ISPSoft User Manual Then double-click C Global Variables below. The C Global Variables window appears right away. Right-click the blank space of the C Global Variables table and select the Add a Symbol item from the context menu. Then the variable symbol declaration window appears. C variable symbols only support the four data types BOOL , WORD , DWORD and REAL, the start address within the range of D0~D999 and the 1000 consecutive D devices. Then the variable symbol can be used directly in the LD and C programs after the variable declaration is done. 16-4