Transistor circuits become computing machines when controlled electrical states are composed into logic, storage, and timing.
The path is layered.
flowchart TD mosfet["MOSFET switches"] --> gates["CMOS logic gates"] gates --> combinational["Combinational circuits"] gates --> sequential["Sequential circuits"] combinational --> arithmetic["Arithmetic and selection"] sequential --> state["State and registers"] arithmetic --> processor["Processor behavior"] state --> processor
Combinational Circuits
Combinational circuits produce outputs from current inputs.
Examples include:
- adders
- multiplexers
- decoders
- comparators
An adder is not one magic component. It is a structured network of gates. Those gates are built from transistor circuits.
Sequential Circuits
Computers also need state.
A circuit must sometimes hold a value long enough for later work. Sequential circuits include latches and flip-flops. They use feedback and timing so a bit can persist as a stable electrical state.
Registers are collections of such stored bits arranged for fast access inside a processor.
Clocks
A clock does not create computation by itself.
It coordinates when state is allowed to update. That matters because combinational logic takes time to settle. Sequential circuits sample or transfer values at controlled moments so the machine can move through discrete steps.
Why This Still Has Layers
It is correct that transistors are the physical foundation of digital computers.
It is not useful to explain every software concept directly in terms of transistors.
There are layers:
- MOSFET behavior
- CMOS gates
- combinational and sequential circuits
- machine instructions
- operating systems
- programming languages
- applications
Each layer has its own vocabulary and rules. The value of understanding transistors is not to erase those layers. It is to know what the bottom layer must provide: reliable physical state and controlled transitions.
Final Mental Model
A computer looks like it manipulates symbols, numbers, files, and programs. At the lowest physical layer, it manipulates electrical states.
The durable chain is:
semiconductor structure enables MOSFET control, MOSFET control enables CMOS gates, CMOS gates create reliable voltage states, reliable voltage states become bits, bits become logic and storage, and coordinated logic and storage become computing machines.