74181

The 74181 is a 4-bit binary arithmetic logic unit (ALU) integrated circuit manufactured by Texas Instruments. It was a significant component in early minicomputers and microcomputers, providing the fundamental logic for performing arithmetic and Boolean operations. Released in the 1970s, it was a popular choice for designers due to its versatility and the ability to perform 16 different arithmetic and logic functions.

The 74181 has two 4-bit inputs, A and B, and a 1-bit carry-in input, Cn. It produces a 4-bit output, F, and a carry-out output, Cn+4. The specific function performed is determined by a set of four mode-select inputs (S0-S3) and two operation-select inputs (M). For example, by setting the mode-select inputs, the chip can be configured to perform addition, subtraction, logical AND, OR, XOR, and other operations.

The ALU's ability to handle both arithmetic and logical operations made it a cornerstone of early digital processor design. Multiple 74181 chips could be cascaded together to create wider ALUs, allowing for the processing of larger numbers. Its widespread use contributed to the development of more powerful and complex computing systems during its era, before being superseded by more integrated and capable microprocessors.