c language learn chapter-1

What is c? 

it is a programming language
Commonly software is split into two types. They are
1. Language
2. Package.

What is package?

Example are ms-word, excel.

Packages are already predefined .That is if we want to format a paragraph there are icons in word software such as bold and italic by just clicking these icons we can format text. That is what should happen when we click bold icon is already predefined.

what is language

Opposite to it in programming language there will be set of statements. By executing these statements we can make solution to a problem. We can make packages using languages . that is what should happen in a package when events such as clicking a bold icon are defined through programming language.

We can also write operating system using languages like c.

What is an operating system?

Operating system is also software. It comes in the type of system software. This soft ware manages the system . i.e allocating memory to an application or setting priorities to software such as which should run first. It is also act as a interface between system and user. 

Examples for operating system are

1. Windows xp
2. Windows 7
3. Unix
4. Linux

In 1972 at bell laboratories, USA a research of developing UNIX operating system was going on. To write UNIX operating system they needed a language. So they were in the need of a programming language. So they developed c language. So the reason behind invention of c is to write UNIX operating system.

C is a portable language.

Why it is called as portable language?

A program written in c language in one platform can be run on another platform without change. So c is called as portable language.

C is powerful
C is structure oriented language.
C is not an object oriented programming language.
C can be used to write high level business applications. At the same time it can be used for low level assembly programs. As it can be used for both high level and low level programming it is called as middle level language.

Applications of c:

1. C is basic language for learning advanced languages like c++, java c#.
2. C is used in field of graphics
3. Used for creating system level programming. It is used for creating operating system, compilers.

What is a compiler?

Source code written in a programming language cannot be understood by system. There is an equal binary code for source code. The binary code contain only I’s and 0’s and it can be under stand by system. The role of compiler is to change source code in to machine language.
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CHAPTER-2 INTRODUCING PROGRAM IN C

We are going to write a program which will just display the output “hello world”.

The function for printing  on the console is printf function.(console  means monitor).

The following statement

Printf(“hello world”);

Will print the required output.

The  printf statement should be written with in main function as

Void main()

{

Printf(“hello world”);

}

The open curly brace marks the beginning of main function.

The closing curly brace marks the end of main     function.

Normaly  in c curly braces are used to mark the beginning and end of the block.

The block is a group of one or more sentences.

Now we are going to add one more statement at the beginning of the program.

#include<stdio.h>

Void main()

{

Printf(“hello world”);

}

The include statement includes the header file stdio.h

Stdio.h-> standard inputoutput.h

What is a header file.

Headers files  are files where the library functions are declared. Printf function is declared in stdio.h

In this programming if we didn’t include the include statement the compiler will show an error as printf function prototype missing.

Proto type refers to function declaration.

Now  save the program

Now compile the program.

The compiler will show an error if we did any syntax error in the program.

Syntax refers to the grammar of c language.

After correcting the error the program will get compiled.

That means the program will be converted into machine code.

Now run the program.

Now view the program output.

When we run the program second time or running any other program the program out put will be appended at the end of the previous programs output.

To avoid this we add another library function clrscr() which will clear the screen.

The clrscr() function needs the conio.h  header file to be included.

Conio.hà console input output.h

Now the program will be

#include<stdio.h>

#include<conio.h>

Void main()

{

Clrscr();

Printf(“hello world”);

}

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