The document discusses key concepts of the C programming language including its history, structure, data types, variables, operators, input/output functions, and preprocessor directives. Specifically, it covers C's modular structure using functions, header files that enable code reuse, and the main function which acts as the program entry point. It also describes primitive, derived and user-defined data types in C as well as common constants, variables, and operators supported.

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3. History of ‘c’
Features of ‘c’
Structure of program
Header files
Main function
Data type
Constant
Variables
Operators
Input/output
C preprocessor
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 C is developed by Dennis Ritchie
 C is a structured programming language
 C supports functions that enables easy maintainability of
code, by breaking large file into smaller modules
 Comments in C provides easy readability
 C is a powerful language

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 Important feature of ‘C’ language is it is portable, by
portability we mean that the program can be run on any
hardware machine.
 It supports modular programming.
 It supports bit-wise operations.
 It is known as structured programming language.

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 Documentation Section //optional
 Link section //optional
 Defining section //optional
 Global declaration section //optional
 Main function section //Must
 {
 Declaration part
 Executable part.
 }
 Sub program section //optional
 Function 1
 Function 2
 .
 .
 Function n

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 The files that are specified in the include section is called as
header file
 These are precompiled files that has some functions defined in
them
 We can call those functions in our program by supplying
parameters
 Header file is given an extension .h
 C Source file is given an extension .c

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 This is the entry point of a program
 When a file is executed, the start point is the main function
 From main function the flow goes as per the programmers
choice.
 There may or may not be other functions written by user in a
program
 Main function is compulsory for any c program

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A data type in a programming language is a set
of data values having predefine characteristics.
there are three classes of data types:
Data Type
Primitive derived user define

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 Primitive data types
int, float, double, char
 Aggregate data types
Arrays come under this category
Arrays can contain collection of int or float or char or
double data
 User defined data types
Structures and enum fall under this category.

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 The ‘C’ language supports following types of
constants:
Numeric constants (5, 15, 3.6, -5.4 etc)
Non-numeric constants
 Character constants (‘B’ , ‘a’ , ‘?’ , ‘5’ , ‘+’ etc)
 String Constants (“Computer”, “XYZ”, “-5.4” etc)

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 a Bell
 b Back space
 f Form feed
 n New line
 r Carriage return
 t Horizontal tab
 v vertical tab
 ’ single quote
 ” Double quote
 ? Question Mark
 Backslash
 0 Null

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 Variables are the identifiers whose value changes as opposite
to constants.
 As variable is an identifier, all the rules for naming an
identifier applies to variables also.
 Should not be a reserved word like int etc..
 Should start with a letter or an underscore(_)
 Can contain letters, numbers or underscore.
 No other special characters are allowed including space
 Variable names are case sensitive
 A and a are different.

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 Arithmetic (+,-,*,/,%)
 Relational (<,>,<=,>=,==,!=)
 Logical (&&,||,!)
 Bitwise (&,|)
 Assignment (=)
 Compound assignment(+=,*=,-=,/=,%=,&=,|=)
 Shift (right shift >>, left shift <<)

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 Input
scanf(“%d”,&a);
Gets an integer value from the user and stores it under
the name “a”
 Output
printf(“%d”,a);
Prints the value present in variable a on the screen

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 All preprocessor directives begin with #
 Possible actions
Inclusion of other files
Definition of symbolic constants & macros
Conditional compilation of program code
Conditional compilation of preprocessor directives

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