Back in the early days of computers, the programming was done by “hard-wiring”the computer to perform a certain sequence of instructions.  People spent hours determining the wiring scheme followed by more hours actually getting the wiring right…

Fortunately, a fellow named Dr. John Von Neumann came up with a better idea. He developed the concept of actually storing the program in the computer’s memory rather than spending all the time hard-wiring the damn thing.  Hence, the basis for today’s computer technology was born. As you should suspect by now, most computers (including your smartphones and tablets) are “Von Neumann” machines.  They run “stored programs” containing “machine language instructions” under control of something inside your device called a “program counter” that figures out what instruction to do next.

How does this work?  Well, the computer’s central processing unit (CPU) typically has an internal “clock” that “ticks” at some speed such as 2 Gigahertz per second.  During each clock tick or “cycle,” specific things happen inside the computer.  For example, during one clock cycle, an instruction may be fetched from memory and decoded.  During the next clock cycle, the instruction starts execution; during the next clock cycle, a piece of data may be retrieved from memory and added to another piece of data, and so on and so on.

Of course today’s computers are much more sophisticated than those of Von Neumann’s era… and a lot smaller and faster.  The machines Von Neumann worked with filled floors in buildings and took almost forever to do what your hand-held smartphones and tablets do in microseconds.  But, as sophisticated as today’s devices are, they still do what Dr. Von Neumann told them to do years ago.