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Next Page: 4.1 A New Data Type: char
So far we have considered only numeric processing, i.e. processing of numeric data represented as integer and floating point types. Humans also use computers to manipulate data that is not numeric such as the symbols used to represent alphabetic letters, digits, punctuation marks, etc. These symbols have a standard meaning to us, and we use them to represent (English) text. In the computer, the symbols used to store and process text are called characters and C provides a data type, char, for these objects. In addition, communication between humans and computers is in the form of character symbols; i.e. all data typed at a keyboard and written on a screen is a sequence of character symbols. The functions scanf() and printf() perform the tasks of converting between the internal form that the machine understands and the external form that humans understand.
In this chapter, we will discuss character processing showing how characters are represented in computers and the operations provided to manipulate character data. We will develop programs to process text to change it from lower case to upper case, separate text into individual words, count words and lines in text, and so forth. In the process, we will present several new control constructs of the C language, describe user interfaces in programs, and discuss input/output of character data.