Udayakumar C/Asst. Prof./B.Sc CS(AI&DS)/M.G.

R ollege/Hosur/2024

UNIT-II
Decision Making , Looping and Arrays-Decision Making and Branching:
Introduction – if, if….else, nesting of if …else statementselse if ladder –
The switch statement, The ?: Operator – The go to Statement. Decision
Making and Looping: Introduction- The while statement- the do
statement – the for statement-jumps in loops. Arrays – Character Arrays
and Strings
Introduction
 Control structures are used to transfer control form one statement in
a program to any other statement
The control statements are classified as follows

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Decision Making Statements

 Decision making is about deciding the order of execution of

statements based on certain conditions or repeat a group of
statements until certain specified conditions are met
Decision Making with if Statement

 The if statement may be implemented in different forms depending on

the complexity of conditions to be tested

Simple if Statement
 C uses the keyword if to execute a set of statements when logical
condition is true

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 When the logical condition is false, the compiler simply skips

the statement within the block
 The "if" statement is also known as one way decision statement

Syntax:
if(condition)
{
//Statement to be executed
//if condition is true
Statement 1;
Statement 2;
. .
. .

Statement n;
}
Flow diagram

 Here ‘Block of statement‘will wok if and only if the condition is true.

 ‘Statement 2‘ will work even the condition is true or false
Example
#include <stdio.h>
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int main()
{
int x = 15;
if (x > 20)
{
printf("15 is greater than 20");
}
printf("The statement executed is outside the if block");
}
Output
The statement executed is outside the if block
The if...else Statement

 C uses the keywords if and else to execute a set of statements

either logical condition is true or false
 If the condition is true, the statements under the keyword if
will be executed
 If the condition is false, the statements under the keyword else
will be executed

Syntax
if(condition)
{
//Execute this block
//if condition is true
}
else

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{
//Execute this block
//if condition is false
}
Flow diagram

Example Program
#include <stdio.h>
int main(void)
{
int n;
printf("\n Enter the number : ");
scanf("%d", &n);
if(n%2 == 0)
printf("\n %d is even", n);
else
printf("\n %d is odd", n);
return 0;
}

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Output:
Enter the number : 4
4 is even
Nested if...else Statement

Syntax
if(Test Expression 1)
{
if(Test Expression 2)
{
statement block 1;
}
else
{
statement block 2;
}
}
else
{
if(Test Expression 3)
{
statement block 3;
}
else
{
statement block 4;
}
}

The nested if...else statement works as follows:

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 First, Test Expression 1 is checked, if it is true, then the Test Expression

2 is checked, if it is true then statement block 1 is executed. Otherwise,
statement block 2 is executed
 Otherwise, if the Test Expression 1 is false, then Test Expression 3 is
checked, if it is true then statement block 3 is executed. Otherwise,
statement block 4 is executed
Flow diagram

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Example Program

#include <stdio.h>
int main(void)
{
int a, b, c;
printf("Enter three numbers : ");
scanf("%d%d%d \n",&a, &b, &c);
if(a > b)
{
if(a > c)
{
printf("a is the greatest");
}
else
{
printf("c is the greatest");
}
}
else
{
if(b > c)
{
printf("b is the greatest");
}
else
{
printf("c is the greatest");
}

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}
return 0;
}
Output
Enter three numbers : 12 9 11
a is the greatest
The if-else-if statement
 If else ladder is used, If we want to check for multiple conditions one
after another
Syntax
if(Test Expression 1)
{
statement block 1;
}
else if(Test Expression 2)
{
statement block 2;
}
...........................
else
{
statement block x;
}
statement y;

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Flow Diagram

Example Program
#include <stdio.h>
int main(void)
{
int num;
printf("\n Enter any number : ");
scanf("%d", &num);
if(num==0)
printf("\n The value is equal to zero");
else if(num > 0)
printf("\n The number is positive");
else
printf("\n The number is negative");
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return 0;
}
Output
Enter any number : 12
The number is positive
Switch Case
 The switch case statement is used when we have multiple options and
we need to perform a different task for each option
 A switch statement is an alternative to if-else-if statement
The switch statement has four important elements.
 The test expression
 The case statements
 The break statements
 The default statement
Syntax
switch (expression)
{
case value1:
// statement sequence
break;
case value2:
// statement sequence
break;
.
.
.

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case valueN:
// statement sequence
break;
default:
// default statement sequence
}
Flow Diagram

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Example Program
#include <stdio.h>
int main()
{
int i=2;
switch (i)
{
case 1:
printf("Case1 ");
break;
case 2:
printf("Case2 ");
break;
case 3:
printf("Case3 ");
break;
case 4:
printf("Case4 ");
break;
default:
printf("Default ");
}
return 0;
}
Output
Case 2

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Looping Statements

while Loop

 The while loop in C is used to evaluate a test condition and iterate over
the loop body until the condition returns True

 The loop ends when the condition returns False

 This loop is also known as a pre-tested loop

 It is commonly used when the number of iterations is unknown to the

user ahead of time.

Syntax
while (condition)
{
// Code to execute as long as the condition is true
}
Here,
while: This is the keyword that begins the while loop
condition: This is a Boolean expression
The code inside the curly braces {} is the body of the loop
Flow diagram

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Example
#include<stdio.h>
int main()
{
int number=10;

while(number <= 20)

{
printf("%d ", number);
number = number + 1;
}
return 0;
}
Output
10 11 12 13 14 15 16 17 18 19 20
do…while Loop in C
 The do…while in C is a loop statement used to repeat some part of the
code till the given condition is fulfilled
 It is a form of an exit-controlled or post-tested loop
 The test condition is checked after executing the body of the loop
 The statements in the do…while loop will always be executed at least
once
Syntax
do
{
// body of do-while loop

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} while (condition);
Flow diagram

Example
#include <stdio.h>
int main()
{
// loop variable declaration and initialization
int i = 0;
// do while loop
do {
printf("Skill Vertex\n");
i++;
} while (i < 3);
return 0;
}
Output
Skill Vertex
Skill Vertex
Skill Vertex

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For loop
 This is one of the most frequently used loop in C programming
 For loop is a loop in which all three statements initialization,
condition and increment/decrement is given in a single step (before
the code)
 Code may be executed for 0 or more times
 A loop is used for executing a block of statements repeatedly until a
given condition returns false
 It is good if number of iteration(repetition) is known by the user
Syntax
for ( starting value; condition; incrementation or
decrementation )
{
statements;
}

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Flow diagram

Example
#includ<stdio.h>
int main()
{
int i;
for (i=1; i<=3; i++)
{
printf("%d\n", i);
}
return 0;
}
Output
1
2
3
Jump Statements

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 Jump statements in C are used to alter the normal sequence of

execution of a program
 They allow the program to transfer control to a different part of the
code
Types of Jump Statements in C
 break
 continue
 goto
 return
Break
 “break” is a keyword in C used to terminate a block of code that
controls the flow of the program such as switch-case and loops
Syntax

Flow diagram

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Example
#include <stdio.h>
int main()
{
int num =0;
while(num<=100)
{
printf("value of variable num is: %d\n", num);
if (num==2)
{
break;
}
num++;
}
printf("Out of while-loop");
return 0;
}
Output
value of variable num is: 0
value of variable num is: 1
value of variable num is: 2
Out of while-loop
Continue
 The “continue” keyword is used to skip an iteration of the loop if a
certain condition is met
 It is used inside loop along with the decision-making statements

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 When continue statement encounters, the execution will go to the

starting of the loop
 The statements below continue statement will not be executed, if the
given condition becomes true
Syntax
continue;
Pictorial Explanation

Flow Diagram

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Example
#include<stdio.h>

int main()
{
int i;

for(i=1;i<=100;i++)
{
if(i == 25 || i == 50 || i == 75)
continue;

printf("%d\n",i);
}

return 0;
}
Output
It will print numbers from 1 to 100 except the numbers 25,50 and 75

goto
 C programming introduces a goto statement by which you can jump
directly to a line of code within the same file
 The programmer needs to specify a label or identifier with the goto
statement

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Syntax

Flow Diagram

Example
#include<stdio.h>
int main ()

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{ /* local variable definition */ int a = 10;

/* do loop execution */
LOOP:
do
{
if( a == 15) { /* skip the iteration */
a = a + 1;
goto LOOP;
}
printf("value of a: %d\n", a);
a++; }while( a < 20 );
return 0;
}
Output
value of a: 10
value of a: 11
value of a: 12
value of a: 13
value of a: 14
value of a: 16
value of a: 17
value of a: 18
value of a: 19
Return
 The return statement terminates the execution of a function and
returns control to the calling function

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 Every function should have a return statement as its last statement

 The default return type is int
Syntax

Example

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Arrays
 C Programming Arrays is collection of the Elements of the same data
type
 All Elements are stored in the Contiguous memory
 All elements in the array are accessed using the subscript variable
(index)
 C programming structure to store fixed-size, multiple values

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 It is used to hold a collection of primitive data, such as float, char,

int, etc

Array Terminologies
Size:
 Number of elements or capacity to store elements in an array
 It is always mentioned in square brackets [ ]
Type:
 Refers to data type
 It decides which type of element is stored in the array
Base:
 The address of the first element is a base address
 The array name itself stores address of the first element
Index:
 The array name is used to refer to the array element. For example
num[x], num is array and x is index
 The value of x begins from 0
 The index value is always an integer value

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Range:
 Value of index of an array varies from lower bound to upper bound
For example in num[100] the range of index is 0 to 99
Word:
 It indicates the space required for an element
 In each memory location, computer can store a data piece
 The space occupation varies from machine to machine
 If the size of element is more than word (one byte) then it occupies
two successive memory locations
 The variables of data type int, float, long need more than one byte in
memory
One-dimensional Arrays
 The one-dimensional arrays in C language have just one dimension
 They are represented by a single row or column
Syntax
data_type array_name [size];
Array declaration

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Example
#include<stdio.h>
int main() {
// Declare an array of integers
int numbers[5];
// Initialize the array elements
numbers[0] = 10;
numbers[1] = 20;
numbers[2] = 30;
numbers[3] = 40;
numbers[4] = 50;
// Access and print array elements
printf("Array elements: ");
for (int i = 0; i < 5; i++) {
printf("%d ", numbers[i]);
}
printf("\n");
return 0;
}
Output
Array elements: 10 20 30 40 50
Initialize an Array
 Initializing an array means assigning an initial value to the variable
After array declaration
Syntax
data_type array_name [size] = {value1, value2, ... valueN};

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Access Array Elements

 Access an element by indexing the array name
 The array subscript operator [ ] to place the index after the array
name
 Index will start from ‘0’ to ‘array_size-1”. This is known as zero-
based indexing
Syntax
Array_name [index];

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Example
Initializing and Accessing Array Elements
#include<stdio.h>
int main() {
// Declare and initialize an array
int numbers[] = {10, 20, 30, 40, 50};
// Access and print array elements
printf("Array elements: ");
printf("%d ", numbers[0]); // Accessing the first element
printf("%d ", numbers[1]); // Accessing the second element
printf("%d ", numbers[2]); // Accessing the third element
printf("%d ", numbers[3]); // Accessing the fourth element
printf("%d ", numbers[4]); // Accessing the fifth element
printf("\n");
return 0;
}
Output
Array elements: 10 20 30 40 50
Example Program
#include<stdio.h>
#include<conio.h>
void main()
{
int a[10],i,j,t,n;
clrscr();
scanf("%d",&n);

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for(i=0;i<n;i++)
scanf("%d",&a[i]);
for(i=0;i<n-1;i++)
{
for(j=i+1;j<n;j++)
{
if(a[i]>a[j])
{
t=a[i];
a[i]=a[j];
a[j]=t;
}
}
}
for(i=0;i<n;i++)
printf("%d\n",a[i]);
getch();
}
Input
8
5
3
6
1
Output
1

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3
5
6
8
Multi-dimensional Arrays in C
 They have more than one dimension, such as 2-D and 3-D arrays
 Two dimensional arrays will be in the form of rows and columns
format
Syntax of 2-D Array
datatype array_name[size1] [size2];
Example
#include<stdio.h>
int main()
{
int i, j;
int a[3][2] = { { 1, 4 },{ 5, 2 },{ 6, 5 }};
for (i = 0; i < 3; i++)
{
for (j = 0; j < 2; j++)
{
printf("%d ", a[i][j]);
}
printf("\n");
}
return 0;
}

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Output
14
52
65
Example
#include<stdio.h>
int main()
{
int i, j;
int a[3][2] = { { 1 },{ 5, 2 },{ 6 }};
for (i = 0; i < 3; i++)
{
for (j = 0; j < 2; j++)
{
printf("%d ", a[i][j]);
}
printf("\n");
}
return 0;
}
Output
10
52
60
Example
#include<stdio.h>

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int main()
{
int rowCount, columnCount, i, j;
int firstMatrix[10][10], secondMatrix[10][10],
resultMatrix[10][10];

printf("Number of rows of matrices to be added : ");

scanf("%d", &rowCount);

printf("Number of columns matrices to be added : ");

scanf("%d", &columnCount);

printf("Elements of first matrix : \n");

for (i = 0; i < rowCount; i++)

for (j = 0; j < columnCount; j++)
scanf("%d", &firstMatrix[i][j]);

printf("Elements of second matrix : \n");

for (i = 0; i < rowCount; i++)

for (j = 0; j < columnCount; j++)
scanf("%d", &secondMatrix[i][j]);

printf("Sum of entered matrices : \n");

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for (i = 0; i < rowCount; i++)

{
for (j = 0; j < columnCount; j++)
{
resultMatrix[i][j] = firstMatrix[i][j] + secondMatrix[i][j];
printf("%d\t",resultMatrix[i][j]);
}
printf("\n");
}
return 0;
}
Output
Number of rows of matrices to be added : 2
Number of columns matrices to be added : 2
Elements of first matrix :
5
5
5
5
Elements of second matrix :
1
1
1
1
Difference of entered matrices :
6 6

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6 6
Character Arrays
 Character arrays to store strings and then we can apply multiple
operations on strings like modifying a string, copying a string,
concatenation of a string to another, finding properties of strings like
length of the string etc.
 The character array should be large enough to accommodate the
string. i.e. If we have a string “Rahul” then to store the string we need
a character array of size 6
Syntax
storageclass chardatatype arrayname[exp];
Example
char name[50];
Initializing the Character Array
 Each element of the array is placed in a definite memory space and
each element can be accessed separately
 The array element should end with the null character as a reference
for the termination of the character array
 The computer will treat them as a single character
char name[5]="Rahul";
The elements would be assigned to each of the character array
position in the following way
name[0]='R'; name[1]='a'; name[2]='h'; name[3]='u'; name[4]='l';
Character Array in the Memory

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Example
#include <stdio.h>
int main() {
// Character array example
char charArray[6] = {'H', 'e', 'l', 'l', 'o', '\0'};
printf("Character Array: %s\n", charArray);
Output
Character Array: Hello

Example
#include <stdio.h>
#include <conio.h>
#define NUM_ITEMS 5 //optional
main()
{
charstr[12];
str[0]='H'; str[1]='e'; str[2]='l'; str[3]='l'; str[4]='o';
str[5]=' '; str[6]='W'; str[7]='o'; str[8]='r'; str[9]='l';
str[10]='d'; str[11]='\0';

printf( "Your string is: %s", str );

getch();
}
Output
Your string is: Hello World

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The above building up the string by setting each character in

the array, so that the entire array looks something like the table below

str[number] 0 1 2 3 4 5 6 7 8 9 10 11
Contents H E l l o W o r l d \0
ASCII code 72 101 108 108 111 32 87 111 114 108 100 0

Strings
 Sequence of characters enclosed in double quotes is called a string
 A character array is also called as a string
 Every string ends with a null character '\0'
Example
“string_constant”
Declaring String
A string variable should be declared as a character type array and is
used to store string
Syntax
datatype variablename [size];
Example
char city[10];

String Handling Functions

 These are used to carry out string manipulations
 String handling functions are available in the header file string.h
The functions are given below
1.strlen()-Counting the length of a string
2.strcat()-Joining two strings
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3.strcmp() -Comparing two strings

4.strrev()-Reversing string
5.strupr()-Converting lower case string to upper case
6.strlwr()- Converting upper case string to lower case
7.strcpy()-Copying one string to another
Strlen()
 strlen() function is used to find out the length of the given string
 It takes the string as a parameter and returns the integer value

Syntax
strlen(str);
Example
strlen("computer");

Example
#include.stdio.h>
main()
{
char s[100];
static int len;
clrscr();
printf("\nEnter the string:");
gets(s);
len=strlen(s);
printf("\nlength=%d",len);
getch();
}
Output

Enter the string:computer

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Udayakumar C/Asst. Prof./B.Sc CS(AI&DS)/M.G.R ollege/Hosur/2024

length=8

strcat()

 strcat() function is used to combine two given strings. It takes two

string parameters
Syntax
strcat(str1,str2);
Example
strcat("computer","science");

Example
#include.stdio.h>
main()
{
char s[100],c[100];
clrscr();
printf("\nEnter first string:");
gets(s);
printf("\nEnter second string:");

Fundamentals of Computer Programming/2023 Regulations

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Udayakumar C/Asst. Prof./B.Sc CS(AI&DS)/M.G.R ollege/Hosur/2024

gets(c);
printf("\nAfter concatenation: %s",strcat(s,c));
getch();
}
Input
Enter first string:computer

Enter second string:science

Output
After concatenation: computerscience
strcmp()

 strcmp() function is used to compare two given strings

 It takes two string parameters
 The strcmp() returns 0 if two strings are alphabetically equal two
strings are alphabetically equal
 The strcmp() returns +ve value if first string is alphabetically greater
than the second string
 The strcmp() returns the -ve value if first string is alphabetically less
than the second string
Syntax
strcmp(str1,str2);
Example
strcmp("aeri","aeri");

Example
#include.stdio.h>
main()
{
char s[100],c[100];

Fundamentals of Computer Programming/2023 Regulations

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Udayakumar C/Asst. Prof./B.Sc CS(AI&DS)/M.G.R ollege/Hosur/2024

clrscr();
printf("\nEnter first string:");
gets(s);
printf("\nEnter second string:");
gets(c);
if(strcmp(s,c)==0)
printf("strings are equal");
else if(strcmp(s,c)>0)
printf("\n first string is biggerthan second");
else
printf("\nsecond string is biggerthan first");
getch();
}
Input
Enter first string:HOSUR
Enter second string:HOSUR
output
strings are equal
strrev()
 strrev() function is used to reverse the given string
 It takes the string as the parameter
Syntax
strrev(str);
Example
strrev("aeri");

Example
#include<stdio.h>
main()
{

Fundamentals of Computer Programming/2023 Regulations

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Udayakumar C/Asst. Prof./B.Sc CS(AI&DS)/M.G.R ollege/Hosur/2024

char s[100];
clrscr();
printf("\nEnter the string:");
gets(s);
printf("\nreverse string is=%s",strrev(s));
getch();
}
Input
Enter the string:aeri
Output
reverse string is=irea

strupr()
 strupr() function is used to convert the given string into uppercase
 It takes the string as parameter
Syntax
strupr(str);
Example
strupr("aeri");

Example
#include<stdio.h>
main()
{
char s[100];
clrscr();
printf("\nEnter string:");
gets(s);
printf("\nstring in uppercase:%s",strupr(s));
getch();

Fundamentals of Computer Programming/2023 Regulations

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Udayakumar C/Asst. Prof./B.Sc CS(AI&DS)/M.G.R ollege/Hosur/2024

}
Input
Enter string:aeri
Output

string in uppercase:AERI
strlwr()
 strlwr() function is used to convert the given string into lowrcase
 It takes the string as parameter

Syntax
strlwr(str);
Example
strlwr("aeri");

Example
#include<stdio.h>
main()
{
char s[100];
clrscr();
printf("/nEnter string:");
gets(s);
printf("/nstring in lowercase:%s",strlwr(s));
getch();
}
Input
Enter string:AERI
Output
string in lowercase:aeri

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