Interface Files

All ASTERIX applications require an interface for execution. It is used to create an easily adapted link between program variables and application execution by defining prompts, help messages, argument order and expected data type.

If such a file cannot be found in the same directory as the executable is located then the following error message will be issued.

!! Interface file for simple not found
!
!! DTASK_DCLTASK: failed to start parameter system SUBPAR__IFNF, failed to find
!     interface module

An interface file has the same name as the application, with a file extension of .ifl for an ASCII file or .ifc for a compiled binary file (see Starlink User Note 115, ADAM - Interface Module Reference Manual, for more information on this topic). The utility compifl is used to compile simple.ifl. When running the application either type of interface file is valid, but the compiled version ensures correct syntax.

Here is the interface file for simple (also available at the Birmingham FTP or WWW site);

INTERFACE SIMPLE
  PARAMETER INP
    POSITION 1
    TYPE 'LITERAL'
    PROMPT 'Dataset'
    HELP 'Enter the filename of an SDF data file'
  ENDPARAMETER
ENDINTERFACE

The various fields supplied are explained below;

• INTERFACE - The interface is defined for the application simple.

• PARAMETER - Its has only one possible parameter, which will be referenced through the name INP from within the code.

• POSITION - The value for INP can be supplied on the command line, in which case it must be the first argument given.

• TYPE - The argument type is of a LITERAL unquoted string.

• PROMPT - The string `Dataset' is used as a prompt.

• HELP - The given text is printed if the user enters ` ?'.