[About The Guide]
Execute a C or Assembler procedure
CALL <idProcedure> [WITH <exp list>]
<idProcedure> is the name of the external procedure to CALL.
WITH <exp list> is an optional list of up to seven expressions of
any data type to pass to the external procedure.
CALL executes a separately compiled or assembled procedure. The
procedure must be defined as FAR and end with a FAR return instruction.
Place parameters on the stack using the C parameter passing convention.
Each parameter consists of a FAR (four-byte) pointer to the actual
parameter value. When necessary you may use the WORD() function to pass
a two-byte binary value in the WITH expression. The DX:BX and ES:BX
registers also contain a copy of the first four bytes of parameter
The procedure must preserve the BP, SS, SI, DI, ES, and DS registers as
well as clear the direction flag.
CALL is a compatibility command and therefore not recommended. It is
superseded by the Extend system which provides functions for passing
data to and from CA-Clipper.
. Character strings: Pass a character argument as a FAR pointer
to a null-terminated string (a string with a 00 hex byte at the end).
. Numeric values: Pass each numeric argument as a FAR pointer
to an eight-byte IEEE floating point value. To pass a parameter as
an integer, use the WORD() function. The WORD() function converts
the numeric value to a two-byte binary integer, and passes the
integer value directly rather than through a pointer. Note that
WORD() will not work for values outside of the #32,767 range since
these values cannot be accurately represented as two-byte integers.
. Date values: Pass each date argument as a FAR pointer to a
four-byte (long) integer containing a Julian day number.
. Logical values: Pass each logical argument as a FAR pointer
to a two-byte binary integer containing zero for false (.F.) and one
for true (.T.) .
. Compiling and linking: CALLed programs must conform to the
- Procedures must be in INTEL 8086 relocatable object file
format with the .OBJ file extension.
- Procedures must follow the C calling and parameter passing
- Procedures must be available to the linker at link time, along
with the library of the source compiler. You will need runtime
support for any language other than assembly language. See your
compiler manual for further information.
. Screen position: When using a CALL statement to access a C or
Assembler routine, the cursor is set to the current screen position
within the C or Assembler routine.
. Microsoft C: Microsoft C versions 5.0 and above place a
leading underscore on function names when they are compiled. To call
them, therefore, you must CALL _<function>.
. dBASE III PLUS: To convert a dBASE III PLUS load module to a
CA-Clipper-compatible module, add the following statements to your
mov ds, dx
Warning! Modifying the parameter values may produce incorrect or
unexpected results and, therefore, is strongly discouraged.
Files Library is CLIPPER.LIB.
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