VPN主要采用了4项技术来保证安全。它们是加密技术密钥管理技术，身分认证技术和______。

The high-speed data services for the interconnection of computer networks are usually referred to as ______ connections．

A(n) ______ document is an interlinked system of documents in which a user may iump from one document to another in a nonlinear,associative way．

The most common query language is______．

E-mail is a(n) ______ message delivery system that allows information such as typed messages and multimedia to be sent to individual compmer users．

Information engineering emphasizes a modeling tool called ______ relationship diagrams．

在下列程序代码中，函数init()和plus()的定义如下图所示，若a和x以引用方式传递信息，则函数init的返回值为(34)；若a和x以传值方式传递信息，则函数。init的返回值为(35)。

(67)

(68)

(66)

编译程序的工作可分为6个阶段：词法分析、语法分析、(29)、中间代码生成、代码优化和目标代码生成。其中，中间代码生成和(30)不是必须经过的阶段。

(65)

(64)