October 16, 1985

                Microsoft Macro Assembler Package
                          Version 4.00

==( MASM.EXE )==================================================

New Feature 

    The following error message has been added to MASM: 

      102   Segment near (or at) 64K limit. 

    This is a warning, not a severe error, so the object module 
    is not deleted.  It occurs when a code segment has grown to 
    a large size (within 36 bytes of 64K) and is detected when 
    the segment is closed with the ENDS directive.  It does not 
    occur with data segments.  A code segment is a segment which 
    contains at least one instruction.  


    The statements "DW ?" and "DW 1 DUP(?)" are not identical; 
    they cause MASM to generate different object files.  The 
    first form is "indeterminate," meaning MASM places the 
    default value 0 in the object module.  The second form is 
    "undefined," meaning MASM does not generate a value for the 
    declaration in the object module.  The only indication that 
    an undefined value has been processed is that records placed 
    in the object module following the declaration have their 
    offsets adjusted forward.  In most cases, the distinction is 
    trivial, but in segments with the COMMON combine type, the 
    distinction is very important.  

    Note that if two modules contain definitions for a variable, 
    one with "?" and one with an explicit value, the variable in 
    the executable file will have either 0 or the value, 
    depending on the order of linking.  If the modules had 
    "n dup (?)" and "n dup (m)" where n and m are numbers, the 
    value would be "n dup (m)" regardless of the link order.  
    When COMMON segments are involved, "1 dup (?)" should always 
    be used instead of "?". 


    The occurrence of square brackets ([]) in the address field 
    of instructions indicates a memory reference only when at 
    least one of the registers BX, BP, SI, or DI is contained in 
    the brackets.  For all other purposes, the square brackets 
    indicate addition.  For example, "mov ax,[bx]" moves the 
    word to which BX points into AX, but "mov ax,[2]" moves the 
    immediate value 2 into AX.  To generate a memory reference 
    to an absolute offset, use "mov ax,ds:[2]".  Since DS is the 
    default segment register for memory references, the segment 
    override will not be put in the object file, but it does 
    tell MASM that "[2]" is a memory reference, not an immediate 


    If neither the /R nor the /E option is used during assembly, 
    MASM defaults to the Microsoft real number format.  See 
    Chapter 2 of the Reference Manual for information on the 
    syntax for declaring real numbers.  


    The definition of names on page 15 and 16 of the Reference 
    Manual is incomplete.  A name is a sequence of characters 
    consisting of letters, digits, and the following special 
    characters: underscore (_), percent sign (%), question mark 
    (?), dollar sign ($), at sign (@), or period (.).  These 
    limitations apply: 

         o  A name cannot begin with digit, though a digit can 
            be imbedded (sym1 but not 1sym).  

         o  A name may begin with a period, but cannot have an 
            imbedded period (.sym1 but not sym.1). 

         o  A name cannot correspond to a reserved word or 
            symbol (for example, AX, ?, $, mov, and PAGE are 


    The description for assembler error 49, "Illegal use of 
    register," should read: 

      Use of a register with an instruction where no valid 
      register is possible.  

==( SYMDEB.EXE )================================================


    The WO and BY operators in expressions assume DS as the 
    segment; the BP and SP registers in expressions assume SS as 
    the segment.  


    The MS-DOS terminate function (4Ch) will terminate SYMDEB 
    and return to MS-DOS if you use the Assemble command (A) to 
    assemble the function call, and then try to execute it from 
    inside SYMDEB.  This is because SYMDEB executes the function 
    directly instead of executing the program containing the 

    For example, if you assemble the sample program BELL.COM 
    shown on page 102 of the User's Guide, and then execute it 
    from inside the debugger, SYMDEB will terminate.  However, 
    if you save the program (as shown on page 162 of the User's 
    Guide), then restart with BELL.COM as the executable file, 
    SYMDEB will execute the program without terminating.  


    Microsoft reserves certain software interrupts for special
    uses.  SYMDEB understands some of these special uses, and
    interprets surrounding bytes as data for the interrupts.
    If you use a reserved interrupt value, you should be aware
    that SYMDEB may disassemble nearby code based on its
    special understanding of the use of that interrupt.


    When using the Breakpoint Set command (BP), the optional 
    quoted command string cannot exceed 29 characters.  

==( MAPSYM.EXE )================================================


    Mapsym has a limitation of 10,000 source lines per source 
    file.  If your source file has more than 10,000 source 
    lines, MAPSYM will truncate the number of lines that go into 
    the symbol (.SYM) file to 10,000.  If you require the source 
    line information, break the source file into two or more 

==( MAKE.EXE )==================================================


    In the description of MAKE inference rules on page 210 of 
    the User's Guide, the order of the target and dependent 
    extensions is reversed in both the syntax description and 
    the example.  

    The syntax description should read:


    The sample description file at the bottom of the page should 

            MASM $*.asm,,;

      test1.obj: test1.asm

      test2.obj: test2.asm
            MASM test2.asm;

    Note that the syntax for inference rules (dependent 
    extension given first) is different than the syntax for 
    target/dependent descriptions (target file given first).  

==( General Information )=======================================

    When reporting problems with any program in the Macro 
    Assembler package, please provide the following information 
    to help us in tracking down the problem:

      o  The program version number from the logo that is 
         printed out when you invoke the program 

      o  The version of DOS you are running (use the DOS VER 

      o  Your system configuration (your machine, total memory, 
         total free memory at execution time, etc.) 

      o  The command line, responses to prompts, or response 
         file used to invoke the program 

      o  Appropriate source, include, listing, library, or map 
         files for the program you were working on when the 
         problem occurred

    Please use the Software Problem Report at the back of the 
    manual to send the information to Microsoft.