Source Code : Overview Of C Language

Overview Of C

C is developed by Dennis Ritchie

Developed between 1969 and 1973 along with Unix

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

Designed for systems programming

Operating systems

Utility programs

Compilers

Filters

Currently, the most commonly-used language for embedded systems

“High-level assembly�

Easy-to-understand compilation

Header files and Void main() function

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

#include

void main()

{

printf(“Hello, world!\n�);

}

-Preprocessor used to share information among source files

-Program mostly a collection of functions

“main� function special: the entry point

“void� qualifier indicates function does not return anything

Main function

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

Running a C Program

Compile the program – This will generate an exe file (executable)

Run the program (Actually the exe created out of compilation will run and not the .c file)

In different compiler we have different option for compiling and running. We give only the concepts.

Comments in C

Single line comment

// (double slash)

Termination of comment is by pressing enter key

Multi line comment

/*….

…….*/

This can span over to multiple lines

Data types in C

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.

Variables

Variables are data that will keep on changing

Declaration

<> <>;

int a;

Definition

<>=<>;

a=10;  or  int a=10;

Usage

<>

a=a+1;  //increments the value of a by 1

Variable names- Rules

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.

Variable Type

C has the following simple data types:

C Type	Size(Bytes)	Lower Bound	Upper Bound
char	1	-	-
unsigned char	1	0	255
short int	2	-32768	+32767
unsigned short int	2	0	65536
long int	4	-231	+231-1
float	4	-3.2*10+-38	+3.2*10+-38
double	8	-1.7*10+-308	+1.7*10+-308

Input and Output

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

Format specifiers

%d is the format specifier. This informs to the compiler that the incoming value is an integer value.

Other data types can be specified as follows:

%c – character

%f – float

%lf – double

%s – character array (string)

Printf and scanf are defined under the header file stdio.h

Operators

Arithmetic (+,-,*,/,%)

Relational (<,>,<=,>=,==,!=)

Logical (&&,||,!)

Bitwise (&,|)

Assignment (=)

Compound assignment(+=,*=,-=,/=,%=,&=,|=)

Shift (right shift >>, left shift <<)