Format of new executable segment table record:
 00h    WORD    offset in file (shift left by alignment shift to get byte offs)
 02h    WORD    length of image in file (0000h = 64K)
 04h    WORD    attributes
                bit 0: data segment rather than code segment
                bit 1: unused???
                bit 2: real mode
                bit 3: iterated
                bit 4: movable
                bit 5: sharable
                bit 6: preloaded rather than demand-loaded
                bit 7: execute-only (code) or read-only (data)
                bit 8: relocations (directly following code for this segment)
                bit 9: debug info present
                bits 10,11: 80286 DPL bits
                bit 12:     discardable
                bits 13-15: discard priority
 06h    WORD    number of bytes to allocate for segment (0000h = 64K)
Note:   the first segment table entry is entry number 1