Chain loadingFrom Wikipedia, the free encyclopediaChain loading
is a method used by computer programs to replace the currently
executing program with a new program, using a common data area (a
so-called core common area) to pass information from the current
program to the new program. It occurs in seeral areas of
computing.!hain loading is similar to the use of oerlays. "ike the
use of oerlays, the use of chain loading increases the I#$ load of
an application. %nlike oerlays, howeer, chain loading replaces the
currently executing program in its entirety. $erlays usually
replace only a portion of the running program.Contents & !hain
loading in boot manager programs ' !hain loading in %nix ( !hain
loading in )*+I! programs , -eferencesChain loading in boot manager
programs In operating system boot manager programs, chain loading
is used to pass control from the boot manager to a boot sector. .he
target boot sector is loaded in from disk, replacing the in-memory
boot sector from which the boot manager itself was bootstrapped,
and executed.Chain loading in Unix In %nix (and in %nix-like
operating systems), the exec() system call is used to perform chain
loading. .he program image of the current process is replaced with
an entirely new image, and the current thread begins execution of
that image. .he common data area comprises data such as the
process/ enironment ariables, which are presered across the system
call.Chain loading in BASIC programs In )*+I! programs, chain
loading is the puriew of the CHAIN statement (or, in !ommodore
)*+I!, the LOADstatement), which causes the current program to be
terminated and the chained-to program to be loaded and inoked
(with, on those dialects of )*+I! that support it, an optional
parameter specifying the line number from which execution is to
commence, rather than the default of the first line of the new
program). .he common data area aries according to the particular
dialect of )*+I! that is in use. $n ))! )*+I!, for example, only a
specific subset of all ariables are presered across a !0*I1. $n
other )*+I!s, the COMMON statement can be used in con2unction with
CHAIN to specify which ariables are to be presered as common data
across a chain operation.!hain loading permits )*+I! programs to
execute more program code than could fit into aailable program and
ariable memory. *pplications written in )*+I! could thus be far
larger than the si3e of working memory, ia a set of cooperating
programs that CHAIN back and forth amongst themseles as program
flow moes within the oerall application.References 4chain loading4
(http5##www.gnu.org#software#grub#manual#html6node#!hain677'dloading.html).
GNU GRUB manual.89gina & de ' !hain loading - Wikipedia, the
free encyclopedia7:#7;#'7&(
http5##en.wikipedia.org#wiki#!hain6loading Orlando Lee Stevenson
(December 1985). "Commodore Program Chaining"
(htt!""###.atarimaga$ines.com"com%te"iss%e&'"()1*1*Commodore*Program*Chaining.h).
COMPUTE! (&')! 11). Chapter 7: Multiprogramming
(htt!""###.+a,s.org"docs"art%"ch-'s-..html). "Sec%rit/ 0raers and
1ernstein Chaining". Taxonomy of Unix PC Metho!". in The #rt of
Unix Programming.2etrieved +rom
"htt!""en.#i3iedia.org"#"inde4.h5title6Chain*loading7oldid65-)-81.&&"
Categories!Oerating s/stem technolog/ Process (com%ting) 8his age
#as last modi+ied on .5 9%l/ .-1. at -8!1&. 8e4t is available
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trademar3 o+ the 0i3imedia @o%ndation= Anc.= a non;ro+it
organi$ation.PBgina . de . Chain loading ; 0i3iedia= the +ree
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htt!""en.#i3iedia.org"#i3i"Chain*loading
