jBase Infobaisc Function CALLC

The CALLC command transfers program control to an external function (c.sub.name). The second form of the syntax calls a function whose name is stored in a jBASE BASIC variable (@var). The program could pass back return values in variables. CALLC arguments can be simple variables or complex expressions, but not arrays. Use CALLC as a command or function.

Command Syntax

CALLC c.sub.name [(argument1[,argument2]...)]
CALLC @var [(argument1[,argument2]...)]

Calling a C Program in jBASE

You must link the C program to jBASE before calling it from a BASIC program. Perform the following procedure to prepare jBASE for CALLC:

• Write and compile the C program.
• Define the C program call interface
• Build the runtime version of jBASE (containing the linked C program).
• Write, compile, and execute the Basic program

Calling a Function in Windows NT

The CALLC implementation in jBASE for Windows NT or Windows 2000 uses the Microsoft Windows Dynamic Link Library (DLL) facility. This facility allows separate pieces of code to call one another without permanently binding together. Linking between the separate pieces occurs at runtime (rather than compile time) through a DLL interface. For CALLC, developers create a DLL and then call that DLL from jBASE

Example

In the following example, the called subroutine draws a circle with its center at the twelfth row and twelfth column and a radius of 3:

RADIUS = 3
CENTER = "12,12"
CALLC DRAW.CIRCLE(RADIUS,CENTER)

In the next example, the subroutine name is stored in the variable SUB.NAME, and is indirectly called:

SUB.NAME = DRAW.CIRCLE
CALLC @SUB.NAME(RADIUS,CENTER)

The next example uses, CALLC as a function, assigning the return value of the subroutine PROGRAM.STATUS in the variable RESULT:

RESULT = CALLC PROGRAM.STATUS