FIX: "Operand Expected" Error Message

MS-DOS          | OS/2

The information in this article applies to:

• Microsoft Macro Assembler for MS-DOS, versions 5.0, 5.1, and 5.1a
• Microsoft Macro Assembler for OS/2, versions 5.1 and 5.1a

SYMPTOMS

The expression 'PUSH DWORD PTR OFFSET alabel' causes the Microsoft Macro Assember (MASM) versions 5.0, 5.1, and 5.1a to generate the error message:

   error A2027: Operand expected

RESOLUTION

The line 'PUSH DWORD PTR (OFFSET alabel)' works correctly. Since OFFSET is a unary operator, it should not require parentheses.

STATUS

Microsoft has confirmed this to be a problem in MASM versions 5.0, 5.1, and 5.1a. This problem was corrected in MASM version 6.0.

MORE INFORMATION

It is important to note that the operating system that your program is running on must be capable of supporting 32 bit code segments to be able to run code in 32 bit segments. Most PC based operating systems such as MS-DOS 5.0, Windows 3.0, and OS/2 1.x do not provide support for 32 bit code segments. Newer operating systems and DOS extender packages may provide this support.

Sample Code

; Assemble options needed: none

.MODEL small .386

.STACK 1024

seg32 SEGMENT USE32 a32label DW 4321h seg32 ENDS

.CODE start:

  ;push DWORD PTR (OFFSET a32label) ;This is the MASM 5.0,
                                    ;5.1, and 5.1a workaround
  push DWORD PTR OFFSET a32label
  mov ax, 4C00h
  int 21h