A nanocomputer is a computer that operates at the nanoscale, which is extremely small, typically on the order of one billionth of a meter. It is a computer that is designed to perform tasks on the molecular level and is made up of tiny components such as molecular-scale transistors, nanotubes, and nanowires.

The main principle behind a nanocomputer is the use of quantum computing, which is based on the principles of quantum mechanics. Quantum computing allows for the processing of multiple calculations simultaneously, which makes it faster and more efficient than traditional computing methods.

The components of a nanocomputer are so small that they are subject to quantum mechanical effects such as superposition and entanglement. These effects are used to store and manipulate information in the form of quantum bits, or qubits, which are the basic building blocks of quantum computing.

Nanocomputers are expected to have a wide range of applications, such as in medicine, where they could be used to target and destroy cancer cells or deliver drugs to specific parts of the body. They could also be used in environmental monitoring, where they could be deployed to detect pollutants or monitor water quality in real-time.

However, the development of nanocomputers is still in its early stages, and there are many technical challenges that need to be overcome before they can become a reality. These challenges include improving the reliability and stability of the components and developing new materials and fabrication techniques that are suitable for working at the nanoscale.