Halstead complexity measures

• ${\displaystyle n1}$ = the number of distinct operators
• ${\displaystyle n2}$ = the number of distinct operands
• ${\displaystyle N1}$ = the total number of operators
• ${\displaystyle N2}$ = the total number of operands

From these numbers, five measures are derived:

• Program length: ${\displaystyle N=N1+N2\,}$
• Program vocabulary: ${\displaystyle n=n1+n2\,}$
• Volume: ${\displaystyle V=N*(LOG2n)\,}$
• Difficulty : ${\displaystyle D=(n1/2)*(N2/n2)\,}$
• Effort: ${\displaystyle E=D*V\,}$

• Number of the used different operators ((${\displaystyle n_{1}}$) and operand (${\displaystyle n_{2}}$), ), together the vocabulary size ${\displaystyle n}$.
• Number of the altogether used operators (${\displaystyle N_{1}}$) and operand (${\displaystyle N_{2}}$), together the implementation length ${\displaystyle N}$.

From this then the sizes of Halstead length become (${\displaystyle HL}$) and Healstead volume (${\displaystyle HV=V}$) are calculated:

• ${\displaystyle HL=n_{1}\times \log _{2}n_{1}-n_{2}\times \log _{2}n_{2}}$
• ${\displaystyle HV=N\times \log _{2}n}$

From the base quantities one can compute different characteristic numbers, e.g.:

• ${\displaystyle D={n_{1} \over 2}\times {N_{2} \over n_{2}}}$

Where D = difficulty of the program to write or understand, e.g. with one Code review (?).

From http://www.sei.cmu.edu/str/descriptions/halstead.html [1] and the German wikipedia entry.

see also

• Function point
• http://de.wikipedia.org/wiki/Halstead-Metrik [2]
• Cyclomatic complexity