Arithmetic Micro-operations in Computer Architecture: The Building Blocks of CPU Arithmetic
Explore arithmetic micro-operations—the fundamental instructions executed by a CPU's ALU. This guide details basic operations (addition, subtraction, increment, decrement), more complex operations (multiplication, division), and how they combine to perform complex arithmetic calculations.
Arithmetic Micro-operations in Computer Architecture
What are Arithmetic Micro-operations?
Arithmetic micro-operations are low-level instructions performed by a CPU's (Central Processing Unit's) ALU (Arithmetic Logic Unit) on numeric data stored in registers. These are the fundamental building blocks for more complex arithmetic computations.
Basic Arithmetic Micro-operations
The basic arithmetic micro-operations include:
- Addition (+)
- Subtraction (-)
- Increment (+1)
- Decrement (-1)
- Shifting (left or right)
Additional Arithmetic Micro-operations
Beyond the basic operations, more complex operations are often implemented as micro-operations:
- Add with carry
- Subtract with borrow
- Transfer (or Load)
Symbolic Representation of Arithmetic Micro-operations
| Symbolic Representation | Description |
|---|---|
| R₃ ← R₁ + R₂ | Add the contents of registers R₁ and R₂; store the result in R₃. |
| R₃ ← R₁ - R₂ | Subtract the contents of R₂ from R₁; store the result in R₃. |
| R₂ ← R₂' | Take the one's complement of R₂. |
| R₂ ← R₂' + 1 | Take the two's complement of R₂ (negate). |
| R₃ ← R₁ + R₂' + 1 | Add the two's complement of R₂ to R₁ (subtraction). |
| R₁ ← R₁ + 1 | Increment R₁ by one. |
| R₁ ← R₁ - 1 | Decrement R₁ by one. |
Conclusion
Arithmetic micro-operations are the fundamental building blocks of a CPU's ability to perform arithmetic calculations. These low-level operations are combined to implement more complex arithmetic functions. Note that operations like multiplication and division are often implemented using sequences of these more basic micro-operations.