Chapter Summary
We have presented the essentials of data representation and numerical operations in digital computers. You should master the techniques described for base conversion and memorize the smaller hexadecimal and binary numbers. This knowledge will be beneficial to you as you study the remainder of this book. Your knowledge of hexadecimal coding will be useful if you are ever required to read a core (memory) dump after a system crash or if you do any serious work in the field of data communications.
You have also seen that floating-point numbers can produce significant errors when small errors are allowed to compound over iterative processes. There are various numerical techniques that can be used to control such errors. These techniques merit detailed study but are beyond the scope of this book.
You have learned that most computers use ASCII or EBCDIC to represent characters. It is generally of little value to memorize any of these codes in their entirety, but if you work with them frequently, you will find yourself learning a number of "key values" from which you can compute most of the others that you need.
Unicode is the default character set used by Java and recent versions of Windows. It is likely to replace EBCDIC and ASCII as the basic method of character representation in computer systems; however, the older codes will be with us for the foreseeable future, owing both to their economy and their pervasiveness.
Your knowledge of how bytes are stored on disks and tape will help you to understand many of the issues and problems relating to data storage. Your familiarity with error control methods will aid you in your study of both data storage and data communications. You will learn more about data storage in Chapter 7. Chapter 11 presents topics relating to data communications.
Error-detecting and correcting codes are used in virtually all facets of computing technology. Should the need arise, your understanding of the various error control methods will help you to make informed choices among the various options available. The method that you choose will depend on a number of factors including computational overhead and the capacity of the storage and transmission media available to you.
