Introduction

C is a general-purpose programming language, and is used for writing programs in many different domains, such as operating systems, numerical computing, graphical applications, etc. It is a small language, with just 32 keywords. It provides “high-level” structured programming constructs such as statement grouping, decision making, and looping, as well as “low level” capabilities such as the ability to manipulate bytes and addresses. 

1. C provides no operations to deal directly with composite objects such as lists or arrays. 
2. There are no memory management facilities apart from static definition and stack-allocation of local variables. 
3. And there are no input/output facilities, such as for printing to the screen or writing to a file.

Much of the functionality of C is provided by way  of software routines called functions. The language is accompanied by a standard library of functions that provide a collection of commonly used operations. 

• For example, the standard function printf() prints text to the screen (or, more precisely, to standard output—which is typically the screen). The standard library will be used extensively throughout this text; it is important to avoid writing your own code when a correct and portable implementation already exists.