How to Use SEG Keyword with Arrays in DECLARE and CALLs (51411)

SUMMARY

The examples shown below demonstrate how to use the SEG keyword with arrays. The SEG keyword may be used in either a DECLARE statement or a CALL statement when calling a non-Basic routine, and is used to pass both the segment and offset of a variable (which corresponds to passing a far address).

MORE INFORMATION

When using SEG in the DECLARE statement to pass the far address of an array to a non-Basic routine, the array should be specified as a simple variable without using the array notation, as follows:

   DECLARE SUB TEST(SEG a AS INTEGER)
   DIM a(10) AS INTEGER
   TEST(a(0))

A compilation error will occur if the array is DECLAREd using array notation as follows:

   DECLARE SUB TEST(SEG a() AS INTEGER)
   DIM a(10) AS INTEGER
   TEST(a(0))

Inside the QuickBasic QB.EXE environment, the error message "Expected: , or )" will be displayed for the above DECLARE statement. When compiled from the BC.EXE command line, the following two error messages display:

"Syntax error"
"Formal parameter specification illegal"

When using SEG in an explicit CALL statement there should not be a DECLARE statement. Explicitly using the CALL keyword (instead of using an implied call) takes the place of the DECLARE statement. The correct syntax is as follows:

   DIM a(10) AS INTEGER
   CALL TEST(SEG a(0))

If a DECLARE statement is used with an explicit CALL statement that uses SEG, the error "Parameter type mismatch" displays.