%d is used to output the actual length of decimal integer data; %c is output in character form, only one character is output; %f is used to output single or double precision degrees in decimal form, implicit Output 6 decimal places.

C language contains a wide range of data types, including not only traditional character types, integers, floating point types, array types and other data types, but also data types that other programming languages ??do not have, among which Pointer type data is the most flexible to use, and various data structures can be calculated through programming.

Extended information:

If a variable name is followed by a number in square brackets, the declaration is an array declaration. Strings are also a type of array. They end with an ASCII NULL array. It is important to note that the index value within the square brackets starts from 0.

C language strings are actually char arrays ending with '\0' characters. Using character types does not require a library reference, but using strings requires some functions in the C standard library for parsing. Functions that operate on strings. They are different from character arrays. Using these functions requires referencing the header file .

In C language, input and output are implemented through a set of functions in the standard library. In ANSI C, these functions are defined in the header file ;