How Did We Decide What Computer Values and Instructions Mean?

The earliest computers often had their functions built directly into the hardware, so they weren’t reading general-purpose programs. Programmability came later, when designers created ways to store instructions as data in memory. Early programs could be entered manually or using punched cards, and eventually software was written to load and translate other software. Each layer of abstraction made the process easier for people while ultimately producing the same low-level signals.

The values assigned to machine instructions are mostly arbitrary choices made by the processor designers. For example, a manufacturer might decide that a particular byte means “add two values,” while another byte means “load data into a register.” The CPU’s control circuitry recognizes that pattern and activates the circuits needed to perform the operation. Another processor could use completely different numbers for the same instructions.

A useful analogy is a light bulb controlled by two switches in series. The bulb turns on only when both switches are on, which is an AND operation, but the bulb isn’t interpreting the switches. It simply behaves according to how the circuit was constructed. Computers work similarly: we define an abstract set of operations, then build hardware that carries them out automatically. Standards exist for particular architectures and formats, but there was no universal rule requiring a specific value to mean a specific instruction.

Computers don’t literally understand anything. Their circuits are physically designed to respond to electrical signals in particular ways. A high or low voltage can represent 1 or 0, and transistors can be combined into AND, OR, and NOT gates. Those gates can then be assembled into circuits for arithmetic, memory, comparisons, and other operations.

People such as Boole, Turing, Church, and Babbage helped show that complicated algorithms could be reduced to simple logical and mechanical operations. Once those operations were understood, engineers could implement them with circuits. Studying digital logic, computer architecture, and the idea of a Turing machine is a good way to see how the progression goes from electrical signals to gates, memory, instructions, and eventually programming languages.