In mathematics, "c" can represent any constant or unknown constant. When we solve some specific problems, we often need to introduce some unknown constants to represent the size of a certain property or quantity, so we can use "C" to represent it. For example, when solving some integral problems in calculus, we use indefinite integral to represent the solution of an integral, which often contains an unknown constant "C".

In computer science, "C" is a widely used programming language, which was created by American computer scientist dennis ritchie in 1972. "C" has the characteristics of high efficiency, simplicity and portability, and can run well in various systems. After "C", there are languages such as "c++" and "c#", all of which are developed on the basis of "C".

In physics, "C" usually stands for the speed of light (English: the speed of light). The speed of light is the limit speed of energy transmission and the fastest speed in the universe. Its value is 299,792,458 meters per second (m/s). In many fields of physics, the concept of light speed is essential, such as electromagnetic wave, relativity and cosmology.