In [\textit{G. Cattaneo, M. Dalla Chiara, R. Giuntini} and \textit{R. Leporini}, An unsharp logic from quantum computation. Int. J. Theor. Phys. (in press)], the authors developed a new form of quantum logic (called \textit{quantum computational logic}) based on the theory of quantum computation. The present paper generalizes this work and expresses the semantics in terms of pure states on a commutative sequential effect algebra. This is an effect algebra \((E,0,1,\oplus)\) with a commutative associative operation \(\circ\) such that \(1\) is the neutral element of \(\circ\) and \(b\perp c\) implies \(a\circ(b\oplus c)=(a\circ b)\oplus(a\circ c)\). The author proves that the quantum computational logic is isomorphic to the standard commutative sequential effect algebra, i.e., to the real unit interval \([0,1]\), where \(\circ\) is the product and \(a\oplus b=a+b\) whenever \(a+b\leq1\).