printf格式说明符遵循以下原则：
%[flags][width][.precision][length]specifier
%[标志][宽度][.精度][长度]说明符
| specifier | Output | Example |
|---|---|---|
| d or i | 带符号的十进制整数 | 392 |
| u | 无符号的十进制整数 | 7235 |
| o | 无符号八进制数字 | 610 |
| x | 无符号十六进制整数 | 7fa |
| X | 无符号十六进制整型（大写） | 7FA |
| f | 十进制浮点数，小写 | 392.65 |
| F | 十进制浮点数，大写 | 392.65 |
| e | Scientific notation (mantissa/exponent), lowercase | 3.9265e+2 |
| E | Scientific notation (mantissa/exponent), uppercase | 3.9265E+2 |
| g | Use the shortest representation: %e or %f | 392.65 |
| G | Use the shortest representation: %E or %F | 392.65 |
| a | Hexadecimal floating point, lowercase | -0xc.90fep-2 |
| A | Hexadecimal floating point, uppercase | -0XC.90FEP-2 |
| c | 字符 | a |
| s | 字符串 | sample |
| p | 指针地址 | b8000000 |
| n | Nothing printed. The corresponding argument must be a pointer to a signed int. The number of characters written so far is stored in the pointed location. |
|
| % | A % followed by another % character will write a single % to the stream. | % |