This is all you need to know about the Hermes machine. If you really understand it then you can easily program it. You should also be able to see that one can represent programs as bits. The technique for representing anything is to define an exact meaning for the bits and the use that representation to manipulate the symbols within the machine. For pictures bits represent the color and intensity of each element of the picture, For programs the bits represent atomic actions that will be performed by the machine to accomplish the goals of the program. The Hermes computer has only 22 instructions, but it can compute anything that any other program can compute.
Pascal tries to make the machine less flexible and more understandable
by limiting what can be done to a set of bits. It does this by giving
types to the bits, creating enumerated types, chars, integers, and so on.
This often helps to clarify your thinking, and makes you keep a
consistent view of data throughout your program,
but it also hides from you the great abstraction of bits
as a general information carrier.
It is this abstraction that makes a computer the great symbol processor
that it is, and it is the fundmental concept that makes the glory and
magic behind computers.
This concept should stay in your understanding,
and come to your aid when you need it.