The Carnot Cycle consists of four steps:

1. Isothermal Expansion
2. Adiabatic or Isentropic Expansion
3. Isothermal Compression
4. Adiabatic or Isentropic Compression

The cycle is ordinarily plotted on two axes in two different ways: Pressure and Volume, in which case the cycle is a curvy quadrilateral and descending to the right, or Temperature and Entropy, in which case the cycle is a nice rectangle that emphasizes the isothermal and adiabatic (isentropic) aspects of the steps.

References:

https://en.wikipedia.org/wiki/Carnot_cycle

Images of the Carnot Cycle from Google search.

Tip of the hat to:

Stuart Kauffman / Investigations

Also please see the previous posts:

https://equivalentexchange.wordpress.com/2012/01/27/thermodynamics-and-the-four-thermodynamic-potentials/

https://equivalentexchange.wordpress.com/2013/05/24/the-four-laws-of-thermodynamics/

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