C programming

C Programming
Updated on:
03 August 2015
First published on 3 July 2012
This is the 7h Revised edition

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C Programming
DISCLAIMER
 The data in the tutorials is supposed to be one for reference.
 We have made sure that maximum errors have been
rectified. Inspite of that, we (ECTI and the authors) take no
responsibility in any errors in the data.
 The programs given in the tutorials have been prepared on,
and for the IDE Microsoft Visual Studio 2013.
 To use the programs on any other IDE, some changes might
be required.
 The student must take note of that.

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C Programming
History of C Programming
 C Programming Language was introduced by Mr. Dennis
Ritchie in 1972. He invented this language for the internal use
of AT & T Bell Labs. But due to the features of C Programming
Language it became very popular.
 Problems with languages existing before C –
 They were categorized in Lower Level Languages and Higher Level
Languages. The Lower Level Languages were designed to give better
machine efficiency, i.e. faster program execution. The Higher Level
Languages were designed to give better programming efficiency i.e.
faster program development.
 The languages before C were Application Specific e.g. FORTRAN
(FORmula TRANslation) was built for Engineering Applications
Development, COBOL (COmmon Business Oriented Language) was
developed for Commercial Application Development.

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C Programming
History of C Programming
 Dennis Ritchie thought about giving features of both Lower
Level Languages and Higher Level Languages. So he
introduced the concept of Compilers in C. The function of
compiler is to "Convert the code from Human Readable
Language to Machine Readable Language and Vice-a-Versa".

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C Programming
Basics of C Programming
Alphabets Words Sentences Paragraph
Steps in Learning English Language:
Alphabets
Numbers
Special Symbols
Constants
Variables
Keywords
Instructions C Program
Steps in Learning C Language:

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C Programming
'C' Alphabets:
Alphabets
A, B, ……, Y, Z
a, b, ……..., y, z
Numbers 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
Special Symbols ~ ' @ # % ^ & ( ) _ - + | { } [ ] : ; " ' <
> , . ? /

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C Programming
'C' Constants:
 A constant is an entity that never changes. There are two type of C
Constants – Primary Constants, Secondary Constants.
C Constants
Primary
Constants
Integer
Real
Character
Secondary
Constants
Array
Pointer
Structure
etc.

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C Programming
 Rules for Constructing Integer Constants:
 An Integer Constant must have at least one digit.
 It must not have a decimal point.
 It can be either positive or negative.
 If no sign precedes an Integer Constant, it is assumed to be positive.
 No commas or blanks are allowed in integer constant.
 The allowable range is: -2,14,74,83,648 to 2,14,74,83,647.
 Rules for Constructing Real Constants:
 A Real Constant must have at least one digit.
 It must have at least one decimal point.
 It can be either positive or negative.
 Default sign is positive.
 No commas or blanks are allowed within Real Constants.
 It's range is: 3.4e-38 to 3.4e38.

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C Programming
 Rules for Constructing Character Constants:
 A character constant is a single alphabet, a single digit or a
single special symbol enclosed within single inverted
commas. Both the inverted commas should point to the
left.
'C' Variables:
 An entity that may vary during the program execution is
called as Variable.
 Variable names are names given to the memory locations.
 These locations can hold integer, real or character constants.
 The integer variable needs 4 bytes, float variable needs
4 bytes, double variable needs 8 bytes and char variable
needs 1 byte memory space.

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C Programming
 Rules for Constructing a Variable Name:
 The variable name should not exceed 30 characters. Some
compilers allow variable names upto 247 characters. But
restrict variable name, as it adds to the typing effort.
 The variable name can be Alpha-numeric e.g. no1
 But it should start with an alphabet.
 It should not contain any spaces in between.
 It should not contain any special symbols except
underscore (_) in between e.g. area_circle
 It should not contain any Keyword.

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C Programming
Keywords:
 The words which are assigned with special meaning to them
in C Compiler are called as keywords. As they are assigned
with special meaning, they can not be used as variable names.
There are only 32 keywords available in C.
auto double int struct
break else long switch
case enum register typedef
char extern return union
const float short unsigned
continue for signed void
default goto sizeof volatile
do if static while

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C Programming
'C' Instructions:
 Type Declaration Instruction: These instructions are used to
declare the type of variables used in a C Program.
 int no1, no2, sum;
 float radius, area;
 char ch;
 Arithmetic Instructions:
 Arithmetic Operators –
Addition + 5 + 2 = 7
Subtraction - 5 – 2 = 3
Multiplication * 5 * 2 = 10
Division / 5 / 2 = 2
Modulus % 5 % 2 = 1
In normal maths, we write instruction as
follows –
A + B = C
In C, we write the same as –
C = A + B
In C '=' is used to assign values to
variables.

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C Programming
 Priority of operators –
 Control Instructions: In C Programming the execution of
program happens from top to bottom. There are certain
instruction in C which can change the flow of the program.
These instructions are called as control instructions. e.g.
while, for, goto etc.
Priority Operators Description
1st ( ) Brackets
2nd * / % Multiplication, Division, Modulus
3rd + - Addition, Subtraction
4th = Assignment

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C Programming
Basic Structure of a C Program:
#include<stdio.h>
#include<conio.h>
void main()
{
……….;
……….;
……….;
}
• # – preprocessor
instruction
• include<x> – To include a
file x to the C Program
• stdio.h / conio.h – Header
Files
• void main() – Start of a
program
• { } – Scope of a Program

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C Programming
Rules for Writing a C Program
 Each Instruction in C Program is written as a separate statement.
 The statements in program must appear in the same order which
we wish them to be executed, unless the logic of the program
demands a deliberate 'jump' or transfer of control to a statement,
which is out of sequence.
 Blank spaces my be inserted between two words to improve the
readability of the statement.
 All syntax should be entered in small case letters.
 Every C statement must end with a ;. Thus ; acts as a statement
terminator.
 There is no specific rule for the position at which the statement is
to be written. That's why it is often called as free-form language.

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C Programming
First C Program
#include<stdio.h>
void main()
{
printf("This is my first C Program"); /*to print the statement*/
}
 The program should be properly documented. The
statements enclosed in /* */ are called as comments.
 Single line comments can also be given using //.
 The program should be properly indented.
 printf() is a function which prints the string embedded in
between " " on the console.

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C Programming
Declaring & Assigning Values to Variables
#include<stdio.h>
#include<conio.h>
void main()
{
int no1;
float no2;
char ch;
no1 = 10;
no2 = 25.75;
ch = 'A';
printf("Integer = %d, Real = %f, Character = %c", no1, no2, ch);
getch(); /*waits for user to press any key on console*/
}
Note: You can assign the
values to the variables at
the time of declaration
also e.g. int no1 = 10;
%d is format specifier for
integers.
%f is format specifier for
real.
%c is format specifier for
character.

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C Programming
scanf() Function
 To receive the values from user scanf() function is used.
 You can receive the single or multiple values within a single scanf.
 e.g. scanf("%d", &no1) or scanf("%d%d“, &no1, &no2);
 Generally before any scanf() statement printf() statement should
be written to guide the user for giving input.
 & means address of the variable.
#include<stdio.h>
void main()
{
int no1;
printf(“nEnter any number: ");
scanf("%d", &no1); /*receives the value from console*/
}

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C Programming
The Decision Control Structure
if statement
 Many times we have to take actions based on certain
conditions. C provides if or if-else statement to allow you to
execute statements based on the conditions.
 Before going into details of conditional statements you must
know the Relational Operators –
less than < x < y
greater than > x > y
less than equal to <= x <= y
greater than equal to >= x >= y
equal to == x == y
not equal to != x != y

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C Programming
Forms of if-else Statements
• if(condition)
……..;
• if(condition)
{
……..;
……..;
}
• if(condition)
……..;
else
……..;
• if(condition)
{
……..;
……..;
}
else
……..;
• if(condition)
……..;
else
{
……..;
……..;
}
• if(condition)
{
……..;
……..;
}
else
{
……..;
……..;
}

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C Programming
Nested if-else Statements
• if(condition)
{
if(condition)
{
……..;
……..;
}
else
{
……..;
……..;
}
}
else
{
if(condition)
{
……..;
……..;
}
else
{
……..;
……..;
}
}

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C Programming
Logical Operators
• C contains Logical
Operators && (AND), ||
(OR) and ! (NOT).
• && and || allow to join
multiple conditions.
• ! Operator reverses the
result of the expression it
operates on.
Examples -
• if(!flag) /*will reverse value of flag*/
{
……..;
……..;
}
• if(cond1 && cond2 && …… && condN)
{
……..;
……..;
}
If all the conditions joined by && are true
then the statements will be executed.
• if(cond1 || cond2 || …… || condN)
{
……..;
……..;
}
If any of the conditions joined by || is true
then the statements will be executed.
• if((cond1 && cond2) || (cond3 && cond4))
{
……..;
……..;
}

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C Programming
The else if Statement
void main()
{
int no1=15, no2=10, no3=8;
if (no1 > no2 && no1 > no3)
printf("The no1 is maximum");
if(no2 > no1 && no2 > no3)
if(no3 > no1 && no3 > no2)
getch();
}
In the above example even if the first
number is maximum the other two if
statements are also checked and this
will increase the execution time of the
program.
void main()
{
int no1=15, no2=10, no3=8;
if (no1 >no2 && no1 > no3)
else if(no2 > no1 && no2 > no3)
else
getch();
}
In the above example if the fist 'if' goes
false then only second if will get
executed and if the second 'if' goes
false then the last else will get
executed.

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C Programming
The Conditional Operators
• The conditional operators ?
and : are sometimes called as
ternary operators since they
take three arguments. Their
general form is –
expression1 ? expression 2 : expression3
The above expression suggests "if
expression1 is true (that is, if it's value
is non-zero), then the value returned
will be expression2, otherwise value
returned will be expression3.
int x, y;
scanf("%d", &x);
y = (x > 5 ? 3 : 4)
This expression will store 3 in y if x is
greater than 5 otherwise it will store 4
in y.
int i;
scanf("%d",&i);
If(i==1 ? printf("Amit") : printf("Rohit);
char a = 'z';
printf("%c", (a >= 'a' ? a : '!'));
int big a, b, c;
big=(a>b ? (a>c ? 3 : 4) : (b>c ? 6 : 8))

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C Programming
The Loop Control Structure
The while loop:
 In programming sometimes you want to run a block of code
repeatedly till certain number of times. The while loop helps
you to achieve this task.
 The general form of while loop is –
initialize the loop counter;
while(test the loop counter using a condition)
{
.........;
………;
increment / decrement loop counter;
}
The loop counter is initialized
before going inside the loop.
If the condition is true, it will
execute all the statements
inside the loop. The counter
will be incremented or
decremented while going
outside the loop. The control
is again passed to while.
This will happen till the
condition is true.

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C Programming
More Operators
++ and -- operators:
• When you want to do increment
by one i.e. if you want to write
i = i + 1, you can use i++ or ++i;
Same way if you want to do
decrement by on i.e. if you want to
write i = i – 1, you can use i--
or --i.
• There is a difference between pre-
increment / post-increment or pre-
decrement / post-decrement
operators. e.g.
int i = 10, j;
j = i++;
printf(" %d %d", i, j); /* 11 10*/
int i = 10, j;
j = ++i;
printf(" %d %d", i, j); /* 11 11*/
In the first example the value of i is
first assigned to j and then the
value of i gets incremented.
In the second example the value of i
is first incremented and then it is
assigned to j.
Compound Assignment Operators
i = i + 5 i+=5 i = i – 5 i-=5
i = i * 5 i*=5 i = i / 5 i/=5
i = i % 5 i%=5

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C Programming
Nesting of while loop
• The way we have seen nesting
of 'if' statements, we can do
nesting of loops. Nesting of
loop means loop into another
loop. Example –
*
**
***
****
• In the above example, you
have to print multiple stars in
columns for each row. Such
times you need nesting of
loops.
void main()
{
int r = 1, c;
while(r <= 4)
{
c = 1;
while (c <= r)
{
printf("*");
c++;
}
printf("n");
r++;
}
getch();
}

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C Programming
do while Loop
• The difference between while and
do while is the do while loop at
least gets executed single time.
initialize the loop counter;
do
{
...........;
………;
increment / decrement loop
counter;
} while (condition);
• do while loop is generally used
with odd loops. When the
programmer does not know how
many time the loop will get
executed the odd loops are used.
#include<stdio.h>
#include<conio.h>
void main()
{
int no1, no2, sum;
char ch;
do
{
printf("Enter 2 nos: ");
scanf("%d%d", &no1, &no2);
sum = no1 + no2;
printf("Sum = %d", sum);
printf("Want to continue <y/n>: ");
flushall();
scanf("%c", &ch);
} while(ch == 'y');
}

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C Programming
for Loop
• for loop specify three things
about the loop in a single line.
• The general form of for
statement is as follows –
for(initialize; condition; increment /
decrement)
{
………..;
………..;
}
e.g.
for(i = 0; i <= 10; i++)
{
printf("%d", i);
}
• In for loop the initializations are
done only at the first time.
Then condition is checked and
while going outside the loop
the loop counter is
incremented or decremented.
• You can do multiple
initializations or multiple
increments / decrements using
comma separation.
e.g.
for(i = 0, j = 5; i < j; i++, j--)
{
printf("%d %d", i, j);
}

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C Programming
break, continue Statement
• break statement is
used to jump out of the
loop instantly.
e.g.
for(i = 0; i <= 10; i++)
{
if(i == 5)
break;
printf("%d ", i);
}
The output of the above program
is:
0 1 2 3 4
• continue statement
takes the control of the
program to the
beginning of loop.
e.g.
for(i = 0; i <= 10; i++)
{
if(i == 5)
continue;
printf("%d ", i);
}
The output of the above program
is:
0 1 2 3 4 6 7 8 9 10

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C Programming
The goto Keyword
• goto keyword allows to
jump the program from one
location to another.
• Though it is easy to use, but
it makes the program
unreliable, unreadable and
hard to debug. So avoid
using it or use it in a very
unavoidable circumstances.
• The word followed by goto
keyword is called as label.
It takes the control to that
specific label.
void main()
{
int i;
for(i = 0; i < 10; i++)
{
if(i == 5)
goto xyz;
else
printf(" %d", i);
}
xyz:
printf("nI am out of main");
}
The output is:
0 1 2 3 4
I am out of main

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C Programming
switch case Control Structure
• The switch-case-default
allows us to make decision
from many choices.
• The expression followed by
switch should be integer or
character.
• The keyword case is followed
by integer or character
constants.
• When user gives some choice
the switch statement takes the
control to the specified case.
• If no such case exists, then
control goes to default.
• Each case ends with break.
• You cannot use logical && or
|| operators with cases.
switch(choice)
{
case 1:
………..;
break;
case 2:
………..;
break;
case 3:
………..;
break;
default:
………..;
}

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C Programming
Functions
• Sometimes there is a code which
occurs repeatedly inside main. To
avoid this repetition we write
functions. Functions helps to
reduce length of code.
• A function is a block of code that
performs a specific assigned task.
• You can call one function from
another function but you cannot
write one function's definition into
another.
• The scope of the variables is
limited to the function.
• Two different functions can have
variables with same name. But
their memory locations are
different.
#include<stdio.h>
void pune();
void mumbai();
void main()
{
printf("nI am in main");
pune();
mumbai();
printf("nI am back in main");
getch();
}
void pune()
{
printf("nI am in Pune");
}
void mumbai()
{
printf("nI am in Mumbai");
}
Call to a
function
Function
Definitions

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C Programming
Functions (Passing Parameters)
#include<stdio.h>
#include<conio.h>
void calsum();
void main()
{
calsum();
getch();
}
void calsum()
{
int no1, no2, add;
printf("nEnter two numbers: ");
add = no1 + no2;
printf("nThe sum is: %d", add);
}
#include<stdio.h>
#include<conio.h>
void calsum(int, int);
void main()
{
int no1, no2;
calsum(no1, no2);
getch();
}
void calsum(int a, int b)
{
int add;
add = a + b;
printf("nThe sum is: %d", add);
}
Actual Arguments
Formal Arguments
In this program we
are parameters to
the function. These
functions are
called as Call by
Value functions.

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C Programming
Functions (Returning Value)
• The function can return a
value to a calling function.
• The function can return only
one value at one call.
• The return statement
immediately passes control to
the calling function.
• Replace void before the
function definition by int, float
or char.
• There can be more than one
return statements in a function
but at a time only one will get
executed.
#include<stdio.h>
#include<conio.h>
int calsum(int, int);
void main()
{
int no1, no2, sum;
sum = calsum(no1, no2);
printf("nThe sum is: %d", sum);
getch();
}
int calsum(int a, int b)
{
int add;
add = a + b;
return add;
}
In this program the
sum function returns
a integer value back
to main. So int is
written instead of
void

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C Programming
Recursive Functions
• You can give a call to a function
from the same function it is called
as recursive function.
#include<stdio.h>
#include<conio.h>
int factorial(int );
void main()
{
int no, fact;
printf("nEnter any number: ");
scanf("%d", &no);
fact = factorial(no);
printf("nThe factorial is: %d",
fact);
getch();
}
int factorial (int no)
{
int f;
if( no == 1)
return(1);
else
f = no * factorial (no – 1);
return(f);
}
• Make sure that the recursive
call is conditional. An
unconditional recursive call will
result to a infinite call.

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C Programming
Recursive Function
from main()
factorial (int no)
{
int f;
if(no == 1)
return(1);
else
f =
no*factorial(no-1);
return(f);
}
to main()
factorial (int no)
{
int f;
if(no == 1)
return(1);
else
f =
no*factorial(no-1);
return(f);
}
factorial (int no)
{
int f;
if(no == 1)
return(1);
else
f =
no*factorial(no-1);
return(f);
}

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C Programming
Data Types Revised
Data Type Range Bytes
Format
Specifiers
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
signed int -32768 to 32767 4 %d
unsigned int 0 to 65535 4 %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 8 %Lf
Note: The sizes in this figure are for 32 bit compiler

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C Programming
C Preprocessor
• There are several steps involved
from the stage of writing a C
Program to the stage of getting it
executed. The combination of
these steps is known as the 'Build
Process'.
• Before the C Program is compiled
it is passed through another
program called as 'Preprocessor'.
• C program is often known as
'Source Code'. The Preprocessor
works on Source Code and creates
'Expanded Source Code'. If
source file is Prog01.C, the
expanded source code is stored in
file Prog01.I. The expanded source
code is sent for compilation.
• The preprocessor directives begin
with # symbol. Generally they are
placed at the start of the program,
before function definitions.
• Following are the preprocessor
directives –
– Macro Expansion
• Simple Macros
• Macros with Arguments
– File Inclusion
– Conditional Compilation
– Miscellaneous Directives

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C Programming
C Preprocessor
Macro Expansion
#define PI 3.142
• The above expression is called as
'macro definition'. During the
preprocessing PI will be replaced
with 3.142.
• PI in above example is called as
'macro template' and 3.142 is
called as 'macro expansion'.
• When we compile the program,
before the source code passes to
the compiler, it is examined by C
preprocessor for macro
definitions. And when it finds the
macro templates they replace it
with appropriate macro expansion.
Some examples -
• #define AND &&
We can use AND instead of &&
• #define OR ||
We can use OR instead of ||
• #define RANGE ( a > 25 && a < 50)
We can use RANGE instead of
(a>25 && a < 50)
• #define FOUND printf("Location
Found");
We can use FOUND instead of
printf("Location Found")

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C Programming
Macros with Arguments
• We can pass arguments to
macros.
#include<stdio.h>
#define AREA(x) (3.142 * x * x)
void main()
{
float r = 5.25, a;
a = AREA(r);
printf("nThe area is : %f", a);
}
When the above code is passed to
preprocessor –
a = AREA(r);
will get converted to –
a = 3.142 * r * r;
Multiline Macros
• Macros can be split into multiple lines
with a '' (back slash) present at the
end of each line.
#include<stdio.h>
#define HLINE for(i=0; i<79; i++)
printf("%c", 196);
#define VLINE(X, Y) {
gotoxy(X, Y);
printf("%c", 179); }
void main()
{
int i, y;
gotoxy(1, 12);
HLINE;
for (y = 1; y < 25; y++)
VLINE(39, y);
}

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C Programming
File Inclusion
• This preprocessor directive
allows us to include one file into
other.
• The large programs can be
divided into different files, each
containing a set of functions.
These files can be included at
the beginning of main program
file.
• The files to be included should
have .h extension. This
extension stands for a 'header
file'.
• Each header file generally
contains related set of functions.
– e.g. math.h will contain all functions
related to mathematics.
• You can include these files into
main using #include
statement.
– #include "filename"
– #include<filename>
• #include "filename" will
search filename into current
directory as well as specified
list of directories mentioned in
the include search path.
• #include <filename> will
search the filename into
specified list of directories
only.

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C Programming
The Build Process
• Preprocessing: The C code is
expanded on preprocessor directives
like #define, #include etc.
• Compilation: If expanded source code
is error free then compiler translates the
expanded source code into equivalent
assembly language program.
• Assembling: The job of Assembler is to
translate .asm code into relocatable
object code. Thus a .asm file gets
converted to .obj file.
• Linking: Linking creates an executable
program. It finds the definitions of all
external functions, finds definitions of all
global variables, combines data sections
into a single data section and combines
code sections into single code section.
And finally .exe file is created.
C Source Code
Prog1.C
Expanded Source
Code Prog1.i
Assembly Code
Prog1.asm
Relocatable
Object Code
Object Code of
Library Functions
Executable Code
Prog1.exe
Linker

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C Programming
Arrays
• Array is a collection of variables of
same data type.
• E.g. if we want to store roll
numbers of 100 students, then
you have to define 100 variables
and which is very difficult to
manage. Instead you can define
one array which can hold 100
variables.
• Declare Array:
int arr[5];
int arr[5] = {10,20,30,40,50};
int arr[ ] = {10,20,30,40,50};
• When you declare an array a
consecutive memory allocation is
done for 5 integers.
• You can initialize the array only at
the time of declaration.
• Array index always starts from
zero.
• If you want to refer array elements
you can use arr[0], arr[1], arr[2]
etc.
• In the following array 10 is a value
at array index 0 having address
6231.
• Memory Map of Array:
10 20 30 40 50
0 1 2 3 4
6231 6235 6239 6243 6247
arr

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C Programming
Arrays
Accept and Print Array:
#include<stdio.h>
#include<conio.h>
void main()
{
int arr[5], i;
printf("nEnter five numbers: ");
for(i = 0; i < 5; i++)
scanf("%d", &arr[i]);
printf("nYou have entered: ");
for(i = 0; i < 5; i++)
printf(" %d", arr[i]);
getch();
}
• As array holds multiple
locations you have to use for
loop while accepting and
printing the array.
• You can define an array of
bigger size and accept the
required no. of values from
user. e.g. you can define an
array of arr[100] and use only
10 locations.
• In C Language the bounds
checking for array is not done.
So the programmer has to be
very careful while accepting or
printing the values from array.

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C Programming
Passing Array to a Function
#include<stdio.h>
#include<conio.h>
void display(int [ ], int);
void main()
{
int arr[5], i;
for(i = 0; i < 5; i++)
display(arr, 5);
getch();
}
void display (int a[ ], int s)
{
int i;
for(i = 0; i < s; i++)
printf(" %d", a[i]);
}

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C Programming
Two Dimensional Arrays
• Array can have two or more
dimensions.
• Declare 2D-Array:
int a[2][2];
int a[ ][2] = {10,20,30,40};
int a[ ][2] = {{10,20},{30,40}};
• Memory Map of 2D-Array:
#include<stdio.h>
#include<conio.h>
void main()
{
int arr[3][3], i, j;
printf("nEnter nine numbers: ");
for(i = 0; i < 3; i++)
for(j = 0; j < 3; j++)
scanf("%d", &arr[i][j]);
for(i = 0; i < 3; i++)
for(j = 0; j < 3; j++)
printf(" %d", arr[i][j]);
getch();
}
10 20 30 40
a[0][0] a[0][1] a[1][0] a[1][1]
6231 6235 6239 6243
a

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C Programming
Passing 2D-Array to a Function
#include<stdio.h>
#include<conio.h>
void display(int [ ][3], int, int);
void main()
{
int arr[3][3], i, j;
printf("nEnter nine numbers: ");
for(i = 0; i < 3; i++)
for(j = 0; j < 3; j++)
scanf("%d", &arr[i][j]);
display(arr, 3, 3);
getch();
}
void display (int a[ ][3], int r, int c)
{
int i, j;
for(i = 0; i < r; i++)
for(j = 0; j < c; j++)
printf(" %d", a[i][j]);
}

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C Programming
Strings
• String is a collection of character
variables. Sometimes you need to
store name, address where you
have to store more than one
characters, you need strings.
• Declare String:
char s[50];
char s[ ] = {'P','a','r','a','g','0'};
char s[ ] = "Parag";
• Memory Map of a String:
• '0' character is automatically
appended at the end while
accepting the string.
#include<stdio.h>
#include<conio.h>
void main()
{
char name[50];
int i;
printf("nEnter your name: ");
//scanf("%s", name);
gets(name);
printf("nYour name is: %s", name);
printf("nYour name is: ");
for(i = 0; name[i] != '0'; i++)
printf("%c", name[i]);
getch();
}
P a r a g 0
0 1 2 3 4 5
6231 6232 6233 6234 6235 6236
s

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C Programming
Strings
• %s is special format specifier to
accept the strings. But it cannot
accept string with spaces. So use
gets(string-name) function to
accept string.
• You can print the string using
puts(string-name) function.
• You are not needed to accept the
size of strings as you require in
case of arrays because C
automatically appends the '0'
character at the end of the string.
Hence you know when a '0'
character appears, that is the end
of the string.
Standard Library Functions
Function Use
strlen
Finds the length of the
string
strlwr
Converts string to
lowercase
strupr
Converts string to
uppercase
strcpy
Copies string to another
string
strcat
Appends one string at
the end of another string
strcmp Compares two string
strrev Reverses the string

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C Programming
Passing String to Function
#include<stdio.h>
#include<conio.h>
void display(char [ ]);
void main()
{
int name[50], i;
gets(name);
display(name);
getch();
}
void display (char str[ ])
{
int i;
printf("nYour name is: %s", str);
printf("nYour name is: ");
for(i = 0; str[i] != '0' ; i++)
printf("%c", str[i]);
}
Output:
Enter your name: Rohit
Your name is: Rohit
Your name is: Rohit

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C Programming
Two Dimensional Strings
• Strings also can have 2 or more
dimensions. When you want to
store multiple names, addresses
that time you need 2-D string.
• Declare 2D-String:
char s[2][10];
char s[ ][10] = {"Parag",
"Pooja",
"Sarang"};
• Memory Map of 2D-String:
#include<stdio.h>
#include<conio.h>
void main()
{
char name[3][50];
int i;
printf("nEnter three names: ");
for(i = 0; i < 3; i++)
gets(name[i]);
printf("nThe names are: ");
for(i = 0; i < 3; i++)
puts(name[i]);
getch();
}
P a r a g 0
P o o j a 0
S a r a n g 0
6231
6241
6251

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C Programming
Passing 2D-String to a Function
#include<stdio.h>
#include<conio.h>
void display(char [ ][50], int);
void main()
{
char name[3][50];
int i;
printf("nEnter three names: ");
for(i = 0; i < 3; i++)
gets(name[i]);
display(name, 3);
getch();
}
void display (char n[ ][50], int s)
{
int i;
printf("nThe names are: ");
for(i = 0; i < s; i++)
puts(n[i]);
}

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C Programming
Pointers
• Pointer is a variable which can
store address of another
variable.
– & means address
– * means value at that
address (except declaration)
#include<stdio.h>
void main()
{
int i = 10, *j;
j = &i;
printf("nAddress of i = %u", &i);
printf("nAddress of i = %u", j);
printf("nAddress of j = %u", &j);
printf("nValue of j = %u", j);
printf("nValue of i = %d", i);
printf("nValue of i = %d", *(&i));
printf("nValue of i = %d", *j);
getch();
}
• The output of above program:
i
10
6231
j
6231
5785
Variable name
Variable value
Variable address
Address of i =
6231
Value of i =
10
Address of i= 6231 Value of i =
10
Address of j =
6233
Value of i =
10
Value of j = 6231

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C Programming
Pointers
#include<stdio.h>
void main()
{
int i = 10, *j, **k;
j = &i;
k = &j;
printf("nAddress of i = %u", &i);
printf("nAddress of i = %u", j);
printf("nAddress of i = %u", *k);
printf("nAddress of j = %u", &j);
printf("nAddress of j = %u", k);
printf("nAddress of k = %u", &k);
printf("nValue of j = %u", j);
printf("nValue of k = %u, k);
printf("nValue of i = %d", i);
printf("nValue of i = %d", *(&i));
printf("nValue of i = %d", *j);
printf("nValue of i = %d", **k);
getch();
}
The output of the program:
Address of i = 6231
Address of i = 6231
Address of i = 6231
Address of j = 6233
Address of j = 6233
Address of k =6235
Value of j = 6231
Value of k = 6233
Value of i = 10
Value of i = 10
Value of i = 10
Value of i = 10
i
10
6231
k
5827
8989
j
6231
5827

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C Programming
Call By Reference Functions
• We have already seen the call by
value type of functions. The
disadvantage of call by value is
you can return only one value and
only once.
• To overcome the disadvantage of
call by value we can use call by
reference type of functions.
• When you pass address of a
variable to function that time the
function is called as call by
reference.
• In the below example though we
have not returned the value back
to calling function, we get the
value back to sum variable due to
pointer.
#include<stdio.h>
#include<conio.h>
void calsum(int, int, int *);
void main()
{
int no1, no2, sum;
printf("nEnter two numbers:");
calsum(no1, no2, &sum);
printf("nSum = %d");
getch( );
}
void calsum(int x, int y, int *add)
{
*add = x + y;
}

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C Programming
Passing Array to Function using Pointers
• When we want to pass the array
to function using pointers we pass
it as display(arr, size) and catch
it in function using void
display(int *b, int s).
• So if arr is as follows –
So the base address of arr will
be stored in b. So b will hold
6231.
• When you do pointer++ it will be
increased by no. of bytes of it's
datatype.
#include<stdio.h>
void display (int *, int);
void main()
{
int arr[5], i;
for(i = 0; i < 5; i++)
display(arr, 5);
getch();
}
void display (int *b, int s)
{
int i;
for(i = 0; i < s; i++)
printf(" %d", *(b+i));
}
10 20 30 40 50
0 1 2 3 4
6231 6235 6239 6243 6247
arr

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C Programming
Passing String to Function using Pointers
• When we want to pass the string
to function using pointers we pass
it as display(str) and catch it in
function using
void display(char *s).
• So if string is as follows –
So the base address of str will
be stored in s. So s will hold
6231.
• There is no need to pass size of
the string as the end character of
string holds '0';
#include<stdio.h>
#include<conio.h>
void display (char *);
void main()
{
char str[50];
gets(str);
display(str);
getch();
}
void display (char *s)
{
printf("nYou have entered: %s", s);
for( ; *s != '0'; s++)
printf("%c", *s);
}
P a r a g 0
0 1 2 3 4 5
6231 6232 6233 6234 6235 6236
str

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C Programming
Structures
• If we see real world data it is a
combination of integers,
characters, floats, arrays,
strings etc. So we can call it as
a heterogeneous data.
• If we want to store data of a
student then we need to store
her/ his Roll Number, Name,
Address, Age, Gender, Phone
No., E-mail etc. So to store this
kind of data we can use
structures.
• Structure is also called as
User Defined Datatype.
struct stud
{
int roll_no;
char name[20];
char gender;
};
• Above syntax is used to define
a structure.
• Memory Map of Structure:
1 Parag Patki 50stud
roll_no name gender
6231 6235 6255

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C Programming
Structures
#include<stdio.h>
#include<conio.h>
struct stud
{
int roll_no;
char name[50], address[100];
char gender;
};
void main()
{
struct stud s;
printf("nEnter roll number:");
scanf("%d", &s.roll_no);
printf("nEnter name: ");
flushall( );
gets(s.name);
printf("nEnter address: ");
flushall();
gets(s.address);
printf("nEnter gender <y/n>: ");
flushall( );
scanf("%c", &s.gender);
printf("nRoll No. is: %d", s.roll_no);
printf("nName is: %s", s.name);
printf("nAddress is: %s", s.address);
printf("nGender is: %c", s.gender);
getch();
}

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C Programming
Nested Structures
#include<stdio.h>
#include<conio.h>
struct p_details
{
int roll_no;
char name[50];
char gender;
char email[50];
};
struct e_student
{
int m1, m2;
struct p_details p;
};
void main()
{
struct e_student e;
printf("nEnter roll number:");
scanf("%d", &e.p.roll_no);
printf("nEnter Name: ");
flushall( );
gets(e.p.name);
printf("nEnter Gender <y/n>: ");
flushall( );
scanf("%c", &e.p.gender);
printf("nEnter E-mail: ");
flushall( );
gets(e.p.email);
printf("Enter marks of three subjects:");
scanf("%d%d", &e.m1, &e.m2);
printf("nName = %s", e.p.name);
printf("nRoll No. = %d", e.p.roll_no);
printf("nGender = %c", e.p.gender);
printf("nEmail = %s", e.p.email);
printf("Marks = %d %d", e.m1, 2.m2);
getch( );
}

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C Programming
Array of Structures
#include<stdio.h>
#include<conio.h>
struct student
{
int roll_no;
char name[50];
int m1, m2;
};
typedef struct student STUD;
void main()
{
STUD s[50];
int i, size;
printf("nEnter no. of records: ");
scanf("%d", &size);
printf("nEnter %d records:", size);
for(i=0; i<size; i++)
{
printf("nEnter roll no.:");
scanf("%d", &s[i].roll_no);
flushall( );
gets(s[i].name);
printf("nEnter marks:");
scanf("%d%d", &s[i].m1, s[i].m2);
}
printf("nnnRecords are:");
for(i=0; i<size; i++)
{
printf("nRoll no.: %d", s[i].roll_no);
printf("nName: %s", s[i].name);
printf("nMarks:%d %d", s[i].m1, s[i].m2);
}
getch( );
}

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C Programming
Passing Structure to Function
#include<stdio.h>
#include<conio.h>
typedef struct stud
{
int roll_no;
char name[50];
int m1, m2;
}STUD;
void display(STUD);
void main( )
{
STUD s;
printf("nEnter Roll Number: ");
flushall( );
gets(s.name);
printf("nEnter Marks:");
scanf("%d%d", &s.m1, &s.m2);
display(s);
getch( );
}
void display(STUD s1)
{
printf("nRoll No.: %d", s1.roll_no);
printf("nName: %s", s1.name);
printf("nMarks: %d %d", s1.m1, s1.m2);
}

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C Programming
Passing Array of Structures to Function
#include<stdio.h>
#include<conio.h>
struct stud
{
int roll_no;
char name[50];
int m1, m2;
};
void display(struct stud[ ] );
void main( )
{
int I;
struct stud s[5];
for(i=0;i<5;i++)
{
flushall( );
gets(s[i].name);
scanf("%d%d", &s[i].m1, &s[i].m2);
}
display(s);
getch( );
}
void display(struct stud s1[ ])
{
for(int i=0;i<5;i++)
{
printf("nRoll No.: %d", s1[i].roll_no);
printf("nName: %s", s1[i].name);
printf("nMarks: %d %d", s1[i].m1, s1[i].m2);
}
}

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C Programming
Structure to Pointer
#include<stdio.h>
#include<conio.h>
struct stud
{
int roll_no;
char name[50];
int m1, m2;
};
void display(struct stud *);
void main( )
{
struct stud s;
flushall( );
gets(s.name);
scanf("%d%d", &s.m1, &s.m2);
display(&s);
getch( );
}
void display(struct stud *s1)
{
printf("nRoll No.: %d", s1->roll_no);
printf("nName: %s", s1->name);
printf("nMarks: %d %d", s1->m1, s1->m2);
}

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C Programming
Passing Array of Structures to Pointer
#include<stdio.h>
#include<conio.h>
struct stud
{
int roll_no;
char name[50];
};
void display(struct stud *, int);
void main()
{
struct stud s[3];
int i;
printf("nEnter 3 records: nn");
for(i=0; i<3; i++)
{
printf("nEnter roll no.: ");
flushall();
gets(s[i].name);
printf("nn");
}
display(s,3);
getch();
}
void display(struct stud *s1, int n)
{
int i;
printf("nYou have entered: nn");
for(i=0; i<n; i++, s1++)
{
printf("nEnter roll no.: %d", s1->roll_no);
printf("nEnter Name: %s", s1->name);
}
}

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C Programming
Input / Output in C
• There are two types of I/O.
– Console I/O
– File I/O
• Till now whatever programs we
have seen, in those programs
data vanishes when the
program ends. So to store the
data on the disk we need file
I/O operations.
• All the data on the disk is
stored in binary form. But the
process of storing data varies
from OS to OS. The
programmer uses library
function in a particular OS to
perform I/O.
• There are different operations
that can be carried out on the
file:
– Creation of new file
– Opening an existing file
– Reading from a file
– Writing to a file
– Moving to a specific location in
the file
– Closing a file

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C Programming
Display Contents of File on Console
#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
void main( )
{
FILE *fp;
char ch;
fp = fopen("Source.txt", "r");
if(fp == NULL)
{
puts("Cannot open source file");
exit(1);
}
while(1)
{
ch = fgetc(fp);
if(ch == EOF)
break;
printf("%c", ch);
}
fclose(fp);
getch();
}
• FILE is a inbuilt structure defined in
stdio.h header file.
• fopen() function searches the file on
disk to be opened, if file found it loads
it into buffer and it sets up a character
pointer that points to the first
character of buffer. If file not found it
returns NULL.
• exit() function terminates the
program.
• while(1) is a infinite loop.
• fgetc(fp) function returns the
character present at the pointer fp
and moves the pointer to the next
location.
• EOF stands for End Of File
character which indicates the end of
file.
• fclose() function closes the file.

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C Programming
Writing From One File to Another
#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
void main( )
{
FILE *fs, *ft;
char ch;
fs = fopen("Source.txt", "r");
if(fs == NULL)
{
exit(1);
}
ft = fopen("Target.txt", "w");
if(ft == NULL)
{
puts("Cannot open target file");
fclose(fs);
exit(2);
}
while(1)
{
ch = fgetc(fs);
if(ch == EOF)
break;
else
fputc(ch, ft);
}
fclose(fs);
fclose(ft);
printf("File copied successfully");
getch();
}
• fputc(ch, ft) writes the character ch to
the file location ft and moves pointer
ahead to next location.

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C Programming
Writing String Received From Keyboard to File
#include<stdio.h>
#include<conio.h>
#include<string.h>
#include<stdlib.h>
void main( )
{
FILE *fp;
char s[80];
fp = fopen("Target.txt", "w");
if(fp == NULL)
{
puts("Cannot open file");
exit(1);
}
printf("nEnter few lines: ");
while(strlen(gets(s)) > 0)
{
fputs(s, fp);
fputs("n", fp);
}
fclose(fp);
printf("Data writing successful");
getch();
}
• The function fputs() writes the
given string to the file. Since
fputs() does not add newline
character automatically we have
to add it explicitly.

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C Programming
Reading String From File and Printing on Console
#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
void main( )
{
FILE *fp;
char s[80];
fp = fopen("Target.txt", "r");
if(fp == NULL)
{
exit(1);
}
printf("nThe file data is:n");
while(fgets (s, 79, fp) != NULL)
printf("%s", s);
fclose(fp);
getch();
}
• The function fgets() requires
three arguments. The first is
the address where the string
is stored, the second is
maximum length of string
and the third argument is the
pointer to the structure FILE.
When all the lines from the file
have been read, fgets() returns
NULL.

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C Programming
Write Records to File Using Structure
#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
void main( )
{
FILE *fp;
char ch;
struct emp
{
char name[50];
int age;
float sal;
};
struct emp e;
fp = fopen("Data.txt", "w");
if(fp == NULL)
{
exit(1);
}
do
{
printf("nEnter name, age, sal:");
scanf("%s%d%f", e.name, &e.age, &e.sal);
fprintf(fp, "%s %d %fn", e.name, e.age,
e.sal);
printf("nAdd another record <y/n>: ");
fflush(stdin);
ch = getche();
}while(ch == 'y');
fclose(fp);
printf("nData written successfully:");
getch();
}
• fprintf() writes the structure to file. The first
argument is FILE pointer,

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C Programming
Read Records From File Using Structure
#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
void main( )
{
FILE *fp;
char ch;
struct emp
{
char name[50];
int age;
float sal;
};
struct emp e;
fp = fopen("Data.txt", "r");
if(fp == NULL)
{
exit(1);
}
while(fscanf (fp, "%s %d %f",
e.name, &e.age, &e.sal) != EOF)
printf("n%s %d %f", e.name,
e.age, e.sal);
fclose(fp);
getch();
}

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C Programming
Writing Records Using fwrite()
#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
void main( )
{
FILE *fs;
char another;
struct emp
{
char name[50];
int age;
float sal;
}e;
fs = fopen("Source.txt", "wb");
if(fs == NULL)
{
exit(1);
}
do
{
printf("nEnter name, age, sal:");
scanf("%s%d%f", e.name, &e.age, &e.sal);
fwrite(&e, sizeof(e), 1, fs);
printf("nAdd another record <y/n>?: ");
fflush(stdin);
another = getche();
}while(another == 'y');
fclose(fs);
printf("nData written successfully to file");
getch();
}
• In fwrite() function the first argument is the
address of the structure, the second argument
is size of structure in bytes, the third argument
is the number of elements to be written and the
last argument is the pointer to file where we
want to write to.

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C Programming
Reading Records Using fread()
#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
struct emp
{
char name[50];
int age;
float sal;
}e;
void main( )
{
FILE *fs;
fs = fopen("Source.txt", "rb");
if(fs == NULL)
{
exit(1);
}
while(fread (&e, sizeof(e), 1, fs) == 1)
printf("n%s %d %f", e.name,
e.age, e.sal);
fclose(fs);
}

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C Programming
• In C it is possible to accept command
line arguments. Command-line
arguments are given after the name of
a program in command-line operating
systems and are passed in to the
program from the operating system.
To use command line arguments in a
program, we first see the full
declaration of the main function, which
previously has accepted no
arguments.
void main(int argc, char *argv[])
• The integer, argc is the ARGument
Count. It is the number of arguments
passed into the program from the
command line, including the name of
the program.
• The character pointer, *argv[] is the
ARGument Values list. It has
elements specified in the previous
argument, argc.
Command Line Arguments

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C Programming
Command Line Arguments
#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
void main( int argc, char *argv[])
{
FILE *fs, *ft;
char ch;
if(argc != 3)
{
puts("Improper no. of arguments");
getch();
exit(1);
}
fs = fopen(argv[1], "r");
if(fs == NULL)
{
getch();
exit(2);
}
ft = fopen(argv[2], "w");
if(ft == NULL)
{
puts("Cannot open target file");
fclose(fs);
getch();
exit(2);
}
while(!feof(fs))
{
ch = fgetc(fs);
fputc(ch, ft);
}
fclose(fs);
fclose(ft);
printf("File copied successfully");
getch();
}

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C Programming
Debugging an “argc-argv” Program
Step 1

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C Programming
Step 2

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Step 3

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C Programming
 Execute the program and check the output.
 The arguments will be taken as given by you.
 NOTE: You can give strings as arguments within “ “.
 Make sure that: hi how are you, has 4 arguments whereas: hi
“how are” you has just 3.
Continued..

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C Programming
END OF BASICS IN C
 Thus, the basics of C programming ends here.
 We hope you are satisfied with the theory provided.
 Feel free to share, distribute or use it in any form you wish to.
IT IS FOR YOU. 

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C Programming
For advance C programming course or for any doubts in this
tutorial, please contact us on any of the following details:
Call us on: 02065000419 / 02065111419
E-mail us at: prog@ecti.co.in
Web URL: www.ecti.co.in
For any suggestions of complaints regarding the theory or
programs in the tutorial, write us at:
complaints@ecti.co.in
END OF BASICS IN C

C programming

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