Important Notice

The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.

 ◄Example►                                   ◄Up► ◄Contents► ◄Index► ◄Back►
────────────────────────────────────────────────────────────────────────────
 
  Syntax:   qualifiedtype PTR expression
            PTR qualifiedtype
 
  See also: TYPE, THIS, qualified type
 
  Description:
 
     The first syntax treats <expression> as having the specified type.
     Type casting can be used with forward references or unlabeled
     addresses to specify a reference size, type, or distance.
 
     The second syntax is used in defining qualified types.
     See: ◄qualified type►
 
     The PTR keyword can also appear in qualified types to indicate
     that the type is a pointer variable.
 
     The <qualifiedtype> can be any qualified type. The <expression>
     can be any valid expression. If <qualifiedtype> is a distance,
     <expression> cannot be a memory expresssion or a data label.
     See: ◄qualified type►
 
     You can use a constant as the left operand to PTR in compatibility mode.
     Otherwise, you must use a type expression. With OPTION M510, a constant
     must have a value of 1 (BYTE), 2 (WORD), 4 (DWORD), 6 (FWORD),
     8 (QWORD) or 10 (TBYTE). The assembler treats the constant as the
     parenthesized type. Note that the TYPE operator yields a type expression,
     but the SIZE operator yields a constant.
 
     ; With OPTION M510
 
          MyData  DW      0
 
             mov     WORD PTR [bx], 10           ; Legal
             mov     (TYPE MyData) PTR [bx], 10  ; Legal
             mov     (SIZE MyData) PTR [bx], 10  ; Legal
             mov     2 ptr [bx], 10              ; Legal
 
     ; Without OPTION M510
 
          MyData  WORD    0
 
             mov     WORD PTR [bx], 10           ; Legal
             mov     (TYPE MyData) PTR [bx], 10  ; Legal
     ;       mov     (SIZE MyData) PTR [bx], 10  ; Illegal
     ;       mov     2 PTR [bx], 10              ; Illegal
 
 
 
  Example:
 
     mov        ax, (MyStruct PTR [bx]).Username
     fld        TBYTE PTR MaxConvolution
     INVOKE     MyRoutine, PTR TempValue
 
     Under MASM 5.1, applying the PTR operator to a data initializer de-
     termines the size of the data displayed by CodeView. You can still use
     PTR in this manner in MASM 6.1, but it does not affect CodeView typing.
     Defining pointers with the TYPEDEF directive allows CodeView to generate
     correct information.
                                    -♦-