Advanced PowerBuilder

Introduction

External functions are functions that are written in languages other than PowerScript and are stored in dynamic link libraries (DLL's). These functions could be written in language such as C/C++, Pascal, etc...

You may want to use external functions, typically in the following situations:

• A call to MS-Windows Application Programming Interface (API) to do low-level DOS and Windows functions and to get system information ( Like Windows system directory, free resources etc. ).
• Whenever there is a need for specialized functions such as Multimedia, Telephony etc..
• When processing speed is an utmost requirement. PowerScript has speed constraints. Functions written in a 3GL like C/C++ are faster.
• Reusing existing code.

A DLL is a file containing executable MS-Windows code. To use an external DLL in PowerBuilder, the DLL must be written using the Pascal calling sequence and the datatypes required to pass to and from the DLL must have an appropriate counterpart in PowerScript. Before you call an external function, make sure to go through the external function's documentation to find out the function syntax, parameters and return values. Even before you start using the external function, you need to declare the external function in PowerBuilder.

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