### 1 Introduction

One of the most popular features of the ADAM environment is the Hierarchical Data System (HDS) (described in SUN/92nd SG/4). HDS enables associated data items to be stored together in a single file and in a structured fashion. HDS is also highly flexible, allowing a myriad of ways to organise your data. So HDS is jolly useful, but it does have one drawback—you cannot just type or print an HDS file to see its contents—you must run a programme. Obviously, you (or your friendly programmer) could write some code to list a particular structure, but this would be inefficient given the number of structures that are already in use, let alone the ones to come. What is required is a single utility that lists the contents of an HDS data structure to your terminal and, optionally, to a file for printing or documentation. This is where Hdstrace comes in handy.

Hdstrace lists recursively the name, data type, and values of an HDS structure or object. The type is bracketed by $<>$ to distinguish it from the name (cf. SGP/38). Indentation delineates structures. The format of the output is flexible; and more importantly, you can now always see the data values—something that was often impossible with original version. You control the formatting by specifying optional parameters on the command line, otherwise they have sensible defaults.