C - Language Introduction

Introduction:

1. C – Language proposed by Dennis Richie in 1969 at AT&T Bell Labs.
2. It is an upgraded version of two earlier languages, called BCPL and B, which were also developed by Bell laboratories. 
3. It is called a structured oriented programming language.
4. C is the basic language in all programming languages.
5. It is used to create system applications like games, drivers, and so on.

Why C programming language is required?

• Before using c program, the program was written by assembly language i.e. Middle-level language.
• Assembly languages were fully instruction based language so if any error comes, we cannot be found easily.
• Because If one word has spelled a mistake in the program then it returns full program lines have error so we cannot find the exact error(i.e. error number is not displaying).
• In C program using function concept for overcoming the above problem.
• That means, it is used to find an exact error in the program and which block has an error.
• Because the function is used to divide the program into smaller subprograms.

        For example,

• The main() function have add(),sub() and mul() functions and one error in sub() block means C program easily identified and it checks only that blocks.
• So using the C program save the compile-time and also we can be reusable the function code, so it reduces the number of lines.
• This is the reasons for calling the C program as Function oriented programming language or Procedure oriented programming language.

Note:

• If you need more details about the programming language, low-level language, middle-level Language, and high-level language means click the below links to learn. 
• https://www.whereisstuff.com/2020/09/introductions-of-programming-language.html

The basic structure of C:

Syntax:

 //Command line
<Header files>
 Main function()
 {

      Variable declaration
      I/O operation
 }

Example:

 #include<stdio.h>
 #include <conio.h>
 void main() 
 { 
     int a,b,c;
     clrscr();
     printf("Enter a and b value : ");
     scanf("%d %d",&a,&b);
     c=a+b; 
     printf("\nAddition of a and b value is: %d",c); 
     getch(); 
}

Output:

Program explanation:

• # - it’s called pre-processor and used to replace the values in variables. 
• include - it's used to add header files and the user programs.
• stdio.h - standard input and output header file(it holds printf and scanf of library files).
• conio.h - stands for console input and output header file(used in old MS-DOS compilers to create text user interfaces and it holds clrscr() and getch() libraries).
• void main() - main part
• int – data type
• a,b,c – variables
• clrscr() – refresh output screen
• printf – used to display the user entered details
• scanf – used to get the value from the user and put into the memory location
• %d - format specifiers
• c=a+b – addition process and stored result in c variable
• getch() – used to hold the output screen and wait until the user gives any type of input(i.e until the user press any key)

Output process in the backend:

Output process explanation in the backend:

Step 1: Write source code that is your program (refer above example program)

Step 2: Pre-processor

For example, a and b value is 5 and 4 then pre-processor replace the values

scanf(“%d %d”,5,4);

Step 3: Complier (convert the English language to machine level language)

To check the error and convert machine-level code (i.e. 0’s and 1’s)

Step 4: Assembler

Used to convert machine level language to human-readable language. (0’s and 1’s to normal text)

Step 5: loader and linker

Adding header files and pre-processor program

Step 6: Final output

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