In the original von Neumann architecture, he explains an Arithmetic and Logic Unit and a Control Unit. In modern computers, the second unit is located in a single integrated circuit (IC - Integrated Circuit), which is usually called a CPU (Central Processing Unit).
Arithmetic and Logic Unit, or Arithmetic Logic Unit (ALU), are tools that perform basic implementation as the implementation of arithmetic (addition, subtraction, and the like), the implementation of logical (AND, OR, NOT), and the implementation of the comparisons (for example, comparing the contents of two slot for equality). In these units that do "work" is real.
Save the command control unit is now done by computer, ordered the ALU to implement and got back the information (from memory) needed to execute the order, and move back the results to the appropriate memory location. Once that happens, the control unit to go to the next command (usually located in the next slot, except if the order is a jump command that tells the computer that orders placed at other locations).
Source : http://id.wikipedia.org/wiki/Komputer#Pemrosesan