R[%reg] denotes the contents of register %reg.

Mb[addr] denotes the contents of b memory locations
beginning at address addr.

Operands are stored in one of several different operand forms.

 - the instruction itself (immediate)
 - a register
 - memory

                            Some Operand Forms
Type        Name        Form        Example            Value
----        ----        ----        -------            -----
Immediate   immediate   $nnn        $0xc               12
Register    register    %reg        %esp               R[%esp]
Memory      absolute    nnn         0xc                M[12]
Memory      indirect    (%reg)      (%ebp)             M[ R[%ebp] ]
...