4-bit computing

In computer architecture, 4-bit integers, memory addresses, or other data units are those that are 4 bits wide. Also, 4-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers, address buses, or data buses of that size. The Intel 4004, the world's first commercially available single-chip microprocessor, was a 4-bit CPU. (The F14 CADC was created a year before the 4004, but its existence was classified.) Also, the HP48 Saturn processor (a commonly used scientific calculator) is basically a 4-bit machine, though it strings multiple words together, e.g. its 20-bit memory addressing.

The 1970s saw the emergence of 4-bit software applications for mass markets like pocket calculators.

With 4 bits, it is possible to create 16 different values. All of the hexadecimal numbers can be written with 4 bits.

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

Intel CPUs

• Intel 4004
• Intel 4040

Atmel Microcontrollers

• Atmel MARC4 core

External references

• Saturn CPU link