%d outputs an integer format, which is a decimal number. %c outputs a character format, which is a single letter or symbol. %f outputs a floating point number, which is a number with four decimal places. , for example, 10.0000%ld outputs long integer format, almost the same as decimal, except that it can output very large numbers %u outputs unsigned numbers, this basic output is similar to %d %s outputs strings, generally output All characters %lf of a char array output long floating-point numbers, which are so-called double-precision floating-point numbers. The double type can output very large numbers with decimal places. These are the most commonly used ones. People behind you can add them~