Many shared library routines require a pointer to a structure rather then a scalar value. ABL provides the DEFINE VARIABLE...AS MEMPTR or VAR MEMPTR... statement to define the variable. Once defined, you can use the MEMPTR variable with a set of ABL statements and functions to build, read, and modify the contents of any C-compatible structure used by your shared library routines. For basic information on the MEMPTR data type and how to use it, see Introduction to External Program Interfaces. This section provides information on using MEMPTR variables as parameters to shared library routines.