Figure 16.12 is a simple example of these concepts. Assume a processor with
a single accumulator and several internal registers, such as a program counter and
a temporary register for ALU input. Figure 16.12a shows a highly vertical format.
The first 3 bits indicate the type of operation, the next 3 encode the operation,
and the final 2 select an internal register. Figure 16.12b is a more horizontal approach,
although encoding is still used. In this case, different functions appear in
different fields.