In this presentation you will get introduction about 'C' Language, its features, structure of C, constants, variables and data types.

1. Prepared By:
Aakash Singh
C
Language

2. INTRODUCTION
C language was evolved from ALGOL,BCPL
and B by Dennis Ritchie at bell laboratories in
1972.
 It has been developed to re-implement the
Unix operating system. It has since become one
of the most widely used programming
languages of all time.
To ensure that C language remains standard in
1983 American National Standards Institute
approved a version of c which is also referred to
as C89.

3. DENNIS RITCHIE
The c standardization
committee felt that a few
features of c++ and java if
added to c it would enhance
the usefulness of language.
The result was the 1999
standard for c .This version
is usually referred to as c99.

5. FEATURES OF C LANGUAGE:
It is a robust language and has a rich set of built
in functions .
C provides a wide range of data types ,
operators and functions which makes its code
highly efficient and fast.
C is a compatible language and can run on all
machines right from 8088 to recent machines.
C has only 32 keywords.

6. C is simple to implement and is highly effective.
C supports pointers which can directly access
the address of a variable in computers memory.
C provides Modular programming: It is a logical
collection of one or more functions or modules
C provides Dynamic Allocation of Memory :
This allows to allocate memory during runtime .
C is a middle level language.
C is extensible: It continuously adds the library
functions supported by c library.

8. STRUCTURE OF C PROGRAM
Documentation Section
Link Section
Definition Section
Global Declaration Section
main() Function Section
{
}
Subprogram Section:
Declaration part
Executable part
Function 1
Function 2
-
-
Function n

9. DOCUMENTATION SECTION:
It consists of a set of comment lines giving the
name of the program, the author and other
details, which the programmer would like to use
later.
LINK SECTION:
It provides instructions to the compiler to link
functions from the system library.
We include definite predefined standard library
functions in our C program and all these different
library functions are available in standard header
files.

10. DEFINITION SECTION:
Definition section defines all symbolic constants
like #define PI 3.14
GLOBAL DECLARATION SECTION:
It declares Global variables.This section also
declares user defined functions.
Global variables are the variables that are used in
more than one function and are declared in global
declaration section that is outside of all the
functions.
main() function section:
Every c program must have only one main
function. It indicates the beginning of program.

11. If the program contains more than one main
function the compiler cannot tell which one
marks the beginning of the program.
This section contains two parts:
Declaration part:
It declares all the variables used in executable
part.
Executable part :
There is only one statement in executable
part. It consists of statements which need to be
executed.
The program execution begins at opening
brace and ends at closing brace.

12. All statements in declaration and executable
part must end with semicolon i.e. ;.
Subprogram Section:
It contains all the user defined functions that
are called in the main function.
They are generally placed immediately after
main function although they may appear in any
order .

13. COMMENTS
Comments are used in the program to improve the
readability and understanding.
Comments are not executed by the compiler, they are
ignored by the compiler.
It helps the programmers to understand the various
operations of a program and serve as an aid to debugging
and testing.
Single line comments start with// symbol and multiple line
comments are written within /*and /*.

14. Header files
 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.

15. Constants
 Constants in
C are the
fixed values
that do not
change
during the
execution of
a program.

16. Constants Examples
 Integer Constants
o Refers to sequence of digits such as decimal integer, octal integer and
hexadecimal integer.
o Some of the examples are 112, 0551, 56579u, 0X2 etc.
 Real Constants
o The floating point constants such as 0.0083, -0.78, +67.89 etc.
 Single Character Constants
o A single char const contains a single character enclosed within a pair of
single quotes[ ‘ ‘ ]. For example, ‘g’, ‘a’, ‘I’ etc.
 String Constants
o A string constant is a sequence of characters enclosed in double quotes
[ “ “]; For example, “0211”, “Stack Overflow” etc.

17.  AVariables is a data name that is used to store any
data value.
 Variables are used to store values that can be changed
during the program execution.
 Variables in C have the same meaning as variables in
algebra.That is, they represent some unknown, or
variable, value.
x= a+b
z+2 = 3(y-5)
 Remember that variables in algebra are represented
by a single alphabetic character.
What Are Variables in C?

18.  Variables in C may be given representations containing multiple
characters. But there are rules for these representations.
 Variables names in C:
 May only consist of letters, digits, and underscores
 May be as long as you like, but only the first 31 characters are
significant
 May not be a C reserved word (keyword)
 Should start with a letter or an underscore(_)
 Can contain letters, numbers or underscore.
 No other special characters are allowed including
space.
Naming Variables

19.  Before using a variable , you must give the
compiler some information about the
variable; i.e., you must declare it.
 The declaration statement includes the data
type of the variable.
 Example of variable declarations:
int length;
float area;
Declaring Variables

20.  Variables are not automatically initialized. For
example, after declaration
int sum;
the value of the variable sum can be
anything (garbage).
 Thus, it is a good practice to initialize variables
when they are declared.
 Once a value has been placed in a variable it
stays there until the program alters it.
Declaring Variables

21. Data Types in C

22. Size and Range of Data Types
TYPE SIZE (Bits) Range
Char or Signed Char 8 -128 to 127
Unsigned Char 8 0 to 255
Int or Signed int 16 -32768 to 32767
Unsigned int 16 0 to 65535
Short int or Signed short
int
8 -128 to 127
Unsigned short int 8 0 to 255
Long int or signed long int 32 -2147483648 to
2147483647
Unsigned long int 32 0 to 4294967295
Float 32 3.4 e-38 to 3.4 e+38
Double 64 1.7 e-308 to 1.7 e+308
Long Double 80 3.4 e4932 to 3.4 e+4932