Among the Greek gods Hermes is the swift messenger. The Hermes machine has shown how a computer with a small instruction set can do anything. It has shown how one can represent any computing processes as static bits in a memory.
In these notes we have see how the abstract bit representations of characters, logical values, integer numbers, and pictures, can be used in a `real' computer.
Be assured that the Hermes machine while not being currently commercially available is similar to all of those that are. It is just a simplification of other machines to demonstrate the principles that lay behind the higher level language that you normally use to program. If you have really understood these notes then you now understand Pascal and C in more depth.
The major `resources' available in the Hermes machine is memory and the execution of stored programs. This understanding provides a basis for looking at the cost of any program. A program uses so much memory and runs for so long. Memory can be measured in bits, bytes, words, kilo- or mega-bytes; they are all just multiples of bits. Execution cost is a measure of the length of time the program runs; this can be measured in cpu-cycles, mili- or micro-seconds, seconds, minutes, or hours; again for any given machine, they are all just multiples of one another. This understanding provides a basis for studying the performance of programs which you will probably encounter as a part of CS.231 next year.
The Hermes computer is capable of computing anything any other modern computer is capable of computing. The instructions it uses may not be the most convenient, but they are similar to many machines (or cpu chips) you might buy today. The memory organization used in it is almost universal in modern computers.
The idea of how the Hermes computer works, and how bits are used in it are fundamental computer concepts. These ideas form the basis of all computer processing, and they present a fundamental technology that is exploited in every program. So they are worth understanding.
In these notes we have explored the way the static bits which represent a program can be made more inviting for humans to write, by just changing the representation. This is the idea of assembly language. Higher level languages are extensions of this idea; while every language has its own pro's and con's they all share the computer underneath. This means that if you mentally squint at any language you will see the machine. If some machine limitation is gone (or claims to be gone) in some language the people who have implemented the language have just written a program to create a new, improved, machine (that is probably slower than the original). This is because little comes for free; in computers or in the real world.
The four parts of the Hermes computer are characteristics of all computers on the market today. And the organization of Hermes is similar to that of other computers.
These notes have carried on the notion of the generality of bits;
to show that programs as well as other data can be represented with them.
When it is understood, this turns out to be extremely simple.
It is this power, the power of a stored program computer that gives
computers the potent power they possess. Using that power is entirely
up to the creativity and genus of the people who program them.