C++: The Complete Reference

Another important aspect of C is that it has only 32 keywords (27 from the
Kernighan and Ritchie de facto standard, and five added by the ANSI standardization
committee), which are the commands that make up the C language. High-level
languages typically have several times more keywords. As a comparison, consider
that most versions of BASIC have well over 100 keywords!
C Is a Structured Language
In your previous programming experience, you may have heard the term block-
structured applied to a computer language. Although the term block-structured
language does not strictly apply to C, C is commonly referred to simply as a
structured language. It has many similarities to other structured languages, such
as ALGOL, Pascal, and Modula-2.
The reason that C (and C++) is not, technically, a block-structured language is that
block-structured languages permit procedures or functions to be declared inside
other procedures or functions. Since C does not allow the creation of functions
within functions, it cannot formally be called block-structured.
The distinguishing feature of a structured language is compartmentalization of code
and data. This is the ability of a language to section off and hide from the rest of the
program all information and instructions necessary to perform a specific task. One
way that you achieve compartmentalization is by using subroutines that employ local
(temporary) variables. By using local variables, you can write subroutines so that the
events that occur within them cause no side effects in other parts of the program. This
capability makes it very easy for programs to share sections of code. If you develop
compartmentalized functions, you only need to know what a function does, not how it
does it. Remember, excessive use of global variables (variables known throughout the
entire program) may allow bugs to creep into a program by allowing unwanted side
effects. (Anyone who has programmed in standard BASIC is well aware of this
problem.)
The concept of compartmentalization is greatly expanded by C++. Specifically, in
C++, one part of your program may tightly control which other parts of your
program are allowed access.
A structured language allows you a variety of programming possibilities. It
directly supports several loop constructs, such as while, do-while, and for. In a
structured language, the use of goto is either prohibited or discouraged and is not the
common form of program control (as is the case in standard BASIC and traditional
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C + + : T h e C o m p l e t e R e f e r e n c e
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