Processor :Controls the operation of the computer and performs the data processing function
referred to as CPU (Central Processing Unit) when there is only one processor
Memory: Stores data and programs, typically volatile
referred to as real or primary memory
I/O modules (or I/O controllers): Hardware that moves data between computer and external environment (i.e. disks, keyboard, display, network)
System bus: Communication among processors, memory, and I/O modules