: a 4-bit microcontroller for infrared remote control transmission]]
[[File:Olympia CD700 Desktop Calculator. 1971.Microprogrammable Arithmetic Processor System Devices (MAPS).jpg |thumb|alt=card-edge PCB| Olympia CD700 Desktop Calculator using the National Semiconductor MAPS MM570X bit-serial 4-bit microcontroller]]
[[File:National Semiconductor MM5700CA D Microprocessor.jpg |thumb|alt=16-pin DIP| National Semiconductor MM5700CA/D bit-serial 4-bit microcontroller ]]

* TMS 1000
* [[Engineering:Intel 4004|Intel 4004]]
* Intel 4040
* 10NES
* Atmel MARC4 core<ref>{{cite web|url=http://www.atmel.com/Images/doc4747.pdf |archiveurl=https://web.archive.org/web/20141215021454/http://www.atmel.com/Images/doc4747.pdf |archivedate=2014-12-15 |title=MARC4 4-bit Microcontrollers - Programmer's Guide|publisher=Atmel|accessdate=January 14, 2014}}</ref><ref>{{cite web|url=http://www.atmel.com/products/MARC4/|title=MARC4 4-Bit Architecture|publisher=Atmel|archiveurl=https://web.archive.org/web/20090531214448/http://atmel.com/products/MARC4/|archivedate=May 31, 2009}}</ref> – (discontinued: "Last ship date: March 7, 2015"<ref>{{cite web|url=http://www.atmel.com/images/he140901.pdf|title=Product End-of-Life (EOL) Notification|date=March 7, 2014|website=Atmel|archive-url=https://web.archive.org/web/20160807174435/http://www.atmel.com/images/he140901.pdf|archive-date=August 7, 2016}}</ref>)
* [[Company:Samsung|Samsung]] S3C7 (KS57 Series) 4-bit microcontrollers (RAM: 512 to 5264 nibbles, 6&nbsp;MHz clock)
* [[Company:Toshiba|Toshiba]] TLCS-47 series
* [[HP Saturn]]<!-- and Saturn+ series --> <!-- The HP "Saturn+" is not a real microprocessor but instead a Saturn emulator running on an ARM microprocessor -->
* [[Company:NEC|NEC]] μPD75X
* NEC [[Engineering:ΜCOM-4|μCOM-4]]
* NEC (now Renesas) µPD612xA (discontinued), µPD613x, μPD6x<ref name="RenesasPD67" /><ref>[http://documentation.renesas.com/doc/DocumentServer/U15144EJ1V1DS00.pdf μPD6P9 4-bit single-chip microcontroller for infrared remote control transmission]</ref> and μPD1724x<ref>[http://documentation.renesas.com/doc/DocumentServer/U15002EJ1V1DS00.pdf μPD17240, 17241, 17242, 17243, 17244, 17245, 17246 4-bit single-chip microcontrollers for small general-purpose infrared remote control transmitters]</ref> infrared remote control transmitter microcontrollers<ref>[http://documentation.renesas.com/doc/DocumentServer/U14372EJ5V0PF00.pdf Microcontrollers for Remote Controllers]</ref><ref>{{cite web|url=http://www.necel.com/micro/en/product/mr_48_remocon.html |title=Mask ROM/ROMless Products 4/8bit Remote Control  |deadurl=yes |archiveurl=https://web.archive.org/web/20081028181219/http://www.necel.com/micro/en/product/mr_48_remocon.html |archivedate=October 28, 2008 }}</ref>
* EM Microelectronic-Marin EM6600 family,<ref>
Robert Cravotta.
[http://www.embeddedinsights.com/directory/epd-downloads.php "Embedded Processing Directory"]
</ref> EM6580,<ref>{{Cite web |url=http://www.emmarin.com/Products.asp?IdProduct=215 |title=EM6580 |access-date=2013-05-12 |archive-url=https://web.archive.org/web/20131219221418/http://www.emmarin.com/Products.asp?IdProduct=215 |archive-date=2013-12-19 |dead-url=yes |df= }}</ref><ref>
[http://www.emmicroelectronic.com/products/microcontrollers/multi-io/em6580 "EM6580 low power Flash 4-bit microcontroller"]
</ref> EM6682,<ref>
[http://www.emmicroelectronic.com/products/microcontrollers/multi-io/em6682 "EM6682"]
</ref> etc.
* Epson S1C63 family
* National Semiconductor MAPS MM570X

==See also==
* [[Engineering:GMC-4|GMC-4]]
* [[Engineering:Low Pin Count|Low Pin Count]]

==References==
{{Reflist}}

==External links==
* [http://www.hpmuseum.org/saturn.htm Saturn CPU]
* {{cite web |url=http://www.epson.jp/device/semicon_e/product/mcu/high_4bit/ |archiveurl=https://web.archive.org/web/20130729191831/http://www.epson.jp/device/semicon_e/product/mcu/high_4bit/ |archivedate=2013-07-29 |website=Epson |title=Products: High Performance 4-bit Microcontrollers [ S1C63 family ]}}
* [http://www.embeddedinsights.com/channels/2010/12/10/considerations-for-4-bit-processing/ Considerations for 4-bit processing]

{{CPU technologies}}

[[Category:Data unit]]

{{Sourceattribution|4-bit|1}}