精通COBOL编程指南
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"《 Beginning COBOL for Programmers》是一本专为程序员设计的COBOL编程入门书籍，旨在介绍这种历史悠久的高级编程语言。书中的内容涵盖了从基础到高级的COBOL知识，包括数据声明、程序逻辑控制、文件处理、字符串操作等多个方面，适合想要学习或转战COBOL编程的读者。"
COBOL，全称是Common Business Oriented Language，是一种面向业务的高级编程语言，与C、C#、Java、Pascal和BASIC等语言并列。它以其在商业领域的广泛应用和强大的数据处理能力而著称，尤其在金融、政府和企业系统中占据重要地位。这本书"Beginning COBOL for Programmers"针对已经有一定编程基础的读者，帮助他们快速理解和掌握COBOL语言。
书中详细介绍了各个章节的主题：
1. 第1章：COBOL简介，引导读者了解COBOL的历史、特点和其在现代软件开发中的角色。
2. 第2章：COBOL基础，讲解COBOL的基本语法结构和编程元素。
3. 第3章：COBOL中的数据声明，探讨如何定义和管理不同类型的变量和数据项。
4. 第4章：程序分段基础，介绍COBOL的Procedure Division，包括如何编写程序流程。
5. 第5章和第6章：控制结构，涉及选择（如IF-THEN-ELSE）和迭代（如PERFORM）语句，用于实现条件判断和循环。
6. 第7章和第8章：顺序文件的介绍和进阶，讲解如何读写和操作文件。
7. 第9章：编辑图片，讨论如何使用COBOL的Picture子句进行数据格式化。
8. 第10章：处理顺序文件的高级技巧，如文件的打开、关闭和错误处理。
9. 第11章：创建表格数据，介绍如何构建和管理二维数组。
10. 第12章：高级数据声明，深入探讨更复杂的数据类型和声明方式。
11. 第13章：搜索表格数据，讲解如何在表格中进行查找操作。
12. 第14章：排序和合并，介绍如何对数据进行排序和合并操作，以满足业务需求。
13. 第15章：字符串操作，涵盖字符串的处理函数和方法。
14. 第16章：创建大型系统，讨论COBOL在构建复杂系统时的设计和组织原则。
15. 第17章：直接访问文件，讲解如何使用索引和直接存取模式来提高文件访问效率。
16. 第18章：COBOL报告编写，介绍如何生成和定制COBOL应用程序的输出报告。
通过这些章节的学习，读者将能够掌握COBOL编程的基本技能，并具备解决实际业务问题的能力。此外，书中的实例和练习将有助于巩固理论知识，提升实际编程经验。对于任何想在IT行业中涉足COBOL的人来说，这本书都是一个宝贵的资源。
CHAPTER 1 ■ INTRODUCTION TO COBOL
12
clauses, sentences, sections, and divisions. As it happens, this design goal was not realized. Managers and users
nowadays do not read COBOL programs. Computer programs are just too complex for most nonprofessionals to
understand them, however familiar the syntactic elements. But the design goal and its effect on COBOL syntax had
one important side effect: it made COBOL the most readable, understandable, and self-documenting programming
language in use today. It also made it the most verbose.
It is easy for programmers unused to the business programming paradigm, where programming with a view to
ease of maintenance is very important, to dismiss the advantage of COBOL’s readability. Not only does this readability
generally assist the maintenance process, but the older a program gets, the more valuable readability becomes.
When programs are new, both the in-program comments and the external documentation accurately reflect
the program code. But over time, as more and more revisions are applied to the code, it gets out of step with the
documentation until the documentation is actually a hindrance to maintenance rather than a help. The self-
documenting nature of COBOL means this problem is not as severe with COBOL as it is with other languages.
Readers who are familiar with C, C++, or Java might want to consider how difficult it becomes to maintain
programs written in these languages. C programs you wrote yourself are difficult enough to understand when you
return to them six months later. Consider how much more difficult it would be to understand a program that was
written 15 years previously, by someone else, and which had since been amended and added to by so many others
that the documentation no longer accurately reflected the program code. This is a nightmare awaiting maintenance
programmers of the future, and it is already peeking over the horizon.
COBOL Is Stable
As a computer language, COBOL evolves with near-glacial slowness. The designers of COBOL do not jump on the
bandwagon of every new, popular fad. Changes incorporating new ideas are made to the language only when the new
idea has proven itself.
Since its creation in 1960, only four COBOL standards have been produced:
• ANS 68 COBOL: Resolved incompatibilities between different COBOL versions
• ANS 74 COBOL: Introduced the CALL verb and external subprograms
• ANS 85 COBOL: Introduced structured programming and internal subprograms
• ISO 2002 COBOL: Introduced object orientation to COBOL
Enterprises running mission-critical applications are unsurprisingly suspicious of change. Many of these
organizations stay one version behind the very slow leading edge of COBOL. It is only now that the 2002 version of
COBOL has been specified that many will start to move to the 1985 standard. This is one reason this book mainly
adheres to the ANS 85 standard.
Conscious of the long life of COBOL applications, backward compatibility has been a major concern of the
ANSI COBOL Committee. Very few language elements have been dropped from the language. As a result, programs I
wrote in the 1980s for the DEC VAX using VAX COBOL compile, with little or no alteration, on the Micro Focus Visual
COBOL compiler. Java, although only created in 1995, is now on its seventh version and already has a very long list of
obsolete, deprecated, and removed features. In the years since its creation, Java has removed more language features
than COBOL has in the whole of its 50-year history.
COBOL Is Simple
COBOL is a simple language (until the most recent version, it had no pointers, no user-defined functions, and no
user-defined types). It encourages a simple, straightforward programming style. Curiously enough, though, despite
its limitations, COBOL has proven itself well suited to its target problem domain (business computing). Most COBOL
programs operate in a domain where the program complexity lies in the business rules that have to be encoded rather
than in the sophistication of the data structures or algorithms required. In cases where sophisticated algorithms are
needed, COBOL usually meets the need with an appropriate verb such as SORT or SEARCH.
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