Hermes: A Tutorial and Reference Manual - Researcher - IBM
Hermes: A Tutorial and Reference Manual - Researcher - IBM
Hermes: A Tutorial and Reference Manual - Researcher - IBM
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101.2.GettingStarted|ASimple<strong>Hermes</strong>Program<br />
aserver<strong>and</strong>aclient.Clientsarethemostcommontypeofprocess<strong>and</strong> theeasiesttowrite.Inlatersections,we'llseehowtouse<strong>Hermes</strong>towrite connectotherprocesses.Someprogramsmayplaymultipleroles,e.g.both them.Also,theyareusersofservices|notprovidersofservices.Roughly speaking,clientsmakecalls,serversreceivecalls,<strong>and</strong>shellscreate<strong>and</strong> parentprocess|typicallyashellorsystembuilder|dothebindingfor clientcorrespondstoanapplicationsprogramonconventionaloperating increatingprocesses,orbindingoutputports.Theyarecontenttolettheir shells<strong>and</strong>servers. systems.Clientprogramshaveaspecicjobtodo|they'renotinterested<br />
quenceofthefactthata<strong>Hermes</strong>programisanentiredynamicsystem,not simplyyourapplication.Youhavelearnedthefollowing<strong>Hermes</strong>nomenclature:processmodule,process,variable,type,typefamily,typestate,input<br />
program:rstreceiveaparametercallmessagefromtheinitializationport; port,outputport,callmessage,initializationport,initialized,uninitialized, client,server,<strong>and</strong>shell.Youhaveseenthestructureofatypicalclient Summary:Inthissection,youhaveseenthatin<strong>Hermes</strong>,thereisno ports)arevariables,notconstants.Youhaveseenthatthisisaconse-<br />
globaldata,<strong>and</strong>inparticularfunctionnames(which<strong>Hermes</strong>callsoutput<br />
return. 1.3ASecondProgram Beforemovingontothesystemsprogrammingconstructsin<strong>Hermes</strong>,let's thenusetheoutportportspassedinthatcallmessagetoaccessservices.<br />
lookatonemoreclientprogram,whichweshallcallEcho: Youhavelearnedthefollowing<strong>Hermes</strong>statements:receive,call,<strong>and</strong><br />
block receiveParmsfromInit; declare begin Line:Charstring;--linereadfromst<strong>and</strong>ardinput while('true')repeat callParms.GetLine(Line);<br />
type,togetherwithitsassociatedcallmessagetypeiscalledaninterface, programHelloWorld.Therefore,thevariableParmswillhavethesame componentnames<strong>and</strong>typesasinprogramHelloWorld.Aninputport WeassumethattheinitializationportInitisofthesametypeasin returnParms; on(GetLineInterface.EndStream) endblock; endwhile; callParms.PutLine(Line);
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