This subroutine returns the name of a header item using an index of its relative position within a named source. By incrementing index N all the names in a source may be queried.

CALL HDR_NAME( PARAM, XNAME, N, ITEM, STATUS )

PARAM = CHARACTER $\ast$ ( $\ast$ ) (Given)

XNAME = CHARACTER $\ast$ ( $\ast$ ) (Given)

N = INTEGER (Given)

ITEM = CHARACTER $\ast$ ( $\ast$ ) (Returned)

STATUS = INTEGER (Given and Returned)

• This subroutine will directly access an image if an association has not already been made. Note that it will be opened for read-only access and you will not be able to write or delete any header items. If you need to be able to do this then access the image first, either with one of the ??x]]IMG_MOD[n][x] subroutines (if you intend to process the image data), or the HDR_MOD subroutine.

• The order in which header item names are returned may change if the source is modified (by deletion or by writing).

• The header item name will be returned in a hierarchical format if necessary.

• The total number of items from a source can be found using HDR_NUMB.