Memory allocation
In C, memory is allocated by the application for input and output buffers. The application passes the address and length of the buffer to a driver.
In some Tcl instances, a buffer must be specified. The argument type is listed in the ODBC documentation as PTR. The application passes the name of a Tcl variable and the length. Memory management is handled by Tcl.
In some C instances, the parameter is coded as an array of input or output values. The Tcl counterpart is an array indexed with integers starting at "0."