IDEAL vs. MASM mode

    No formal standard exists for the assembly language. For better or
    worse, the syntax used by Microsoft's assembler (MASM) is followed by
    convention. In addition to supporting MASM syntax, Borland has
    introduced the Ideal mode, a MASM derivative, with a clearer and more
    consistent syntax.

    Ideal mode features include:

       ■ duplicate member names among multiple structures
       ■ complex HIGH and LOW expressions
       ■ predictable EQU processing
       ■ correct handling of grouped data segments
       ■ improved consistency among directives
       ■ sensible bracketed expressions
       ■ 30% faster assembly than MASM mode


    Entering and leaving Ideal mode

    Use the IDEAL and MASM directives to switch between Ideal and MASM modes.
    Turbo Assembler always starts assembling a source file in MASM mode.
    To switch to Ideal mode, include the IDEAL directive in your source
    file before using any Ideal mode capabilities. You can switch back and
    forth between MASM and Ideal modes in a source file as many times as
    you wish and at any place.


    Differences between Ideal and MASM mode

    Ideal mode uses nearly all MASM's keywords, operators, and statement
    constructions. In Ideal mode, however, directive keywords such as
    SEGMENT, PROC, LABEL, and STRUC appear before the identifying symbol
    name.


    Square brackets

    The biggest difference between Ideal and MASM mode expressions is the
    way square brackets function. In Ideal mode, square brackets always
    refer to the contents of the enclosed quantity (i.e. a memory
    reference). Brackets never cause implied additions to occur. Many
    standard MASM constructions, therefore, are not permitted in Ideal
    mode.

    In Ideal mode, square brackets must be used in order to get the
    contents of an item. For example,

       mov    ax,wordptr

    displays a warning message. You're trying to load a pointer (wordptr)
    into the AX register. The correct form is

       mov    ax,[wordptr]

    Using Ideal mode, it's clear you are loading the contents of the
    location addressed by wordptr (in the current data segment at DS) into
    AX.

    If you wish to refer to the offset of a symbol within a segment, you
    must explicitly use the OFFSET operator, as in this example:

       mov    ax,OFFSET wordptr


    Operators

    The changes made to the expression operators in Ideal mode increase
    the power and flexibility of some operators while leaving unchanged
    the overall behavior of expressions. The precedence levels of some
    operators have been changed to facilitate some common operator
    combinations.

    The period (.) structure member operator is far more strict in Ideal
    mode when accurately specifying the structure members you're referring
    to. The expression to the left of a period must be a structure
    pointer. The expression to the right must be a member name in that
    structure.


    Segments and groups

    In Ideal mode, any data item in a segment that is part of a group is
    considered to be principally a member of the group, not of the
    segment. An explicit segment override must be used for Turbo Assembler
    to recognize the data item as a member of the segment.

    MASM (and therefore Turbo Assembler's MASM mode) handles this
    differently; a symbol is treated as part of a segment when the symbol
    is used with the OFFSET operator, but as part of a group when the
    symbol is used as a pointer in a data allocation. This can be
    confusing because when you directly access the data without OFFSET,
    MASM incorrectly generates the reference relative to the segment
    instead of the group.