## ALP Programming Guide and Reference

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### Default Segment Attribute

For programs running in protected mode, the D bit in executable-segment descriptors specifies the default attribute for both address size and operand size. These default attributes apply to the execution of all instructions in the segment. A clear D bit sets the default address size and operand size to 16 bits; a set D bit, to 32 bits.

Programs that execute in real mode or virtual-8086 mode have 16-bit addresses and operands by default.