X=x+ 18 can be written as x+= 18 to simplify the program, and the compiler will treat these two expressions as equivalent when compiling.

X is an integer, accounting for 16 binary bits (two bytes), Y is a long integer, accounting for 32 binary bits (four bytes), and there is also a short integer in the integer, accounting for 8 binary bits (one byte). You assign an integer to a long integer here, and its high bit is filled with the highest bit of the integer.