C – Language History & Basics

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C – Language History & Basics

·  The C programming language was developed at Bell Laboratories in 1972 by Dennis Ritchie

·   C programming language features were derived from an earlier language called “B” (Basic Combined Programming Language – BCPL)

·     C language was invented for implementing UNIX operating system

·       In 1978, Dennis Ritchie and Brian Kernighan published the first edition,"The C Programming Language” and commonly known as K&R C

·  In 1983, the American National Standards Institute (ANSI) established a committee to provide a modern, comprehensive definition of C.The resulting definition, the ANSI standard, or “ANSI C”, was completed late 1988.

FEATURES OF C PROGRAMMING LANGUAGE:

Ø C language is one of the powerful language. Below are some of the features of C language.

·         Reliability

·         Portability

·         Flexibility

·         Interactivity

·         Modularity

·         Efficiency and Effectiveness

USES OF C PROGRAMMING LANGUAGE:

Ø The C programming language is used for developing system applications that forms a major portion of operating systems such as Windows, UNIX and Linux. Below are some examples of C being used.

·         Database systems

·         Graphics packages

·         Word processors

·         Spreadsheets

·         Operating system development

·         Compilers and Assemblers

·         Network drivers

·         Interpreters

                                 
     Levels of Programming Languages:

Ø There are 3 levels of programming languages. They are,

1.     Middle Level languages:
Middle level languages don’t provide all the built-in functions found in high level languages, but provides all building blocks that we need to produce the result we want. Examples: C, C++

2.     High Level languages:
High level languages provide almost everything that the programmer might need to do as already built into the language. Example: Java, Python

3.     Low Level languages:
Low level languages provides nothing other than access to the machines basic instruction set. Example: Assembler

     C LANGUAGE IS A STRUCTURED LANGUAGE:

Ø Structure oriented language:

·   In this type of language, large programs are divided into small programs called functions.

·         Prime focus is on functions and procedures that operate on the data.

·         Data moves freely around the systems from one function to another.

·         Program structure follows “Top Down Approach”.

·         Examples: C, Pascal, ALGOL and Modula-2.

Ø Object oriented language:

·         In this type of language, programs are divided into objects.

·     Prime focus is in the data that is being operated and not on the functions or procedures.

·         Data is hidden and cannot be accessed by external functions.

·         Program structure follows “Bottom UP Approach”.

·         Examples: C++, JAVA and C# (C sharp).

Ø Non structure oriented language:

· There is no specific structure for programming this language. Examples BASIC, COBOL, FORTRAN.

C PROGRAMMING BASICS TO WRITE A C PROGRAM:

Ø Below are few commands and syntax used in C programming to write a simple C program. Let’s see all the sections of a simple C program line by line.

C Basic commands	Explanation
#include<stdio.h>	This is a preprocessor command that includes standard input output header file(stdio.h) from the C library before compiling a C program
#include<conio.h>	This is a preprocessor command that includes console input output header file(conio.h) from the C library before compiling a C program
main()	This is the main function from where execution of any C program begins.
{         }	This indicates the beginning & ending of the main function.
/*_some comments_*/	whatever is given inside the command “/*   */” in any C program, won’t be considered for compilation and execution.
Clrscr()	This Is built-in-function which Clear the output screen before executing the program.
printf(“Hello World! “);	printf command prints the output onto the screen.
scanf(“string type”,& variable name);	This command Is used to get any data from the user.
getch();	This command waits for any character input from keyboard.
Eg. printf("Enter Number=");       scanf("%d",&a);	Here the printf statement will print "Enter Number=", Through scanf user can put the number.

       

    BASIC STRUCTURE OF A C PROGRAM:

Ø Structure of C program is defined by set of rules called protocol, to be followed by programmer while writing C program. All C programs are having sections/parts which are mentioned  below.

1.   Documentation section

2.   Link Section

3.   Definition Section

4.   Global declaration section

5.   Function prototype declaration section

6.   Main function

7.   User defined function definition section

Example OF Basic Structure Program:

/*     Documentation section     C programming basics & structure of C programs */ #include <stdio.h>     /* Link section */ int total = 0;             /* Global declaration, definition section */ int sum (int, int);    /* Function declaration section */ void main ()            /* Main function */ {      clrscr();     printf ("This is a C basic program \n");     total = sum (1, 1);     printf ("Sum of two numbers : %d \n", total);     getch(); } int sum (int a, int b) /* User defined function */ {       return a + b;      /* definition section */ }

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