  Software now lies at the heart of scholarly research. Here we argue that as
well as being important from a methodological perspective, software should, in
many instances, be recognised as an output of research, equivalent to an
academic paper. The article discusses the different roles that software may
play in research and highlights the relationship between software and research
sustainability and reproducibility. It describes the challenges associated with
the processes of citing and reviewing software, which differ from those used
for papers. We conclude that whilst software outputs do not necessarily fit
comfortably within the current publication model, there is a great deal of
positive work underway that is likely to make an impact in addressing this.
