xerox BCPL Runtime Package Oct77 free download

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(ALTODOCS)BCPLRUNTIME.TTY;3 MON 17-0CT-77 1:42AM PAGE 1 For Xerox Internal Use Only -- October 17, 1977 Bcpl Runtime Package October 16, 1977 1 Bcpl Runtime Package This package is a replacement for the standard Bcpl runtime (the one built into the Alto Operating System), in which nearly all of the operations have been microprogrammed. Typical Bcpl programs run 25 to 30 percent faster than with the standard routines, depending primarily on their frequency of procedure calls and their richness in complex structure references. Use of this package also permits one to Junta to levBasic if desired, for a savings of approximately 500 words of main memory. The microprogrammed runtime is entirely compatible with the standard one. It does not require programs to be modified or recompiled, and it works correctly during calls to the Operating System as well as to your own procedures. The simplest use of this package requires only that you load the necessary microcode into the Ram and call one initialization routine. The package also provides a convenient framework in which to define and microprogram additional emulator opcodes. 1. Standard Use The simplest case applies when you do not need to include any special microcode of your own. The file BcplRuntime.Dm is a dump-format file containing Bcp1Runtime.Br and BcplRuntimeMc.Br. These modules should be loaded with your program, along with the LoadRam procedure, available separately as LoadRam.Br. Early during initialization, your program should execute the following: external [ LoadRam; InitBcplRuntime; RamImage ] if LoadRam(Ramlmage) eq 0 then InitBcp1Runtime() (LoadRam returns zero if it successfully loaded the Ram and a nonzero result otherwise, e.g., because no Ram board is installed.) Once this has been done, the space occupied by LoadRam.Br and BcplRuntimeMc.Br may be reclaimed. Bcp1Runtime.Br must remain resident throughout execution of the program, but it occupies only about 150 words whereas the others consume nearly 3000. InitBcplRuntime sets up a 'user finish procedure' (in the manner described in the O.S. manual, section 3.12), whose purpose is to restore the normal Bcpl runtime routines when the program 'finish'es for any reason. Operation of this mechanism is ordinarily invisible; however, there are two situations in which the programmer must be aware of its workings.