难句解析：
①They give their owners automatic credit in stores, restaurants, and hotels, at home, across the country, and even abroad and they make many banking services available as well.
▲此句是由and连接的两个并列句，其中第一个句子结构较复杂，有一个复杂的地点状语in stores, restaurants, and hotels, at home, across the country, and even abroad，在阅读时在此处可以适当地加快速度。
△此句在理解中的难点是短语give somebody credit，此处credit应理解为“信用额度”，在英文中credit card意味着持卡人可以有一定的透支额度。
②Electronic cash registers can do much more than simply ring up sales. They can keep a wide range of records, including who sold what, when, and to whom.
▲这两个短句虽然简单，但是由于其中包含有几个短语，如do much more than...，ring up，electronic cash registers等，因此在阅读中也存在一定的障碍，在我们不知道一个短语的确切意思的情况下，通过上下文来定位其大致意思就显得非常重要。
△electronic cash registers意为“电子收银并记录”；do much more than的意思是“做的不只是”；ring up的意思可以从第一个短句的结构中推出，第一个短句的结构为A can do much more than simply B，我们知道A和B之间只存在程度上的差异，而本质相同，因此ring up应该与electronic cash registers意思相同或相近，应为“收款，记录”的意思。
③At the same time these computers record which hours are busiest and which employers are the most efficient, allowing personnel and staffing assignments to be made accordingly. And they also identify preferred customers for promotional campaigns.
▲在第一个句子中包含有两个并列宾语从句which hours are busiest and which employers are the most efficient，而在逗号后面的是一个分词结构，用来修饰主句。
△第一个句子中最后一个词accordingly和第二个句子中的preferred是理解的重点。accordingly意为“相应地”，而preferred是一个形容词，不是prefer的过去分词，意为“有优先权的，优先的”。
④Numerous other commercial enterprises, from theaters to magazine publishers, from gas and electric utilities to milk processors, bring better and more efficient services to consumers through the use of computers.
▲本句中的主语有一个非常长的修饰成分from theaters to magazine publishers, from gas and electric utilities to milk processors，在阅读的时候，如果我们注意到它只是在逗号之间的补充说明成分，我们就可以先跳过去抓句子的主干成分。

来源:可可英语 http://www.kekenet.com/kaoyan/201408/317068.shtml