In computer architecture, 24-bit integers, memory addresses, or other data units are those that are 24 bits (3 octets) wide. Also, 24-bit CPU and ALU architectures are those that are based on registers, address buses, or data buses of that size.
The term SWORD is sometimes used to describe a 24-bit data type with the S prefix referring to sesqui.
The IBM System/360, announced in 1964, was a popular computer system with 24-bit addressing and 32-bit general registers and arithmetic. The early 1980s saw the first popular personal computers, including the IBM PC/AT with an Intel 80286 processor using 24-bit addressing and 16-bit general registers and arithmetic, and the Apple Macintosh 128K with a Motorola 68000 processor featuring 24-bit addressing and 32-bit registers.
The range of unsigned integers that can be represented in 24 bits is 0 to 16,777,215 (FFFFFF16 in hexadecimal). The range of signed integers that can be represented in 24 bits is −8,388,608 to 8,388,607.
Several fixed-point digital signal processors have a 24-bit data bus, selected as the basic word length because it gave the system a reasonable precision for the processing audio (sound). In particular, the Motorola 56000 series has three parallel 24-bit data buses, one connected to each memory space: program memory, data memory X, and data memory Y.
Engineering Research Associates (later merged into UNIVAC) designed a series of 24-bit drum memory machines including the Atlas, its commercial version the UNIVAC 1101, the ATHENA computer, the UNIVAC 1824 guidance computer, etc. Those designers selected a 24-bit word length because the Earth is roughly 40 million feet in diameter, and an intercontinental ballistic missile guidance computer needs to do the Earth-centered inertial navigation calculations to an accuracy of a few feet.