C Lang notes.ppt

LANGUAGE
A language is a communication media
between two parties
Programming languages: A programming
language is a language used in writing
programs to direct processing steps to be
carried out by a computer.

Programming languages are
classified into 3 categories
1) Machine Language (or) Binary language
2. Assembly language
3) High level language

Machine level Language
 Machine code is the fundamental language of a computer
and is normally written as strings of binary 1’s and 0’s. The
circuitry of a computer is wired in such a way that it
immediately recognizes the machine language and converts
it into the electrical signals needed to run the computer.
 Programs written in machine language can be executed very
fast by the computer. This is mainly because the CPU
directly understands machine instructions and no translation
of the program is required.
 Advantages:- If we know this language we can directly
interact with the system, with out depending on any other
applications.

Assembly language
The language, which substitutes letters and symbols for
the numbers in the machine language program, is called
an assembly language or symbolic language. The
translator program that translates an assembly code into
the computer’s machine code is called assembler. The
assembler is a system program, which is supplied by the
computer manufacturer.
Advantages of Assembly language:
 Easier to understand and use
 Easy to locate and correct errors
 Easier to modify
 No worry about addresses
 Easily re locatable.

High level language
 Every instruction, which the programmer writes
in a high-level language, is translated into many
machine language instructions.
 While writing programs in any of the above
languages, a programmer has to remember all
the operation codes of the computer and now in
detail what each code does and how it affects the
various registers of the computers.
 These languages enable the programmer to write
instructions using English words and familiar
mathematical symbols.

Low level languages
They are machine dependent languages.
These are easily understood by computers.
The machine language and assembly
languages are examples of low level
languages.

Machine Languages
As the name implies, programming is done
at machine level. The vocabulary of
computer consists of only two words zero
and one. e.g., 10101011

Assembly Language
To overcome the drawbacks of the machine level
language, computer engineers developed new
programming language which uses symbolic
instructions. This symbolic instruction oriented
programming language is known as Assembly level
language.
E.g., ADD X,Y; Add the contents of y to x

Compiler Interpreter
1. Compiler converts all
statements at a time, if errors
are there, it displays all errors
as a list.
2. After Compiling the whole
program, if the program is
error free then it will execute
the program.
3. After Compilation, it creates
an executable file, using that
executable file we can run the
program any number of
times.
4. It is fast.
1. Interpreter converts line by
line, at the time of interpreting
any error is there, it displays
that error.
2. After interpreting the first line,
if it is error free then it will
execute that line.
3. It does not create any
executable file, every time we
need to interpret the program.
4. It is slow.
Differences between Compiler
and interpreter

 Programming : The art of writing instructions for
computer to solve the specific task is known as
programming. The output of programming is a
well defined set of instructions. This is called a
program.
 Algorithm
A sequence of language independent which may
be followed to solve a problem.
 Flowchart
Diagrammatic representation of step for solving
the given problem

Algorithm
Calculating area of a circle
1. Start
2. Input radius in cm
3. Calculate, area=3.14*(radius*radius)
4. Display
5. Stop

What is C?
C is a programming language developed
at AT & T’s Bell Laboratories of USA in
1972. It was designed and written by a
man named Dennies Ritche.

Features of C
 Portability and machine Independent.
 Fast program execution.
 An extendible language.
 It is a structured programming language.

Programming in C
Character Set of C
Program
C Tokens
1. Alphabets
2. Numeric Digits
3. Special Characters
1. Constants
2. Variables
3. Keywords
4. Identifiers
Instructions

Character set of the
C language
This indicates group of characters which are useful to
write the programming statements. It contains 3 parts.
 Alphabets: C language supports upper case letters
(A to Z), lower case letters from (a to z). But both
are different. C is a case sensitive language.
 Numeric digits: C language contains the numeric
digits from 0 to 9.
 Special Characters: The characters other than
alphabets and numeric digits are called as special
characters.

Constants
It is a quantity which does not change its
value during executing a program.
Types of C constants
1. primary constants
2. Secondary constants

Integer constants
Integer Constant: These are the numbers
without decimal point or exponent.
Ex:- int a=10;
Real Constants
Float constant: These are the numbers with
decimal point or exponent.
Ex:- float pie=3.14;

Character Constants
Single Character Constant: It is any one of
the single character enclosed in single
quotation.
Ex:- char ch=’a’;
char section=’b’;
String constant: Group of characters
enclosed with in double quotations.
Ex:- char name[20]= “Chandra”;
char nation[10]= “India”;

Variables
It is a name given to the memory location
which holds a particular data value that can
be change during the execution of the
program.
Variables are 4 types.
 Integer variables
 Float variables
 Single character variables
 String variables.

Local & global variables
1. Local variable - A variable declared inside a
function.
This variable can only be used in the function.
2. Global variable - A variable declared outside of
any functions.
This variable can be used anywhere in the
program.

Rules to write variable names
 It must not exceed 31 characters.
 A variable name includes alphabets and
numbers, but it must start with an alphabet.
 It cannot accept any special characters,
blank spaces except under score( _ ).
 It should not be a reserved word.

Identifiers
Identifiers are names given to various
program elements, such as variables,
functions and arrays.

key words(or)
Reserved words
Keywords are the words whose meaning
has already been explained to the C
compiler. The keywords cannot be used as
variable names.

auto
default
enum
if
short
switch
Volatile
const
continue
break
do
extern
int
signed
typedef
While
goto
return
case
double
float
long
sizeof
Union
struct
void
unsigned
char
else
for
register
static
There are 32 keywords available in C

Data types
Data type Range Bytes Format
signed char -128 to +127 1 %c
unsigned char 0 to 255 1 %c
short signed int -32,768 to +32,767 2 %d
short unsigned
int
0 to 65,535 2 %u
long signed int -2147483648 to
+2147483647
4 %ld
long unsigned int 0 to 4294967295 4 %lu
Float -3.4e38 to +3.4e38 4 %f
Double -1.7e308 to +1.7e308 8 %lf
long double -1.7e4932 to 1.7e4932 10 %lf

Input and Output functions
1. Formatted I/O functions
Input function – scanf()
Output function – printf()
2. Unformatted I/O functions
Input function – gets()
Output function – puts()

Formatted I/O functions
Output Function
printf( ): This function is used to display the
information on the screen. It displays the
variable values and the string values. This
function belongs to stdio.h.
Syntax: printf(“control_string” ,variable_list);

Examples:-
int a=10;
printf(“The value of a is %d”,a);
float pie=3.14;
printf(“The value of pie is %f”,pie);
char ch=‘A’;
printf(“Ch = %c”, ch);
char name[20]=“ORBIT”
printf(“Name = %s”, name);

Input function
scanf( ):- It is an input function, that is used
to accept the input from the keyboard(user)
at the time of executing a program. This
function belongs to stdio.h .
Syntax: scanf(“control_string”, variable_list);

Examples:-
int a;
scanf(“%d”, &a);
float b;
scanf(“%f”,&b);
char ch;
scanf(“%c”,&ch);
char name[20];
scanf(“%s”,name);

Unformatted I/O functions
Output function
puts()
This function is used to execute only string
values.
Syntax:- puts(string_variable);
Ex:- char name[20]=“ORBIT”;
puts(name);

Input function
gets()
This function is used to accept only string
values.
Syntax:- gets(string_variable);
Ex:- char name[20];
gets(name);

Writing C Programs
 A programmer uses a text editor to create or
modify files containing C code.
 Code is also known as source code.
 A file containing source code is called as source
file.
 After C source file has been created, the
programmer has to invoke C compiler in order
to execute (run) the program.

Structure of a C program
/* Comment line section */  Documentation
optional
# header file section  when we use
predefined functions
main( )
{
Declaration part;  To declare the
variables which are
used in the program
Initialization part;  To initialize i.e. giving
values to the variables
Execution part;  To execute as output
}

Comment Line Section
In order to give documentation for a
program comment line is includes. It is
enclosed in between a /* */ because in
the compilation process these lines are not
includes.
Comments are two types
Single line comment - // ------------
Multi line comment - /* -----------
-----------*/

Header file section
‘C’ program consists of predefined
functions for that reason we should
include the files in which they are
defined. Which are saved with .h as
extension.

Ex:- # include <stdio.h>
stdio.h stands for standard input
output . header file
# - It is used to tell the preprocessor to
get the header file to included in the
source code.
Include - it is used to include header file
specified in your source code.

 When we write our programs, there are libraries of
functions to help us so that we do not have to
write the same code over and over.
 Some of the functions are very complex and long.
Libraries of functions make it easier and faster to
write programs.
 Using the functions will also make it easier to learn
to write a program.
stdio.h

Main( )
 The compilation and the running process is done
with the help of Main( ). Every program must have
a function called main. This is where program
execution begins.
 main() is placed in the source code file as the first
function for readability.
 The parentheses following the reserved word
“main” indicate that it is a function.

Declaration part
This area is where we declare all the
variables which are used in the program.
Initialization part
Here, we give values to the declared
variables.
Executable part
The output is seen from the executable
part. By using output functions.

getch()
It is a predefined function available in <conio.h>
library which reads the character from the
keyboard without printing on the monitor.
getche()
library which reads the character from the
keyboard with printing on the monitor.
clrscr()
library which clears the previous contents of user
screen window.

Execution of C Program
Steps to be followed in writing and running a C program.
 Creation of Source Program
Create a C program code in Turbo C Editor.
 Compilation of the Program
Press Alt + F9 for compilation.
 Program Execution
In Turbo C environment, the RUN option will do the
compilation and execution of a program.
Press Ctrl + F9 for execution of the program.

Operators
 Arithmetic operators
 Relational operators
 Logical operators
 Assignment operators
 Increment or decrement operators
 Conditional operators
 Sizeof Operator
 Bitwise Operator

Arithmetic Operators
Arithmetic operators are used to perform
arithmetic operations like addition,
subtraction, multiplication, division and
remainder.
Operator Name Meaning Example
+ Plus Addition a+b
- Minus Subtraction a-b
* Asterisk Multiplication a*b
/ Slash Division a/b
% Modulator Reminder a%b

Relational operators
These operators are used to check the relation between
the values.
Note:- When we used relational operators the output is
seen in the form of 0 or 1. If the relation is true the output
will be in 1. If the relation is false the output will be 0.
Ex:- a=10
b=5
Operator Example Result
> a>b 1
< a<b 0
>= a>=b 1
<= a<=b 0
= = a==b 0
!= a!=b 1

Logical operators
logical operators are used to combine two
or more relational expressions. C language
contains 3 logical operators.
Operator Name
&& And
|| Or
! Not

&& : (And)
Statement:- When all arguments are true
then only the total condition is true. Any one
of the arguments is false the total condition
is false.
Expressinn1 && Expression2 Result
T T T
T F F
F T F
F F F
Truth table

|| : (Or)
Statement:- When one of the argument is
true the total condition is true. If all the
arguments are false then only the
condition is false.
Expression1 || Expression2 Result
T T T
T F T
F T T
F F F
Truth table

! (Not)
Statement:- This is the negative operator,
we can place the ‘not’ operator before any
one of the condition. It returns the opposite
result of the condition. i.e. It converts true
to false and false to true.
! expression result
T F
F T
Truth table

Assignment operator
C language contains equal to (=)
operator to assign a value or
expression into a variable.
Ex:- a=10;
b=a+10;

Increment and decrement
operators
1. Increment operator (+ +)
Increment operator is used to increase the value by 1.
 Pre Increment( ++a)
First the value will be incremented, and then the
new value will be executed.
Ex:- printf(“%d”,++a);
 Post Increment(a++)
First the value will be executed and then one value
will be incremented.
Ex:- printf(“%d”,a++);

2) Decrement operator ( - - )
Decrement operator is used to decrease the
value by 1.
 Pre Decrement (--a)
If the value is decreased before execution it is
called as pre decrement.
Ex:- printf(“%d”,--a);
 Post Decrement (a--)
If the value is decreased after the execution it is
called as post decrement.
Ex:- printf(“%d”,a--)

Conditional operators
C language contains conditional operators (?, : ). By
using conditional operators we can get the output in the
form of statements also. ? and : are called as
conditional or ternary operators.
Syn:- (condition) ? printf(“value 1”) : printf(“ value 2”);
Ex:- (a>b) ? printf(“a greater than b”):printf(“a is
less than b”);
If the condition is true then value1 will be executed, if
the condition is false then value2 will be executed.

Size of Operator
This operator is used to find memory size
of the variable or datatype.
Syntax:- sizeof(variable or datatype);

Complement operator (~)
It gives the ones complement of the
number.
 Add one to the given number
 Change it's sign

Bitwise operators
Bitwise operators compares internal binary
format of the number. These operators are
applicable in between integer variables only.
 Bitwise AND &
 Bitwise OR |
 Bitwise XOR ^
 Bitwise Left shift <<
 Bitwise Right shift >>

A B & | ^
----------------------------------------------
0 0 0 0 0
0 1 0 1 1
1 0 0 1 1
1 1 1 1 0
----------------------------------------------------
Ex:- int a=10,b=8,c;
c=a&b;
10 : 1 0 1 0
8 : 1 0 0 0
---------------------------
c : 1 0 0 0 Answer=8

c=a|b;
10 : 1 0 1 0
8 : 1 0 0 0
---------------------------
c : 1 0 1 0 Answer=10
c=a^b;
10 : 1 0 1 0
8 : 1 0 0 0
---------------------------
c : 0 0 1 0 Answer=2

Bitwise Left shift operator (<<)
Bitwise Left shift operator shifts the number of bits
toward left side specified number of times and fills
right side bit with zero.
Or
Multiply the given number by specified number of
powers of 2.
int a=10,b;
b=a<<1; a*2=10*2=20
b=a<<2; a*2*2=10*2*2=40
b=a<<3; a*2*2*2=10*2*2*2=80

Bitwise Right shift operator (>>)
Bitwise right shift operator shifts the number of bits
towards right side specified number of times and fills
left side bits with zero.
Or
Divide the given number by specified number of of
powers of 2.
int a=10,b;
b=a>>1; a/2=10/2=5
b=a>>2; a/(2*2)=10/(2*2)=2
b=a>>3; a/(2*2*2)=10/(2*2*2)=1

PRECEDENCE OF OPERATORS
(Arithmetic operators only)
Operator Description Associativity
*
/
%
+
-
Multiplication
Division
Modulo
Addition
Subtraction
Left to right
“
“
“
“

Conditional statements
The statements which are executed
according to some condition are called
as conditional statements.
They are 3 types
 If
 If-else
 Nested if-else

The If statement
Statement: This statement is used to perform
conditional operations.
Syntax:
if(condition)
{
statement;
}
If the condition is true then statement will be
executed. If the condition is false then it will not
execute statement.

Flow chart
if(condition)
Statement(s);
Next statements(if any)
False
True

If-else
The general form of if-else statement is…
Syntax:
if(condition)
{
statement1;
}
else
{
statement2;
}
If the condition is true then statement1 will be executed, if
the condition is false then statement2 Will be executed.

Flow chart
Statement(s);
Statement(s);
if(condition)
False
True

Nested if-else
When a series of conditions are involved, we can use more
than one if-else statement in nested form.
Syntax:
if (condition)
{
statements;
}
else if (condition)
{
statements;
}
else
{
statements;
}

Switch statement
It is used to execute one of the options from no. of options. It is
also called as multi branching statement.
Switch (expression)
{
case value:
statements;
case value:
statements;
default:
statements;
}
The expression value may be int or character type. The switch
statement evaluates the expression. It will select one of the cases
based on expression. It will execute default statements when no
case is selected.

Break statement
 This control statement can be used in loops and switch
statements.
 It is used to terminate the loop when a specified condition
is satisfied.
 The control comes out of the loop and the following
statements are executed.
 In switch statements, the control comes out of the switch
statements and the following statements are executed.

Switch case
Syntax: switch(expression)
{
case 1:
{
statement;
}
break;
case 2:
{
statement;
}
break;
default:
{
statement;
}
}

Flow chart
switch(expression)
Case 1:
Match ? Statement(s); break;
case 2:
case n:
default Statement/s;
Next statement

The exit( ) Function
 The exit( ) is a function in the standard
library of C.
 This function causes immediate
termination of the program and execution
control returns to the operating system.

Control Statements
Unconditional control statements:
 goto statement
 break statement
 continue statement
Looping/Repetitive/Iteration control statements:
 for statement
 while statement
 do-while statement

Goto statement
Syntax:
goto label;
.
.
label :
Statement(s);
This is an unconditional control statement to tell the
compiler from where the next statements has to be
executed.
In other words, program control directly Jumps to
some location in a program with the help of this
statement.

Continue statement
 This control statements are used in the
loops.
 During execution if a continue statement
is encountered all the following
statements will be terminated and the
control will go to the next iteration of the
loop without executing the following
statements in the loop.

Loop control structures
LOOPING:- The process of executing a
block of code repeatedly is called as looping.
They are 4 types
 For loop
 While loop
 Do while loop
 Nested for loops

All the four loops are used for same process but
there syntax is different.
All the four loops have 3 steps is common.
 Initialization:- It is the starting point of the loop
process.
 Condition:- In this step logical test is applied. It
is true the block of code is executed. Till the
condition fails.
 Increment / Decrement:- In order to proceed or
stop the loop increment or decrement is
required.

For loop
It is used to execute a set of statements
repeatedly as long as the given condition is true.
Syntax:-
for (initial value ; test condition ; increment /decrement)
{
statements; //body of for loop
}
Ex:- for(i=1; i<=10; i++)

For loop
Syntax:-
for (initial value ; test condition ; increment /decrement)
{
statements; //body of for loop
}
Ex:- for(i=1; i<=10; i++)
Initialization expression
Test expression
Body of the loop
Update expression
Next statements (if any)
False
True
Flow chart

While loop
Syntax:- while (condition)
{
statements; //body of while loop
}
First the condition is tested, if it is true the body of
the while loop will be executed first time, again
the control is transferred back to while loop and
checks the condition, If it is false the control will
come out of the while loop.

Flow chart
while
(condition)
Statement(s);
Next statements (if any)
False
True

Do While Loop
This statement executes a set of statements as
long as the condition is true.
Syntax: do
{
statements;
statements;
}
while(condition);
This is similar to while loop, but the difference is
this loop will execute the statements at least once.

Statement/s;
do
while
(condition);
True
Flow chart

Nested for loop
In order to get the output in the form of
rows and columns we use nested for
loops. If the outer loop condition is true
it enters into the inner loop. Till the
outer loop condition is false the looping
process is continued.

ARRAYS
An array is contiguous area in the memory
referred by a common name. The array allows
the storage of a number of data values in one
variable. Each array element i.e. each
individual data item is referred by specifying the
array name followed by one or more subscripts.
Each subscript is enclosed with square
brackets. Each subscript indicates the position
of the element in the array. Arrays are divided
into 2 types.
1. Single dimensional array or One dimensional
array
2. Two dimensional array

One dimensional array
The array which is using only 1 subscript is
known as one dimensional array. In one
dimensional array the elements are
represented in single row or single column.
Syntax:- Data_type variable_name[subscript]
Ex:- int a[5]={40, 50, 70,90,100};
Float b[4]={20.5, 40.9, 45.7, 23.8};
Char c[5]={‘O’,’R’,’B’,’I’,’T’};

Multi dimensional array
The array which is using two subscripts is known
as 2 – dimensional array
Syntax:-
Data_type variable_name [subscript][subscript]
Ex:- int a[2][2]={{1,2,},{3,4}};
The above declaration states that ‘a’ is an two
dimensional Array variable in which the values
are stored in 2 rows and in 2 columns

String Functions
A character array is defined as a string. A
group of characters is called a string. We
cannot handle with string same like integers
or real values. For example, if you want to
compare an integer value with another int
value. We can do that by using = =
operator. But the same procedure cannot
be applied for strings. In order to handle
with strings there are some string handling
functions.

Strlen( )
This function is used to find the length
of a string.
Syntax:- strlen(string);
Note:- When we are using string
functions we have to include a header
file <string.h>

Strcpy( )
This function copies a string from
one string variable to another string
variable.
Syntax:-
strcpy(target_string , source_string);

Strcat( ):- (String concatenation)
This function adds a string at the end
of another string
Syntax:- strcat(string1,stirng2);

Strcmp( ):- (String comparison)
This compares one string with
another string.
Syntax:-
strcmp(string1, string2);

Stricmp( )
This function is similar to strcmp, but
this function ignores the case
sensitivity.
Syntax:-
stricmp(string1, string2);

Strrev( )
This function reverses the given
string.
Syntax:- strrev(string);

Strupr( )
This function converts the given
string into upper case (capital letters)
Syntax:- strupr(string);

Strlwr( )
This function converts the given
string into lower case.
Syntax:- strlwr(string);

Single character
1) toupper( ) :- This function converts a single
character to upper case.
Syntax:- toupper(character);
2) tolower( ) :- This function converts a single
character to lower case.
Syntax:- tolower(character);
 Note:- when we are using single character
functions we have to include a header file
<ctype.h>

Functions
A function is a set of statements that
performs a specific task. Functions
are 2 types
1. Pre defined functions or Standard
functions
2. User defined functions

Pre defined Functions
These functions which are already
defined (in built) along with C are
called as pre defined functions.
Ex:-
printf( ), scanf( ), pow( ), strlen( ),
strcpy( ), toupper( ),……

User defined functions
These functions defined by the user in
order to work with complex program and
to develop the efficiency of the program
are called as user defined functions. In
order to define a function we have 3 types.
• Function definition
• Function prototype
• Invoking a function

Function definition
 Function heading
• Return type
• Function name
• Specification of parameters

a. Return type:- Return is called as data
type mention according to the type of
value returned from the function.
Note:- When there is no return statement
we should mention void as a default
return type.
b. Function name:- Here we mention the
name of a function. It is just like a
variable name

C. Specification of parameters:- The specify
the number of values are variables taken by
the called function from main program.
Note:-The parameters mentioned in the
main program for calling a function are
called as actual parameters.
The parameters mentioned in the function
which are received from the main program
are called formal parameters.

 Block of code
The code which is written with in the
braces of a function is called as block of
code.
 Return statement
This is the last statement of a function it is
to return a value from the user defined
function to the main program.

It is declared in the main program about the
function.
Note:- Function prototype is optional if the
function is defined before the main. It is
compulsory if the function is defined after
the main.
Function Prototype

Invoking a Function
From here we call the function. A
function as no live when it is not
Invoked.

Uses of functions
 Dividing the task into sub tasks.
 If a particular task is repeated number of times in a
program we can create a function and call that
function wherever we want.
 Whenever a function is called in a statement the
control will be transferred to that called function. After
executing all statements it returns back to the calling
function.
 The length of the source program will be reduced by
using functions at appropriate places.
 A function can be used in other programs also.

Syntax of a function / function definition
Return_type function_name (argument list)
{
declarations;
statements;
-------------
return value;
}
Function declaration
Return_type function_name (argument list);

Pointers
Pointer is a memory location or a variable which
stores the memory address of another variable in
memory
Pointers are much more commonly used in C &
C++ than in many other languages (such as
BASIC, Pascal, and certainly Java, which has no
pointers).

Problem solving using C++
What are pointers for?
Here are some common uses:
• Accessing array elements
• Passing arguments to a function when the
function needs to modify the original argument
• Passing arrays and strings to functions
• Obtaining memory from the system
• Creating data structures such as linked lists

Memory map
i
65524
‘i’ - Location name
10 - Value at location
65524 – Location number or address.
Declaration of a pointer:
Int a, *x;
Float b, *y;
Char c, *z;
Pointer variable is same as normal variable. But a *
symbol is added before the variable.
10

Usage of pointers
As pointers work with addresses accessing through
addresses first then through a normal variable. When
the values are called with the help of address by a
function the modifications done to the variables
shows the reflection.
Indirectly we can get the value of a variable by using
*. So * is called as indirection operator. Whatever the
data type may be a pointer variable occupies only 2
bytes of memory.

Parameter passing mechanism
 Call by value
 Call by address
 Call by value:- When the function calls the
parameters by taking values the modifications
done to the parameters by the function doesn’t
reflect.
 Call by address:- When the parameters are
called by address the changes done to the values
within the function shows the reflection.

Structures
Structure is a user defined data type. A structure is
a collection of variables that is referenced under a
single name. A structure contains a number of
data types grouped together. These data types
may or may not be of the same type.
Definition of a structure: - Structure is a
collection of variables which are of dissimilar data
types.

Declaring a structure:-
struct <structure name>
{
structure element 1;
structure element 2;
---
structure element n;
};
structure variable;

Ex:- struct book
{
int pages;
char author[20];
float price;
};
 In the above declaration book is called Tag
name and pages, author, price are called as
data members of the structure

Declaring a variable for a structure
Ex:- struct book b;
Here, ‘b’ is a variable of a structure to
which we can give 3 details.
The data members of the structure are
called by the variable using ( . ) operator.
For example:- b.pages
b.author
b.price

Features of a structure
With the help of structure we can maintain a
data in a systematic order. We can handle a
structure within a structure. And also we can
call the structure variable through functions
and Arrays also can be implemented
through structures. Pointer to structure is
also possible.

Unions
A union is similar to structure, but the difference is
1. The size of the structure variable is sum of all the
members size, but union size is the maximum
member's size.
2. In structure we can see all members at
a time, but in union we can see only one
member at a time because when we store
the second member, first value will be
over written.

Files
File is a collection of data to be stored
permanently in the disk space. The
disk may be either hard disk or floppy
disk or compact disk

Difference between Array and File
1.File is a collection of data. The data may be of
similar or dissimilar type.
Array is collection of elements of similar
datatype.
2. File size is unlimited.
Array size is limited.
3.File data is stored permanently in the disk
space.
Array data is stored temporarily in the RAM.

To Create a File pointer
FILE is a macro which is used to create
a file pointer which holds the address of
some file.
Syntax:- FILE * file_pointer;
Example:- FILE *fp;

To create or open the file
fopen()
It is a predefined function available in
<stdio.h> which is used to create or
open the file.
Syntax:-
file_pointer=fopen(filename,"Modes");

Modes are nothing but permissions to create
or open the file.There are 6 modes.
r:- fp=fopen(“Filename.extn","r");
If the file is already exist then it opens the
file with read permission.
r+ :- fp=fopen(“Filename.extn","r+");
file with read and write permission.

W :- fp=fopen(“Filename.extn","w");
file with write permission by deleting
previous data else creates the new file.
w+ :- fp=fopen(“Filename.extn","w+");
file with read and write permission else
creates the new file.

a :- fp=fopen(“Filename.extn","a");
If the file is already exist then it opens
the file with add permission else
creates the new file.
a+ :- fp=fopen(“Filename.extn","a+");
It creats or opens the file with read
write and append permission.

To close the file
fclose()
<stdio.h> which is used to close the
specified file.
Syntax
fclose(file_pointer);
Example
fclose(fp);

getchar()
getchar() is a macro that gets a character
from stdin
Syntax: - int getchar(void);
putchar()
putchar() is a macro that outputs a
character on stdout
Syntax: -int putchar(int c);

getc()
getc() is a macro that gets one character
from a stream
Syntax: - getc(file_pointer);
putc()
putc() is a macro that outputs a character
to a stream
Syntax: - putc(character, file_pointer);

fputs()
fputs copies the null-terminated string s to the
given output stream. It does not append a
newline character, and the terminating null
character is not copied.
Syntax: - fputs(character, file_pointer);
fgets()
fgets reads characters from stream into the
string. It stops when it reads either n - 1
characters or a newline character, whichever
comes first.
Syntax: - fgets(character, file_pointer);

To write the character into the file
fputc()
It is a predefined function available in <stdio.h>
which is used to write the specified character into
the file.
Syntax
fputc(charactervariable,file_pointer);
Example
char ch='A';
fputc(ch,fp);

To read the character from the file
fgetc()
which is used to read the character from file.
Syntax
charactervariable=fgetc(file_pointer);
Example
char ch;
ch=fgetc(fp);

To delete the file
remove()
<stdio.h> which is used to remove the
specified file.
Syntax
remove(filename);
Example
remove("Sachin");

To rename the file
rename()
<stdio.h> which is used to rename the file.
Syntax
rename(old filename,new file name);
Example
rename("Sachin","Mahesh");

To write the different types of data into the file
fprintf()
which is used to write the different types of data
into the file .
Syntax
fprintf(file_pointer,"formatspecifier",variable);
Example
char c='@';
int i=10;
float f=34.56
fprintf(fp,"%d%c%f",i,c,f);

To read the different types of data from the file
fscanf()
which is used to read the different types of data from
the file .
Syntax
fscanf(file_pointer,"formatspecifier",Address of
variable);
Example
char c;
int i;
float f;
fscanf(fp,"%d%c%f",&i,&c,&f);

storage classes
They are 4 types
1) automatic storage class
2) register storage class
3) static storage class
4) external storage class

Automatic storage class
The features of a variable defined to have an
automatic storage class are as under
 Storage : Memory
 Default initial value : Garbage value
 Scope : Local to block in which the variable is
defined
 Life : Till the control within the block in which
the variable is defined

Register storage class
 Storage : CPU registers
 Default initial value : Garbage value
 Scope : Local to block in which the
variable is defined
 Life : Till the control within the block in
which the variable is defined

Static storage class
 Default initial value : Zero
 Scope : Local to block in which the
variable is defined
 Life : Value of the persists between
different function calls

External storage class
 Default initial value : Zero
 Scope : Global
 Life : As long as the program execution
doesn't come to an end

C Lang notes.ppt

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C Lang notes.ppt