The document provides an overview of the C programming language, detailing its development at AT&T's Bell Labs and key features such as identifiers, keywords, and data types. It explains the rules for naming identifiers and variables, emphasizing case sensitivity and restrictions on character usage. Additionally, it outlines how to declare and initialize variables in C, highlighting the structure and types involved.

2. • It had been developed at AT&T’s (American Telephone and
Telegraph)BellLaboratories in 1972 by DennisRitchie.
• It is based on highlevel language.

3. (Smallest individual unit in a program)
Data types
Keywords
Constants
Operators
Punctuators
Variables

4. • C identifier is a name used to identify a variable, function,
or any other user-defined item .
• An identifier starts with a letter A to Z, a to z, or an
underscore followed by zero or more letters, underscores,
and digits ( 0 to 9).
• C does not allow punctuation characters such as @, $, and
% within identifiers.
• For example : move name
• Zara a_122 _tem

5. • The name should consist of only alphabets (both upper
and lower case), digits and underscore sign (_)
• First character should be an alphabet or underscore.
• The name should not be a keyword.
• The uppercase and lowercase letters are considered
different as C is case-sensitive. For example : code ,
Code and CODE are three different identifiers.

6. • The words that are reserved for doing specific tasks and
have standard , predefined meaning in C are known as
keywords.
• They are always written in lowercase.
• There are only 32 keywords in C –
• Auto break case char const
• Continue default do double
goto
• Register enum switch long for
• Return int if else
struct
• While short void extern static

7. • A data type in a programming language is a set of data
with values having predefined characteristics such as
integers and characters.

8. Data Types
Primary/ Built-in Derived/ User-defined
double
Array
Floating-
point
character
Integer
String
pointer
Structure
Function

9. • A variable is nothing but a name given to a storage area
that our programs can manipulate.
• Each variable in C has a specific type, which determines
the size and layout of the variable’s memory.
• The range of values that can be stored within that
memory and the set of operations that can applied to the
variable.
• Rules for variable naming –
• Variable name can be composed of letters, digits, and underscore
character.
• It must begin with either a letter or an underscore.

10. • A variable declaration specifies a data type and contains a list of
one or more variables of that type as follows :
• type variable_list;
• Here, “type” must be valid C data type including char, int, float,
double, or any user-defined object; and “ variable_list ” may
consist of one or more identifier names separated by commas.
• Example of valid declaration are :
int i , k;
char ch;
float salary , f;
double d;
• Variables can be initialized ( assigned an initial value) in their declaration.
type variable_name= value ;
Example :int d=3,f==6;
• A variable declaration has its meaning at the time of compilation only, the
compiler needs actual variable declaration at the time of linking the program.