# 4-bit computing

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Computer architecture bit width

Computer architecture bit widths Bit 1 4 8 12 16 18 24 26 30 31 32 36 45 48 60 64 128 256 512 bit slicing Application 8 16 32 64 Binary floating-point precision 16 (×½) 24 32 (×1) 40 64 (×2) 80 128 (×4) 256 (×8) Decimal floating-point precision 32 64 128 v t e

**4-bit computing** is the use of [computer architectures](/source/Computer_architecture) in which [integers](/source/Integer_(computer_science)) and other [data](/source/Data_(computer_science)) units are 4 [bits](/source/Bit) wide. 4-bit [central processing unit](/source/Central_processing_unit) (CPU) and [arithmetic logic unit](/source/Arithmetic_logic_unit) (ALU) architectures are those that are based on [registers](/source/Processor_register) or [data buses](/source/Bus_(computing)) of that size. A group of four bits is also called a [nibble](/source/Nibble) and has 24 = 16 possible values, with a range of 0 to 15.

4-bit computation is largely obsolete, i.e. CPUs supporting 4-bit as the maximum size, or 4-bit data bus are no longer available, but 4-bit microcontrollers, such as the [EM Microelectronic](/source/EM_Microelectronic) EM6580, are still available as of 2026[\[update\]](https://en.wikipedia.org/w/index.php?title=4-bit_computing&action=edit).[1]

4-bit processors were widely used in [electronic calculators](/source/Electronic_calculator) and other roles where decimal math was used, like electronic [cash registers](/source/Cash_register), [microwave oven](/source/Microwave_oven) timers, and so forth. This is because a 4-bit value holds a single [binary-coded decimal](/source/Binary-coded_decimal) (BCD) digit, making it a natural size for directly processing decimal values. As a 4-bit value is generally too small to hold a [memory address](/source/Memory_address) for real-world programs or data, the [address bus](/source/Address_bus) of these systems was generally larger. For instance, the canonical 4-bit [microprocessor](/source/Microprocessor), the [Intel 4004](/source/Intel_4004), had a 12-bit address format.

4-bit designs were used only for a short period when [integrated circuits](/source/Integrated_circuit) were still expensive, and were found primarily in cost-sensitive roles. While 4-bit computing is mostly obsolete, 4-bit values are still used in the same decimal-centric roles they were developed for, and modern implementations are generally much wider and process multiple 4-bit values in parallel. By the 1990s, most such uses had been replaced by general purpose binary designs.

## History

20-pin PSOP – NEC D63GS: a 4-bit microcontroller for [infrared remote control](/source/Infrared_remote_control) transmission

16-pin DIP – Intel C4004

Olympia CD700 Desktop Calculator using the National Semiconductor MAPS MM570X [bit-serial](/source/Bit-serial) 4-bit microcontroller

Infrared remote control PCB – an [infrared remote control](/source/Infrared_remote_control) transmitter controlled by a NEC D63GS 4-bit microcontroller

A 4-bit processor may seem limited, but it is a good match for calculators, where each decimal digit fits into four bits.[2]

Some of the first [microprocessors](/source/Microprocessor) had a 4-bit word length and were developed around 1970. The first commercial microprocessor was the [binary-coded decimal](/source/Binary-coded_decimal) (BCD-based) [Intel 4004](/source/Intel_4004),[3][4] developed for calculator applications in 1971; it had a 4-bit word length, but had 8-bit instructions and 12-bit addresses. It was succeeded by the [Intel 4040](/source/Intel_4040), which added [interrupt](/source/Interrupt) support and a variety of other new features.

The first commercial single-chip computer was the 4-bit [Texas Instruments](/source/Texas_Instruments) [TMS 1000](/source/TMS_1000) (1974).[2] It contained a 4-bit [CPU](/source/Central_processing_unit) with a [Harvard architecture](/source/Harvard_architecture) and 8-bit-wide instructions, an on-chip instruction ROM, and an on-chip data RAM with 4-bit words.[5]

The [Rockwell PPS-4](/source/Rockwell_PPS-4) was another early 4-bit processor, introduced in 1972, which had a long lifetime in handheld games and similar roles. It was steadily improved and by 1975 been combined with several support chips to make a one-chip computer.[6]

The 4-bit processors were programmed in [assembly language](/source/Assembly_language) or [Forth](/source/Forth_(programming_language)), e.g. "MARC4 Family of 4 bit Forth CPU"[7] (which is now discontinued) because of the extreme size constraint on programs and because common programming languages (for [microcontrollers](/source/Microcontroller), 8-bit and larger), such as the [C programming language](/source/C_(programming_language)), do not support 4-bit data types (C, and [C++](/source/C%2B%2B), and more languages require that the size of the [char](/source/Character_(computing)#char) data type be at least 8 bits,[8] and that all data types other than bitfields have a size that is a multiple of the character size[9][10][11]).

The 1970s saw the emergence of 4-bit software applications for mass markets like pocket calculators. During the 1980s, 4-bit microprocessors were used in [handheld electronic games](/source/Handheld_electronic_game) to keep costs low.

In the 1970s and 1980s, a number of research and commercial computers used [bit slicing](/source/Bit_slicing), in which the CPU's [arithmetic logic unit](/source/Arithmetic_logic_unit) (ALU) was built from multiple 4-bit-wide sections, each section including a chip such as an [Am2901](/source/AMD_Am2900) or [74181](/source/74181).

The [Zilog Z80](/source/Zilog_Z80) (discontinued in 2024), although it is an 8-bit microprocessor, has a 4-bit ALU.[12][13]

Although the [Data General Nova](/source/Data_General_Nova) is a series of 16-bit minicomputers, the original Nova and the Nova 1200 internally processed numbers 4 bits at a time with a 4-bit ALU,[14] sometimes called "nybble-serial".[15]

The [HP Saturn](/source/HP_Saturn) processors, used in many [Hewlett-Packard](/source/Hewlett-Packard) calculators between 1984 and 2003 (including the [HP 48 series](/source/HP_48_series) of scientific calculators) are "4-bit" (or hybrid 64-/4-bit) machines. 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. Operations were performed nybble-serial.[16][17][18]

In addition, some early calculators – such as the 1967 [Casio AL-1000](https://en.wikipedia.org/w/index.php?title=Casio_AL-1000&action=edit&redlink=1), the 1972 [Sinclair Executive](/source/Sinclair_Executive), and the aforementioned 1984 [HP Saturn](/source/HP_Saturn) – had 4-bit [datapaths](/source/Datapath) that accessed their registers 4 bits (one BCD digit) at a time.[19]

## Uses

National Semiconductor COP410L, a low-end 4-bit microcontroller. 512 bytes of ROM in upper left corner, 128 bits of RAM in upper right corner. Click to zoom.

One bicycle computer specifies that it uses a "4 bit, 1-chip microcomputer".[20] Other typical uses include [coffee makers](/source/Coffeemaker), [infrared remote controls](/source/Remote_control),[21] and [security alarms](/source/Security_alarm).[22]

The processor in Barbie typewriters that can encrypt is a 4-bit microcontroller.[23]

Several manufacturers used 4-bit microcontrollers in their early electronic games:[24]

- [Mattel's](/source/Mattel) Funtronics Jacks, Red Light Green Light, Tag, Plus One and Dalla$.

- [Milton Bradley](/source/Milton_Bradley_Company) Lightfight and Electronic Battleship 1982.

- [Coleco](/source/Coleco) Head to Head Basketball.

- National Semiconductor Quiz Kid Racer.

- [Entex](/source/Entex_Industries) Space Invader.

- [Texas Instruments](/source/Texas_Instruments) My Little Computer.[25]

Western Digital used a 4-bit microcontroller as the basis for their WD2412 time-of-day clock.[26]

The [Grundy Newbrain](/source/Grundy_Newbrain) computer uses a 4-bit microcontroller to manage its keyboard, tape I/O, and its built-in 16 character [VF](/source/Vacuum_fluorescent_display) alphanumeric display.[27]

The [Apple Lisa](/source/Apple_Lisa) utilizes a 4-bit microcontroller to control the keyboard, mouse, RTC, and soft power switch.[28]

## Details

Main article: [Nibble](/source/Nibble)

With 4 bits, it is possible to create 16 different values. All single-digit [hexadecimal](/source/Hexadecimal) numbers can be written with four bits.

[Binary-coded decimal](/source/Binary-coded_decimal) is a digital encoding method for numbers using decimal notation, with each decimal digit represented by four bits.

## List of 4-bit processors

National Semiconductor MM5700CA/D [bit-serial](/source/Bit-serial) 4-bit microcontroller

- [Intel 4004](/source/Intel_4004) (first 4-bit microprocessor and widely regarded as the first commercially available microprocessor from 1971, discontinued 1981)

- [Intel 4040](/source/Intel_4040) (discontinued 1981)

- [TMS 1000](/source/TMS_1000) (the first high-volume commercial microcontroller, from 1974, after Intel 4004; now discontinued)

- [American Microsystems S2000](/source/American_Microsystems_S2000)

- [Atmel](/source/Atmel) MARC4 core[29][30] (discontinued because of low demand. Last ship date: 7 March 2015[31])

- [Essex SX 200](/source/Essex_SX_200)

- [Samsung](/source/Samsung) S3C7 (KS57 Series) 4-bit microcontrollers (RAM: 512 to 5264 nibbles, 6 MHz clock)

- [Toshiba](/source/Toshiba) [TLCS-47](/source/TLCS-47) series

- [HP Saturn](/source/HP_Saturn)

- [NEC](/source/NEC) [μPD75X](/source/%CE%9CPD75X)

- NEC [μCOM-4](/source/%CE%9CCOM-4)

- NEC (now [Renesas](/source/Renesas)) μPD612xA (discontinued), μPD613x, [μPD6x](/source/%CE%9CPD6x)[21][32] and [μPD1724x](/source/%CE%9CPD1724x)[33] infrared remote control transmitter microcontrollers[34][35]

- [EM Microelectronic-Marin](/source/EM_Microelectronic-Marin) EM6600 family,[36] EM6580,[37][38] EM6682,[39] etc.

- Epson [S1C63](/source/S1C63) family

- [National Semiconductor](/source/National_Semiconductor) "COPS I" and "COPS II" ("[COP400](/source/COP400)") 4-bit microcontroller families[40]

- [National Semiconductor](/source/National_Semiconductor) MAPS MM570X

- [Rockwell PPS-4](/source/Rockwell_PPS-4)

- [Sharp](/source/Sharp_Electronics) SM590/SM591/SM595[41]: 26–34

- Sharp SM550/SM551/SM552[41]: 36–48

- Sharp SM578/SM579[41]: 49–64

- Sharp SM5E4[41]: 65–74

- Sharp LU5E4POP[41]: 75–82

- Sharp SM5J5/SM5J6[41]: 83–99

- Sharp SM530[41]: 100–109

- Sharp SM531[41]: 110–118

- Sharp SM500[41]: 119–127 (ROM 1197×8 bit, RAM 40×4 bit, a divider and 56-segment LCD driver circuit)

- Sharp SM5K1[41]: 128–140

- Sharp SM4A[41]: 141–148

- Sharp SM510[41]: 149–158 (ROM 2772×8 bit, RAM 128×4 bit, a divider and 132-segment LCD driver circuit)

- Sharp SM511/SM512[41]: 159–171 (ROM 4032×8 bit, RAM 128/142×4 bit, a divider and 136/200-segment LCD driver circuit)

- Sharp SM563[41]: 172–186

## See also

- [GMC-4](/source/GMC-4)

- [Hitachi HD44780 LCD controller](/source/Hitachi_HD44780_LCD_controller)

- Intel's [LPC](/source/Low_Pin_Count) (low-pin-count) bus/interface for 4-bit communication - Its successor for modern computers, Intel's [Enhanced Serial Peripheral Interface](/source/Enhanced_Serial_Peripheral_Interface) (eSPI), allows 1-bit, 2-bit, and 4-bit communication

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## External links

- [Saturn CPU](http://www.hpmuseum.org/saturn.htm)

- ["Products: High Performance 4-bit Microcontrollers (S1C63 family)"](https://web.archive.org/web/20130729191831/http://www.epson.jp/device/semicon_e/product/mcu/high_4bit/). *Epson*. Archived from [the original](http://www.epson.jp/device/semicon_e/product/mcu/high_4bit/) on 2013-07-29.

- [Considerations for 4-bit processing](http://www.embeddedinsights.com/channels/2010/12/10/considerations-for-4-bit-processing/)

v t e Processor technologies Models Abstract machine Stored-program computer Finite-state machine with datapath Hierarchical Deterministic finite automaton Queue automaton Cellular automaton Quantum cellular automaton Turing machine Alternating Turing machine Universal Post–Turing Quantum Nondeterministic Turing machine Probabilistic Turing machine Hypercomputation Zeno machine Belt machine Stack machine Register machines Counter Pointer Random-access Random-access stored program Architecture Microarchitecture Von Neumann Harvard modified Dataflow Transport-triggered Cellular Endianness Memory access NUMA HUMA Load–store Register/memory Cache hierarchy Memory hierarchy Virtual memory Secondary storage Heterogeneous Fabric Multiprocessing Cognitive Neuromorphic Instruction set architectures Types Orthogonal instruction set CISC RISC Application-specific EDGE TRIPS VLIW EPIC MISC OISC NISC ZISC VISC architecture Quantum computing Comparison Addressing modes Instruction sets Motorola 68000 series VAX PDP-11 x86 ARM Stanford MIPS MIPS MIPS-X Power POWER PowerPC Power ISA Clipper architecture SPARC SuperH DEC Alpha ETRAX CRIS M32R Unicore Itanium OpenRISC RISC-V MicroBlaze LMC System/3x0 S/360 S/370 S/390 z/Architecture Tilera ISA VISC architecture Epiphany architecture Others Execution Instruction pipelining Pipeline stall Operand forwarding Classic RISC pipeline Hazards Data dependency Structural Control False sharing Out-of-order Scoreboarding Tomasulo's algorithm Reservation station Re-order buffer Register renaming Wide-issue Speculative Branch prediction Memory dependence prediction Parallelism Level Bit Bit-serial Word Instruction Pipelining Scalar Superscalar Task Thread Process Data Vector Memory Distributed Multithreading Temporal Simultaneous Hyperthreading Simultaneous and heterogenous Speculative Preemptive Cooperative Flynn's taxonomy SISD SIMD Array processing (SIMT) Pipelined processing Associative processing SWAR MISD MIMD SPMD Processor performance Transistor count Instructions per cycle (IPC) Cycles per instruction (CPI) Instructions per second (IPS) Floating-point operations per second (FLOPS) Transactions per second (TPS) Synaptic updates per second (SUPS) Performance per watt (PPW) Cache performance metrics Computer performance by orders of magnitude Types Central processing unit (CPU) Graphics processing unit (GPU) GPGPU Vector Barrel Stream Tile processor Coprocessor PAL ASIC FPGA FPOA CPLD Multi-chip module (MCM) System in a package (SiP) Package on a package (PoP) By application Embedded system Microprocessor Microcontroller Mobile Ultra-low-voltage ASIP Soft microprocessor Systems on chip System on a chip (SoC) Multiprocessor (MPSoC) Cypress PSoC Network on a chip (NoC) Hardware accelerators Coprocessor AI accelerator Graphics processing unit (GPU) Image processor Vision processing unit (VPU) Physics processing unit (PPU) Digital signal processor (DSP) Tensor Processing Unit (TPU) Secure cryptoprocessor Network processor Baseband processor Word size 1-bit 4-bit 8-bit 12-bit 15-bit 16-bit 24-bit 32-bit 48-bit 64-bit 128-bit 256-bit 512-bit bit slicing others variable Core count Single-core Multi-core Manycore Heterogeneous architecture Components Core Cache CPU cache Scratchpad memory Data cache Instruction cache replacement policies coherence Bus Clock rate Clock signal FIFO Functional units Arithmetic logic unit (ALU) Address generation unit (AGU) Floating-point unit (FPU) Memory management unit (MMU) Load–store unit Translation lookaside buffer (TLB) Branch predictor Branch target predictor Integrated memory controller (IMC) Memory management unit Instruction decoder Logic Combinational Sequential Glue Logic gate Quantum Array Registers Processor register Status register Stack register Register file Memory buffer Memory address register Program counter Control unit Hardwired control unit Instruction unit Data buffer Write buffer Microcode ROM Counter Datapath Multiplexer Demultiplexer Adder Multiplier CPU Binary decoder Address decoder Sum-addressed decoder Barrel shifter Circuitry Integrated circuit 3D Mixed-signal Power management Boolean Digital Analog Quantum Switch Power management PMU APM ACPI Dynamic frequency scaling Dynamic voltage scaling Clock gating Performance per watt (PPW) Related History of general-purpose CPUs Microprocessor chronology Processor design Digital electronics Hardware security module Semiconductor device fabrication Tick–tock model Pin grid array Chip carrier

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Adapted from the Wikipedia article [4-bit computing](https://en.wikipedia.org/wiki/4-bit_computing) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/4-bit_computing?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.