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'Software Science' revisited: rationalizing Halstead's system using dimensionless units



David W. Flater


The set of software metrics introduced by Maurice H. Halstead in the 1970's has seen much scrutiny and not infrequent criticism. This article takes a fresh look at these metrics using quantity calculus (the algebra of units) and a new approach to dimensionless units. In this way, it is possible to assign units to the major Halstead metrics in a manner that is logically consistent. However, Halstead's repurposing of counts of software attributes as counts of unobservable mental events leads to a less plausible, more confusing set of metrics for coding effort than for software attributes.
Technical Note (NIST TN) - 1990
Report Number


Flater, D. (2018), 'Software Science' revisited: rationalizing Halstead's system using dimensionless units, Technical Note (NIST TN), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed April 24, 2024)
Created May 9, 2018, Updated November 10, 2018