Project Overview:

The Arithmetic Logic Unit (ALU) is one of the most essential components of a CPU (Central Processing Unit). It is responsible for performing all the arithmetic and logical operations required by a program. Without the ALU, a computer cannot process numerical data or perform logical comparisons, making it a critical part of any computing system.

Arithmetic Operations:

The ALU performs basic arithmetic operations such as:

Addition: Adding two numbers (e.g., 5 + 3 = 8).

Subtraction: Subtracting one number from another (e.g., 5 - 3 = 2).

In some advanced systems, it may also handle multiplication and division, though in simpler systems like an 8-bit computer, these might be implemented as repeated addition or subtraction.

Logic Operations:

The ALU can compare values and perform logical operations such as:

AND: Compares two binary inputs and outputs 1 only if both are 1.

OR: Outputs 1 if at least one input is 1.

NOT: Inverts a binary value (1 becomes 0, and 0 becomes 1).

XOR: Outputs 1 if the inputs are different.

These operations are useful for decision-making processes in a program.

Interaction with Registers:

The ALU receives its input data (operands) from registers, such as Register A and Register B, which temporarily store the values to be processed. After performing the specified operation, the ALU sends the result back to one of the registers (typically Register A). This result can then be used for further operations or sent to the output.

Control Signals:

The ALU operates under the direction of the Control Unit (CU). The Control Unit decodes the instruction held in the Instruction Register (IR) and tells the ALU what operation to perform (e.g., ADD, SUB, AND). The ALU does not decide what to do on its own; it simply executes the commands given to it.

Flags and Status Updates:

The ALU generates flags based on the results of its operations. These flags provide important feedback to the Control Unit and other parts of the CPU. Common flags include:

1. Zero Flag: Set to 1 if the result of the operation is 0.
2. Carry Flag: Indicates if there was a carry out of the most significant bit during addition.
3. Negative Flag: Indicates if the result is negative (in signed operations).
4. Overflow Flag: Set if the result of an operation exceeds the range of the ALU.

Data Flow in the ALU:

The ALU gets its input from the data bus via registers (e.g., Register A and Register B).

The operation to be performed is defined by the opcode, decoded by the Control Unit.

After processing, the result is sent back to a register (e.g., Register A) or forwarded to the output via the Output Register.