Beschreibung
nach der Bestellung gedruckt Neuware - Printed after ordering - Source: Wikipedia. Pages: 64. Chapters: Obfuscated code, DLL hell, Spaghetti code, Garbage In, Garbage Out, Not Invented Here, Cargo cult programming, Feature creep, Shotgun debugging, Moral hazard, Vendor lock-in, Magic number, Circle-ellipse problem, Anti-pattern, Dependency hell, Race condition, Tag soup, Software bloat, Copy and paste programming, Magic string, Software rot, Hard coding, Duplicate code, Analysis paralysis, Error hiding, Busy waiting, Boat anchor, Law of the instrument, Call super, Abstraction inversion, Reinventing the wheel, Feature interaction problem, Inner-platform effect, Big ball of mud, Shotgun surgery, Cruft, Constant interface, Action at a distance, Programming by permutation, Extension conflict, Object orgy, Softcoding, Bozo bit, Code smell, Design by committee, God object, Racetrack problem, Stovepipe, Instruction creep, BaseBean, Small matter of programming, Loop-switch sequence, Poltergeist, Continuous obsolescence, Yo-yo problem, Magic pushbutton, Tester driven development, Glossyware, Stovepipe system, Smoke and mirrors, Mushroom management, Input kludge, Accidental complexity, Blind faith, Lava flow, Detail-oriented programming, Coding by exception, Sequential coupling, Creeping elegance, Ambiguous viewpoint, Improbability factor, Interface bloat, Database-as-IPC, Bullet-point engineering, Moloch. Excerpt: In computer programming, the term magic number has multiple meanings. It could refer to one or more of the following: The format indicator type of magic number was initially found in early Seventh Edition source code of the Unix operating system and, although it has lost its original meaning, the term magic number has become part of computer industry lexicon. When Unix was ported to one of the first DEC PDP-11/20s it did not have memory protection and, therefore, early versions of Unix used the relocatable memory reference model. Thus, pre-Sixth Edition Unix versions read an executable file into memory and jumped to the first low memory address of the program, relative address zero. With the development of paged versions of Unix, a header was created to describe the executable image components. Also, a branch instruction was inserted as the first word of the header to skip the header and start the program. In this way a program could be run in the older relocatable memory reference (regular) mode or in paged mode. As more executable formats were developed, new constants were added by incrementing the branch offset. In the Sixth Edition source code of the Unix program loader, the exec() function read the executable (binary) image from the file system. The first 8 bytes of the file was a header containing the sizes of the program (text) and initialized (global) data areas. Also, the first 16-bit word of the header was compared to two constants to determine if the executable image contained relocatable memory references (normal), the newly implemented paged read-only executable image, or the separated instruction and data paged image. There was no mention of the dual role of the header constant, but the high order byte of the constant was, in fact, the operation code for the PDP-11 branch instruction (octal 000407 or hex 0107). Adding seven to the program counter showed that if this constant was executed, it would branch the Unix exec() service over the executable imag.
Bestandsnummer des Verkäufers 9781155317410
Verkäufer kontaktieren
Diesen Artikel melden
