The so-called character type, plastic type and floating-point type are just one format of data and can be converted to each other. That is, a character constant can be converted into an integer constant, and vice versa, if the integer constant corresponds to a character in ascii code. Like 67, if you don't add'', then it can also be converted into text, but the writing is different. The same is true for' a', which can also be written as int to calculate the need.