Which one of units performs calculations steps?

The unit that performs calculation steps in a computer system is the Arithmetic Logic Unit (ALU). The ALU is a component of the Central Processing Unit (CPU) and is responsible for performing mathematical operations (such as addition, subtraction, multiplication, and division) as well as logical operations (such as AND, OR, and NOT) on binary data.

The input unit is responsible for receiving input from external sources, the control unit coordinates and manages the operations of the CPU, and the output unit is responsible for sending output to external devices.