Programming Guide : Using 3GL in Your Application : How You Can Use Exec 4GL Statements in 3GL Procedures : How You Can Pass Structured Data
 
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How You Can Pass Structured Data
Structured data is passed to 3GL as a handle. You reference the handle in the exec 4GL statements whenever you want to reference the object or array. The handle is passed as a 4-byte integer. To store a handle passed in from 4GL, use a 32-bit integer data type.
After control is returned to 4GL, a later call from 4GL to 3GL cannot use the handle stored earlier in a static variable because the earlier handle is no longer valid. Therefore, the 3GL routine should not store a handle in a static variable.