1. Introduction to C Programming LanguageBy
Rajan Datt

2. Overview of C “C” strange name for programming language.
But this is one of the most popular language.
It is structured, high-level, machine independent language.
It allows software developer to develop program without worrying about hardware platforms.

3. Overview of C
1960: “ALGOL” - The root of all modern language was introduced.
1967: Martin Richards developed “BCPL” (Basic Combined Programming Language) primarily developed for system software.
1970: Ken Thompson developed language called “B” from BCPL.
“B” was used to create early versions of UNIX at Bell Laboratory.
BCPL and B, both were type-less language.

4. Overview of C
1972: “C” was developed from ALGOL, BCPL and B at Bell Laboratory by Dennis Ritchie.
C uses many concepts from these languages and added many new features including data types.
The UNIX itself was developed using C.
The rapid growth of C lead to many different versions, and some of them were often incompatible.
To assure that C lang. remains standard, American National Standard Institute appointed a committee to define a standard for C. The committee approved a version of C in 1989 which is now known as ANSI C. It was then approved by ISO in 1990.

5. Importance of C
Rich set of built in functions and operators can be used to write any complex program.
Program written in C are efficient and fast. For Exa. A program to increment a variable from in C lang. takes about 1 Second, while it takes almost 50 seconds in BASIC.
There are only 32 keywords in ANSI C, the strength of C lies in its functions.
C is highly portable: the programs written for one computer can be run on another compute easily.
C is well suited for structured programming. The modular structure makes program debugging, testing and maintenance easier.
Ability to extends itself: we can add our own function to C library.

6. First C Program
Let's see a simple program that prints out "Hello World" to standard out. We'll call our program as hello.c.
=========================================
#include <stdio.h>
main()
{ printf("Hello, world!\n"); return 0; }

7. Explanation of The Code
#include <stdio.h> -This line tells the compiler to include this header file for compilation.
What is header file?
They contain prototypes and other compiler/pre-processor directive.
Some common header files are stdio.h, stdlib.h and math.h.
main()- This is a special function of C, a starting point of a program
{ } - These curly braces state that "block begin" and "block end".
These can be used at many places,
printf() - This is the actual print statement which is used in our c program frequently.
return 0: we are trying to give something back through a program

8. An Improved Code
It is recommend that you should always document your program.
===============================================
#include <stdio.h>
/* Main Function * Purpose: Controls our program, prints Hello, World! * Input: None * Output: Returns Exit Status */ int main() { printf("Hello, world!\n"); return 0; }
/*…..*/ is the multi line comment.
/*…………/*…………..*/………..*/

9. An Improved Code
/* Sample program */ main() { printf( “I Like C \n'' ); exit ( 0 ); }
printf is the predefined standard C function.
C is case sensitive. In C, printf and PRINTF are not same.
All C statements should end with Semicolon(;) mark.
\n signifies newline.
exit() is also a standard function that causes the program to terminate. It is not needed here as it is the last line of main() and the program will terminate anyway.

10. Variables in C
Like most programming languages, C is able to use and process named variables and their contents.
Variables are simply names used to refer to some location in memory - a location that holds a value with which we are working.

11. Variables in C
Variables in C are the name given to memory locations. We use variables to store data in memory for later use
A variable must have to be declared before it can be used
You can declare Variables at the start of any block of code
Most local variables are destroyed on return from that function and created when the function is called
A declaration begins with the type, followed by the name of variable
int a; char b;

12. Keywords
auto, break, case, char, const, continue, default, do, double, else, enum, extern, float, for, goto, if, int, long, register, return, short, signed, sizeof, static, struct, switch, typedef, union, unsigned, void, volatile, while

13. Identifiers in C
Identifiers" or "symbols" are the names you supply for variables, types, labels, and functions in your program.
Identifier names must differ in case and spelling from any keywords.
You cannot use keywords as the identifiers; they are reserved for special use only.

14. Variable declarations
Variables are of three different types which are as follows:
Global Variable
Local Variable
Static Variable
Global Variable: Declare it outside of all the functions if you want to declare a global variable.
Local Variable: Inside the specific function that creates them. They are unknown to the other functions.
Static variables : In a local function scope, a static variable exists only, but it does not lose its value when program execution leaves this scope.

15. Basic types There are 4 basic types of variable in C; they are: char,
int,
double and
float

16. Overview of the C Operators
To create more complex expressions, variables and constants can be used in conjunction with C operators.
The C operators fall into the following categories:
Postfix operators, which follow a single operand only.
Unary prefix operators, which precede with a single operand.
Binary operators, which take two operands and perform a variety of logical and arithmetic operations.
The conditional operator (a ternary operator), which takes three operands and evaluates either the second or third expression, depending on the evaluation of the first expression only.
Assignment operators, which only assign a value to a variable.

17. Overview of the C Operators
The following tables describes different operators available in c
Operator Example  Meaning
() f()   Function call 
[]   a[10]   Array reference 
+ [binary] a+b
[binary] a-b
* [binary] a*b