0x 123 is a decimal constant of 16, not a decimal constant of 10. The method to convert 0x 123 into 10 is:1*16+2 *16+3, and the corresponding decimal number is: 256+32+3 = 2965438.

In C-like languages, the binary number 16 is represented by 0X or the beginning of 0x, so:

1~9 16 is expressed in hexadecimal as 0x00 1 ~ 0x09, and 10 ~ 15 is expressed in hexadecimal as 0~0x0f.

In addition, in some programming languages (such as basic), hexadecimal numbers are expressed with the end of h, for example, 123h is 0x 123.