Metrics for Source Code

Halstead assigned quantitative laws to the development of computer software, using a set of primitive measures that may be derived after code is generated or estimated once design is complete. The measures are :

n1 = the number of distinct operators
n2 = the number of distinct operands
N1 = the total number of operator occurrences
N2 = the total number of operand occurrences
Length: N = n1log2n1 + n2log2n2
Volume: V = Nlog2(n1 + n2)

SUBROUTINE SORT (X,N)
DIMENSION X(N)
IF (N.LT.2) RETURN
DO 20 I=2,N
DO 10 J=1,I
IF (X(I).GE.X(J) GO TO 10
SAVE = X(I)
X(I) = X(J)
X(J) = SAVE
10 CONTINUE
20 CONTINUE
RETURN
END

OPERATOR COUNT
1 END OF STATEMENT 7
2 ARRAY SUBSCRIPT 6
3 = 5
4 IF( ) 2
5 DO 2
6 , 2
7 END OF PROGRAM 1
8 .LT. 1
9 .GE. 1
10 GO TO 10 1
n1 = 10 N1 = 28
n2 = 7 N2 = 22