C language Notes [By:G.T. Chandrasekhar]

C LANGUAGE NOTES

G T CHANDRASEKHAR

Email Address: gtcsekhar@yahoo.com

some Important C Programmes

Some words about Computer Programming languages
Naturally a language is the source of communication between two persons, and also between person to machine like computer. The languages we can use to communicate with the computer are known as Computer programming languages.

Generally there are two major types of languages are available are as follows:

Low level languages
The set of commands available in low level is complex and not easy to understandable. In this category " Assembly " and " machine codes " are available. Assembly programs are faster than other high-level language programs.
High level languages

The set of commands available in high level language is very simple and easy to understandable.

High level languages are further divided into two major categories.

Procedure Oriented language
In this category we are able to create our project or programs using procedural approach means in this type we can able to divide our big project/program into small subroutines or procedures. After making procedures we can able to call a ‘procedure’ one or more places.
The lists of procedural languages are as follows:

C language

C++ (Object Oriented)

Java (Objected Oriented)

Smalltalk (Objected Oriented)

Pascal language
Non-Procedural Languages: This category also known as ‘Problem Oriented languages’. In this type of languages we can able to make program only at specific range like database. The followings are the examples of Non procedural languages

1. SQL (Structured Query Language)
2. SNOBOL (String processor)

C LanguageHistory

Developed at Bell Laboratories. first standard version release in 1972.
Developed by Dennis Richee.
Before c a Programming language is very popular in those days the name of the language is B-Language so the developers decided the name of ‘C’ language because C is next to B.

The Integrated Development Environment (IDE):

Turbo c features as integrated Development environment, or IDE,. It is also referred to as the programmer’s platform.) in IDE you can able to write/save/open your programs or code, compile using short cut keys, and also perform code debugging very easily.

IDE

Common Short cut Keys Description

F2 press to Save current work

F3 press to open an existing file

ALT-F3 press to close current

ALT-F9 press to compile only

ALT-F5 press to view the desired output of the program.

CTRL-F9 press to compile+run

ALT-X or ALT-F-X press to exit from TC IDE

C Programs Skeleton (General)

< Global Variable (on your demand)>

main () (Necessary)

{ statements }

< function definition>

{ }

Remember Some common rules for writing C program

Use all commands or statements in lower or small case.
After completion of a statement excluding main() or loops must insert ; (semicolon) as a statement terminator.
Don’t use/declare identifier or variable name same as statement name suppose int include; this is a wrong statement because include has a special meaning in the language.

Header Files or Preprocessor Directives contains references or links of library functions. That is built-in in the C language.

Suppose if you want to use a function clrscr() ; in the main function so must be declared on top # include <conio.h> other wise you could have an prototype error.

Some header files are as follows

Stdio.h

Conio.h

Dos.h

String.h

Stdlib.h

And many more header files are available in C…

void main(void)

Every C programs consists of one or more functions. No matter how many

functions there are in a C program , main is the one to which control is passed

from the operating system when the program is run ; it is the first function

executed. The word "void" preceding "main" specifies that the function main()

will not return a value. The second "void," in parenthesis , specifies that the

function takes no arguments.

printf()

printf() is built-in function we can display with printf() any message, variable

value on screen/file/printer.

In printf() we can use many escape sequences and format specifies.

Escape sequences are special notations through which we can display our data

Variety of ways:

Some escape sequences and their functions are as follows:

Escape Sequence	Description	Example
\n	Perform line feed & Carriage return operation	printf("A\nB");
\t	Prints a tab sequence on screen	printf ("A\tb");
\’	Prints a single quote character on screen	printf ("\’a\’");
\"	Prints a double quote character on Screen	printf ("\"a\"");
\r	Perform carriage return operation	printf ("a\rb")
\b	Remove one character from left	printf ("a\bHi!" );

Example Program #1

#include <stdio.h>

#include <conio.h>

void main(void)

{

printf( " Example Program (Escape Sequence) \n");

printf( " -----------------------------------------------\n");

printf( "Escape sequnce \t Meaning\n");

printf( " -------------------------------------------------\n");

printf(" \\\\ \t \\" \n");

printf(" \\\’ \t \’ \n");

printf(" \\\" \t \" \n");

printf(" \\n \t line feed & carriage return\n ");

printf(" \\t \t Tab characters or eigth spaces\n");

printf(" \\b \t Erase one char from right to left\n");

printf(" \\r \t perform only line feed\n");

getch();

}

This program produces following output

Example Program (Escape Sequence)

--------------------------------------------

Escape Sequence Meaning

------------------------------------------

\\ \

\’ ‘

\" \"

\n line feed & carriage return

\t Tab Characters or eight spaces

\b Erase one char from right to left

\r perform only line feed

Example Program #2

#include <stdio.h>

#include <conio.h>

void main(void)

{

clrscr();

printf( " \" I LOVE INDIA \" \n");

getch();

}

This program produces following output

" I LOVE INDIA"

Description : in the above we use a escape sequence \" this will produce " on screen after that a messageINDIA ZindaBad is appear after the message another " ( double quotation) appear on screen because of \"

Variable : variables are named peace of memory in which we can store our data and manipulate our data. Variables are used so that same space in memory can hold different values at different times.

In C language following are the list of data type available through which we can define our variables:

int (Example :int a,b,c)
float(Example:float pi;)
char(Example :char opt;)
long(long bigval;)
double(double bigval;)

Data Types Range Memory occupy

int -32768 to +32767 without fractional) 2 bytes

unsigned int 0 to 65,535 2 bytes

char -128 to 127 1 byte

char 0 to 256 1 byte

enum -32768 to 32,767 2 bytes

float 3.4 * (10**-38) 4 bytes

double 1.7 * (10**-308) 8 bytes

long double 3.4 * (10**-4932) 10 bytes

Format specifies are use when we want to display a variable value: