The value range of 16-bit integer is between -999 and +999, which is for BCD codes. BCD codes are represented by binary codes of ten values "0" to "9". Also called 842 1 code. When BCD code is stored in a word with 16 bits, 0-3 bits represent one bit, 4-7 bits represent ten bits, 8-1/bits represent hundreds, and 12- 15 bits represent symbols. The sign bit is located in the higher decimal number, only involving 15 bits. The state of "0" indicates a positive number, and the state of "1" indicates a negative number. Therefore, the value range of 16 bit BCD code is 999. The same is true for 32-bit BCD codes, so the range of 32-bit BCD codes is 999999.

In S7-300, numbers are generally represented by INT( 16 signed integer), DINT(32 signed long integer) and REAL(32 floating point number). If you want to have a deeper understanding of the data types of S7-300, you should program more at ordinary times, and practice makes perfect.