Digital

NAME

PRESENTATION GROUP SPECIFICATION − Specifies a set of interfaces to presentation procedures
 

SYNOPSIS

 PRESENTATION GROUP SPECIFICATION <presentation-group-name>
 
     SOURCE LANGUAGE IS { C | COBOL } ;
 
     [ INITIALIZATION PROCEDURE IS <presentation-procedure-name>; ]
     [ TERMINATION PROCEDURE    IS <presentation-procedure-name>; ]
 
     { PROCEDURE <presentation-procedure-name>
         SENDING   { <argument> [ ,... ]  } ;     } [ ... ]
 
     { PROCEDURE <presentation-procedure-name>
         RECEIVING { <argument> [ ,... ]  } ;     } [ ... ]
 
     { PROCEDURE <presentation-procedure-name>
         SENDING   { <argument-1> [ ,... ]  }
         RECEIVING { <argument-2> [ ,... ]  } ;   } [ ... ]
 
 END PRESENTATION GROUP SPECIFICATION ;

PARAMETERS

       •presentation-group-name
 
An unqualified external identifier giving the name of the presentation group, used in the CALL PRESENTATION statement to identify the presentation group in which the presentation procedure is found.
 
The presentation group name has a maximum limit of 17 characters; characters beyond 17 are truncated.

       •computer-language
 
An operating system name giving the source language in which the presentation procedures are written. All presentation procedures in the same presentation group specification must be written in the same language. The supported languages are:
 
  COBOL
  C
 
The source language must match the programming language used to code the set of presentation procedures within the presentation group. See ACMSxp for DIGITAL UNIX Installation Guide, ACMSxp for OpenVMS Alpha Installation Guide, and ACMSxp for Windows NT Installation Guide to determine the language products and versions supported for each platform. 

       •presentation-procedure-name
 
A qualified external identifier naming an initialization presentation procedure, a presentation procedure, or a termination presentation procedure within the presentation group being defined. A name for a presentation procedure defines an entry point in the presentation group for a user-written procedure and must be unique within the input source file. A presentation procedure name must match the entry point for the presentation procedure.

       •argument
 
An unqualified external identifier specifying the data to be sent to the presentation procedure or to be received from the presentation procedure.
 
Each argument specified refers to a data type definition. The fields within the data type definition must match in order, type, and size either with the workspace fields within the corresponding workspace name in the SENDING phrase of the send or transceive exchange, or the RECEIVING phrase of the receive or transceive exchange.
 

DESCRIPTION

 
ACMSxp Desktop software supports a variety of commercial presentation tools, for example, Visual Basic and Visual C++. If you use ACMSxp Desktop software, you do not need to write a presentation group specification or presentation procedures as described here. However, if you do write presentation group specifications, the compiler validates whether the workspaces passed in presentation procedure calls are correct.
 
If you do not use ACMSxp Desktop software, all the presentation procedures in the same presentation group must be written in the same language, as specified in the SOURCE LANGUAGE IS option.
 
The presentation group specification:

oMaps the names of workspaces sent to the presentation procedure, received from the presentation procedure, or both, to a user-written presentation procedure

oSpecifies arguments to be accepted from the task

oSpecifies arguments to be returned to the task

oSpecifies an initialization procedure to establish any initial context

oSpecifies a termination procedure to release context no longer required

 
A presentation group specification must contain at least one send, receive, or transceive exchange.
 
The INITIALIZATION PROCEDURE IS option identifies the presentation initialization procedure. A presentation initialization procedure establishes context required by a presentation procedure, and has the arguments described in the Initialization Procedure section of the PRESENTATION PROCEDURE topic.
 
The TERMINATION PROCEDURE IS option identifies the presentation termination procedure. The presentation termination procedure invalidates the presentation group context established by the initialization procedure. The presentation termination procedure is invoked when the presentation group context is no longer required.
 
The semantics of the SENDING and RECEIVING options are:

oThe SENDING arguments are passed from the task to the presentation procedure. 

oThe RECEIVING arguments are passed from the presentation procedure to the task. 

If SENDING and RECEIVING arguments are specified in the same CALL PRESENTATION statement, the arguments are sent and received in the same operation. 

If a presentation procedure modifies an argument passed using SENDING, the results are no longer valid. 

oThe arguments in the presentation group SENDING phrase for the presentation procedure must match in order and number with the arguments specified on the corresponding CALL PRESENTATION SENDING phrase in the task definition. 

oThe arguments in the presentation group RECEIVING phrase for the presentation procedure must match in number and order with the arguments specified on the corresponding CALL PRESENTATION RECEIVING phrase in the task definition. 

oThe presentation procedure specified by the presentation-procedure-name parameter in the CALL PRESENTATION statement is called when the task executes a CALL PRESENTATION statement. 

oThe following list of arguments is passed to the presentation procedure specified by the presentation-procedure-name parameter in the CALL PRESENTATION statement:

-Presentation group handle-read-only, integer

-Workspaces in the order defined in SENDING, each read-only

-Workspaces in the order defined in RECEIVING, each write-only

-If both SENDING and RECEIVING are specified, the workspaces in SENDING are sent first followed by the workspaces in RECEIVING

RELATED INFORMATION

Syntax: call_presentation(1), data_type_definition(1), presentation_procedure(1), task_definition(1), workspace(1) acmsxp_introduction(1)