2 Basic Concepts

The C language was initially designed as a small, portable programming language used to implement an operating system. In its history, C has evolved into a powerful tool for writing all types of programs, and includes mechanisms to achieve most programming goals. C offers:

• A standard set of lexical elements

• A wide variety of types for data objects, including:

  • Integer and floating-point constants and variables

  • Pointers to data locations in memory and the ability to do pointer arithmetic

  • Arrays of identically typed data

  • Structures and unions with members of different data types

• The ability to group independent code blocks into named functions

• A large set of operators used to form expressions, including bit-wise operators

• A simple method of declaring data objects and functions

• Several preprocessor directives to expand the functionality of the language

• Numerous library functions to handle many common programming tasks

• A high degree of portability

To help you take full advantage of C's features, the following sections provide a guide to the basic concepts of the language:

• Blocks (Section 2.1)

• Compilation units (Section 2.2)

• Scope (Section 2.3)

• Visibility (Section 2.4)

• Side effects and sequence points (Section 2.5)

• Incomplete type (Section 2.6)

• Compatible and composite types (Section 2.7)

• Linkage (Section 2.8)

• Storage classes (Section 2.10)

• Forward references (Section 2.11)

• Tags (Section 2.12)

• lvalues and rvalues (Section 2.13)

• Name spaces (Section 2.14)

• Preprocessing (Section 2.15)

• Type names (Section 2.16)

These sections represent an expanded glossary of selected C terms and basic concepts. Understanding these concepts will provide a good foundation for a working knowledge of C, and will help show the relationship of these concepts to more complex ones in the language.