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# What is the full form of ALU?

**Full form of ALU**: Here, we are going to learn **what does ALU stands for?** **ALU** – which is an abbreviation of **"Arithmetic Logic Unit"** in Computer Acronyms/Abbreviations, etc.

Submitted by Anushree Goswami, on March 26, 2020

## ALU: Arithmetic Logic Unit

**ALU is an abbreviation of the "Arithmetic Logic Unit"**.

It is a merged form of a digital electronic circuit that carries out arithmetic and bitwise operations on integer binary numbers. This is in comparison to a floating-point unit (FPU), which runs and functions on floating-point numbers. An **ALU** is an elementary building block of various types of computing circuits, comprising:

- The central processing unit (CPU) of computers
- FPUs
- Graphics processing units (GPUs)

A single CPU, FPU or GPU may include a variety of ALUs.

### ALU Functions

Some fundamental arithmetic and bitwise logic functions are generally supported by **ALUs**. Fundamental, general-purpose **ALUs** normally comprises these operations in their range of collections:

**Add**: A and B are summed and the sum comes out at Y and carry-out.**Add with carry**: A, B and carry-in are summed and the sum comes out at Y and carry-out.**Subtract**: B is subtracted from A (or vice versa) and the difference comes out at Y and carry-out. For this function, carry-out is efficiently a "borrow" indicator. This operation may also be used to contrast the magnitudes of A and B; in such conditions, the Y output may be unnoticed by the processor, which is only involved in the status bits (specifically zero and negative) that outcome from the operation.**Subtract with borrow**: B is subtracted from A (or vice versa) with borrow (carry-in) and the difference comes out at Y and carry-out (borrow out).

Two's complement (negate): A (or B) is subtracted from zero and the difference comes out at Y.**Increment**: A (or B) is increased by one and the outcome value comes out at Y.**Decrement**: A (or B) is decreased by one and the outcome value comes out at Y.**Pass through**: all bits of A (or B) appear unchanged at Y. This operation is normally used to find out the state of correspondence of the operand or whether it is zero or negative or to put up the operand into a processor register.

### Bitwise logical operations

**AND**: the bitwise AND of A and B comes out at Y.**OR**: the bitwise OR of A and B come out at Y.**Exclusive-OR**: the bitwise XOR of A and B come out at Y.**Ones' complement**: all bits of A (or B) are inverted and come out at Y.

### Bit shift operations

**Arithmetic shift**: the operand is taken care of as a two's complement integer, signifying that the highly noteworthy bit is a "sign" bit and is preserved.**Logical shift**: a logic zero is shifted into the operand. This is used to shift unsigned integers.**Rotate**: the operand is taken care of as a circular buffer of bits so it’s smallest and highly noteworthy bits are successfully adjacent.**Rotate through carry**: the carry bit and operand are cooperatively taken care of as a circular buffer of bits.

Reference: Arithmetic_logic_unit

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