设根结点的层次为0，则高度为K的二叉树的最大结点数为______

Email is the______of much organized exchange between groups of individuals．

E-checks require digital______and authentication services to digitally process information between the payer payee,and bank．

The suffixes com,org,edu,mil,and gov appearing in E-mail addresses stand for______,organization,educational,military,and governmental respectively．

The biggest category of information-based occupations is information______．

(65)

A(n)______ allows users to scramble and unscramble their messages easily without a third partyintruding．

Mc Call软件质量模型着重考虑了软件产品的三个侧面：软件的操作特性、软件易于移植的能力和适应新环境的能力，(50)和(51)分别是软件操作和软件转移这两个方面中重要的因素。

(64)

(63)

在下列程序代码中，若主程序调用f1(x)时，参数传递采用引用方式，在f1()中调用f2(y)，参数传递采用传值方式，则f1()的输出结果为(33)；若主程序调用f1(x)时，参数传递采用传值方式，在f1()中调用f2(Y)，参数传递采用引用方式，则f1()的输出结果为(34)。

(62)

(61)