Orthogonality in Practice
In many CISC computers, an instruction could access either registers or memory, usually in several different ways. This made the CISC machines easier to program, because rather than being required to remember thousands of individual instruction opcodes, an orthogonal instruction set allowed a programmer to instead remember just thirty to a hundred operation codes ("ADD", "SUBTRACT", "MULTIPLY", "DIVIDE", etc.) and a set of three to ten addressing modes ("FROM REGISTER 0", "FROM REGISTER 1", "FROM MEMORY", etc.). The DEC PDP-11 and Motorola 68000 computer architectures are examples of nearly orthogonal instruction sets, while the ARM11 and VAX are examples of CPUs with fully orthogonal instruction sets.
Read more about this topic: Orthogonal Instruction Set
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“It has always been my practice to cast a long paragraph in a single mould, to try it by my ear, to deposit it in my memory, but to suspend the action of the pen till I had given the last polish to my work.”
—Edward Gibbon (1737–1794)