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In computing, an arithmetic logic unit (ALU) is a combinational digital circuit that performs arithmetic and bitwise operations on integer binary numbers. [ 1 ] [ 2 ] This is in contrast to a floating-point unit (FPU), which operates on floating point numbers.
The 74181 is a 4-bit slice arithmetic logic unit (ALU), implemented as a 7400 series TTL integrated circuit. Introduced by Texas Instruments in February 1970, [1] it was the first complete ALU on a single chip. [2] It was used as the arithmetic/logic core in the CPUs of many historically significant minicomputers and other devices.
The arithmetic logic unit (ALU) is a digital circuit within the processor that performs integer arithmetic and bitwise logic operations. The inputs to the ALU are the data words to be operated on (called operands ), status information from previous operations, and a code from the control unit indicating which operation to perform.
In many computers and other kinds of processors, adders are used in the arithmetic logic units (ALUs). They are also used in other parts of the processor, where they are used to calculate addresses , table indices , increment and decrement operators and similar operations.
Adders are a part of the core of an arithmetic logic unit (ALU). The control unit decides which operations an ALU should perform (based on the op code being executed) and sets the ALU operation. The D input to the adder–subtractor above would be one such control line from the control unit.
In a computer's central processing unit (CPU), the accumulator is a register in which intermediate arithmetic logic unit results are stored.. Without a register like an accumulator, it would be necessary to write the result of each calculation (addition, multiplication, shift, etc.) to cache or main memory, perhaps only to be read right back again for use in the next operation.
In the 1970s and 1980s, a number of research and commercial computers used bit slicing, in which the CPU's arithmetic logic unit (ALU) was built from multiple 4-bit-wide sections, each section including a chip such as an Am2901 or 74181. The Zilog Z80, although it is an 8-bit microprocessor, has a 4-bit ALU. [11] [12]
4-bit arithmetic logic unit/function generator, generate and propagate outputs 20 SN74LS381A: 74x382 1 4-bit arithmetic logic unit/function generator, ripple carry and overflow outputs 20 SN74LS382: 74x383 1 8-bit register open-collector 20 SN74S383: 74x384 1 8-bit by 1-bit two's complement multipliers 16 SN74LS384: 74x385 4 quad serial adder ...