System software

7/21/2019 System software

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Program A

Obj t P f P



Object Program of ProgramA



Program B



Object Program of ProgramB



Program C



ec rogram o rogramC



MACHINE-INDEPENDENT LOADER FEATURES

• Automatically incorporate routines from a

subprogram library into the program being loaded.• Keep track of eternal symbols that are referred

to! but not de"ned! in the primary input to theloader.

• At the end of Pass 1! the symbols in #$%AB thatremain unde"ned represent unresol&ed eternalreferences.

• %he loader searches the library or libraries

speci"ed for routines that contain thede"nitions of these symbols! and processes thesubroutines found by this search eactly as ifthey had been part of the primary input stream.



MACHINE-INDEPENDENT LOADERFEATURES

(Conti

• %he subroutines fetched from a libraryin this 'ay may themsel&es containeternal

• references. (t is therefore necessary torepeat the library search process untilall references are resol&ed.

•

(f unresol&ed eternal references remainafter the library search is completed!these must be treated as errors.



Load!" O#tions

• T$#ica% %oad!" o#tion 1&

A%%o's t! s!%!ction o) a%t!"nati*!so+"c!s o)

in#+t,

• E & INCLUDE #"o."a/-na/!(%ib"a"$-na/! /i.t di"!ct t!%oad!" to "!ad t! – designated object program from a

library and treat it as if it 'ere part of

the primary loader input.



Load!" O#tions(Conti

• Load!" o#tion 0& A%%o's t! +s!" tod!%!t! !t!"na% s$/bo%s o" !nti"! cont"o%

• sections.

•

E & DELETE cs!ct-na/! might instruct theloader to delete the named control section)s*from the set of programs being loaded.

• CHANGE name1! name+ might cause the

eternal symbol name1 to be changed toname+ 'here&er it appears in the objectprograms.



Load!" O#tions(Conti

• Load!" o#tion & In*o%*!s t!a+to/atic inc%+sion o) %ib"a"$"o+tin!s to satis)$ eternal references.

•

E, & LIBRAR2 M2LIB – $uch user,speci"ed libraries are normally

searched before the standard systemlibraries. %his allo's the user to use special&ersions of the standard routines.

• NOCALL STDDE34 PLOT4 CORREL – %o instruct the loader that these eternal

references are to remain unresol&ed.

System software

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