BASICS OF C LANGUAGE

Start Learning:

As a matter of fact any language whether it is natural language (like Hindi, English, French, etc) or computer programming language, one has to learn basic constituents first.

For example alphabets are basic constituents of English language.

In a similar fashion we have to learn basic constituents of C language.

The order of our journey contains:

   Basic letters à Identifiers à Instructions  à Program

Basic Letters: 

Language writing includes letters as:

  Alphabets: a to z and A to Z

  Digits:   0 to 9

  Special Symbols:  +,%,*, &, “, >, ?, \, :, ;, -, ^ ,{, [, ),  etc

Identifiers:

Identifiers are smallest unit in the program that has some meaning. We know that compiler will be reading our source code to translate it in object code. So compiler should know about all the words of our program. Few words are predefined to compiler and rest need to be declared by the programmer. These words are identifiers as they can be identified by compiler.

Identifier includes constants, variables, keywords, macros, function name etc.

Here we are going to understand three of these; they are constants, variables and keywords.

Constant:

Software is developed to handle information. This information is called constant. Sometimes it is termed as data.

Constants can be categorized as Primary and secondary constants

Primary constants:

 Primary constants are also known as fundamental constants or basic constants. They are of three types; Integer constant, Real constant, Character constant.

  All numbers without decimal point involved in it are integer constants.

For example: 35, -20, 0, 123 etc

  All numbers with decimal point involved in it are real constant.

For example: 3.14, -43.56, 3.0 etc

  All character symbols are character constants if they are enclosed in single quotes and of unit length.

For example: ‘A’, ‘b’, ‘+’, ‘3’, ‘ ‘

Secondary constants:

Secondary constants are also known as derived constants, as they are derived from primary constants.

Arrays, strings, pointers, structures, union, enumerators are secondary constants.

We will see them in great detail in later chapters.

Variables:

Variables are the name of memory locations where we store our data. When C program is under execution, operating system allocates memory to store instructions of the program and also allocates space to store data.

Programmer has to decide how much space he is required with to store data. He also specifies the names of memory blocks in his program code.  These names are called variables.

We can change its value according to programming requirement.

Variable name may contain alphabets, digits or underscore.

No other symbol is allowed.

A valid variable name never starts with digit.

Keywords: 

Keywords are predefined words. They are also known as reserved words. Their meaning is known to the compiler.

ANSI (American National Standards Institute) announces 32 keywords in C language, but it may vary with compilers.

Keywords are predefined and we will see their meaning in subsequent chapters.

Here is the list of keywords:

auto     break   case     char     continue          const    do        default

double else      enum   extern for                   float     far        goto     

huge    int        if          long     near                 return   register            short

static    struct   signed union   unsigned          void     volatile            while

These keywords can not be used as variable or function names as they already have some meaning known to compiler.

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