ID Number: Q66431
6.00 6.00a 6.00ax 7.00 | 6.00 6.00a
MS-DOS | OS/2
Summary:
Applications compiled for alternate math using the Microsoft C
Compiler versions 6.0, 6.0a, 6.0ax, and C/C++ version 7.0 are embedded
with function calls in order to perform the floating-point calculations.
This can be observed by viewing the .COD listing file generated when
compiling with the /Fc option.
More information:
The functions you see in the code perform a task similar to the 80x87
instructions that would be needed for the same situation. Therefore,
it is fairly easy to determine what the name of each function means
and what the function does.
Each name is composed of fields similar to the following
__a(far/near call)(segment)(operation)(data type)(reverse/pop)
where
(far/near call) is either "F" or "N". This specifies that the
altmath helper is called either far or near.
(segment) is "f", "s", or "e". If the altmath helper
needs an argument, the compiler will set BX to
point to the argument. If the altmath routine
has an "f" in its segment field, then DS:BX points
to the argument. "s" means that SS:BX points to
the argument and "e" means ES:BX. If no argument
is needed, then "f" is used. (For example, __aNfadd
doesn't need an argument but instead uses st(0)
and st(1) off of the altmath stack, just like the
"fadd" 80x87 instruction.)
(operation) is similar to the 80x87 instructions. "add",
"sub", "mul", "div", "ld" (load to altmath stack),
and "st" (store from stack).
(data type) is one of the following:
"s" for single precision or float.
"d" for double precision or double.
"w" for word or 16 bit integer.
"l" for long or 32 bit integer.
"q" for qword or 64 bit integer.
'' for no data type needed.
This field is used only when bx points to an
argument.
(reverse/pop) is "p", "r" or ''. In most cases, it is not
used. If the operation was a "st" (store), then a
"p" at the end means to pop the stack after the
store. If the operation was div or sub, then an
"r" means to do the reverse version of the
operation.
So, __aNfadds is a near called routine that will add the top of the
altmath stack st(0) with the float (single precision) in DS:BX. This
is similar to "fadd dword ptr ds:[bx]" in 80x87 code.
Additional reference words: 6.00 6.00a 6.00ax 7.00