Critical Mach number Critical Mach number In aerodynamics, the critical Mach number (Mcr or M* ) of an aircraft is the lowest Mach number at which the airflow over some point of the aircraft reaches the speed of sound, but does not exceed it. At the lower critical Mach number, airflow around the entire aircraft is subsonic. At the upper critical Mach number, airflow around the entire aircraft is supersonic. For an aircraft in flight, the speed of the airflow around the aircraft differs considerably in places from the airspeed of the aircraft; this is due to the airflow having to speed up
Mach-O 0 and 255 sections. Mach-O uses the REL relocation format to handle references to symbols. When looking up symbols Mach-O uses a two-level namespace that encodes each symbol into an 'object/symbol name' pair that is then linearly searched for by first the object and then the symbol name. The basic structure—a list of variable-length "load commands" that reference pages of data elsewhere in the file—was also used in the executable file format for Accent. The Accent file format was in turn, based on an idea from Spice Lisp. Under NeXTSTEP, OPENSTEP, macOS, and iOS, multiple Mach-O files can be combined