| .VARPTR and VARSEG Functions Details. |
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| VARPTR and VARSEG Functions Details |
|
| Syntax |
| VARPTR(variablename) |
| VARSEG(variablename) |
| |
| The variablename may be any BASIC variable, including a record variable |
| or record element. The VARPTR function returns an unsigned integer that |
| is the offset of the variable within its segment. The VARSEG function |
| returns an unsigned integer that is the segment part of the variable's |
| address. If variablename is not defined before VARPTR or VARSEG is called, |
| the variable is created and its address is returned. When variablename is |
| a string variable, VARPTR and VARSEG return the location of the first byte |
| of the string descriptor. |
| |
| Note: Because many BASIC statements change the locations of variables |
| in memory, use the values returned by VARPTR and VARSEG |
| immediately after the functions are used. |
| |
| VARPTR and VARSEG are often used with BLOAD, BSAVE, CALL ABSOLUTE, |
| CALL INTERRUPT, PEEK, POKE, or when passing arrays to procedures |
| written in other languages. |
| |
| When using VARPTR or VARSEG to get the address of an array, |
| use the first element of the array as the argument: |
| |
| DIM A(150) |
| . |
| . |
| . |
| ArrAddress=VARPTR(A(1)) |
| |
| Note: You may no longer use VARPTR to get the address of a file's |
| buffer. Use the function FILEATTR to get information about a |
| file. |
| |
| In addition, programs written in earlier versions of BASIC |
| that used VARPTR to access numeric arrays may no longer work. |
| You must now use a combination of VARPTR and VARSEG. For example, |
| the following QuickBASIC Version 3.0 fragment no longer works |
| correctly: |
| |
| DIM Cube(675) |
| . |
| . |
| . |
| BSAVE "graph.dat",VARPTR(Cube(1)),2700 |
| |
| The fragment would be rewritten as follows: |
| |
| DIM Cube(675) |
| . |
| . |
| . |
| ' Change segment to segment containing Cube. |
| DEF SEG=VARSEG(Cube(1)) |
| BSAVE "graph.dat",VARPTR(Cube(1)),2700 |
| ' Restore BASIC segment. |
| DEF SEG |
| |
| You may use VARPTR alone to get the address of a variable stored in |
| DGROUP. You must use both VARPTR and VARSEG to get the complete |
| address of a variable stored as a far object. |
| |
| The VARSEG function, combined with VARPTR, replaces the PTR86 |
| subprogram used in previous versions of QuickBASIC. |
| |
