Unit 6. Arrays

Arrays
• An array is used to store a collection of data, but it is often more useful to think of an
array as a collection of variables of the same type.
• Array is a data structure that store a number of data items as a single entity (object) .
• The individual data items are called elements and all of them have same data types.
• Array is used when multiple data items have common characteristics are required.
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• Instead of declaring,
• such as number0, number1, ..., and number99,
• We declare one array variable such as numbers and use numbers[0],
numbers[1], and ..., numbers[99] to represent individual variables.
• A specific element in an array is accessed by an index.
• All arrays consist of contiguous memory locations.
• The lowest address corresponds to the first element and the highest
address to the last element.
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How to Define an Array?
• An Array is defined as following
<storage_class> <type-of-array> <name-of-array> [<number of elements in array>];
• storage_class: it may be auto, register, static and extern. [Optional]
• type-of-array: It is the type of elements that an array stores.
E.x. ‘char’, ‘int’.
• name-of-array: This is the name that is given to array. At least the name should
be in context with what is being stored in the array.
• [number of elements]: This value in subscripts [] indicates the number of
elements the array stores.
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For example (ONE DIMENSIONAL ARRAY)
• an array of five characters can be defined as :
• char arr[5];
• to declare a 10-element array called balance of type double:
• double balance[10];
• int num[35]; /* An integer array of 35 elements */
• char ch[10]; /* An array of characters for 10 elements */
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Initializing Array
• You can initialize an array in C either one by one or using a single statement as follows −
double balance[5] = {1000.0, 2.0, 3.4, 7.0, 50.0};
• The number of values between braces { } cannot be larger than the number of elements that we declare for
the array between square brackets [ ].
• If you omit the size of the array, an array just big enough to hold the initialization is created. Therefore, if you
write −
double balance[] = {1000.0, 2.0, 3.4, 7.0, 50.0};
• Ex: balance[4] = 50.0;
• The above statement assigns the 5th element in the array with a value of 50.0.
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• All arrays have 0 as the index of their first element which is also called
the base index and the last index of an array will be total size of the
array minus 1.
• Shown below is the pictorial representation of the array we discussed
earlier:
double balance[5] = {1000.0, 2.0, 3.4, 7.0, 50.0};
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Accessing Array Elements
• An element is accessed by indexing the array name.
• This is done by placing the index of the element within square
brackets after the name of the array. For example −
double salary = balance[4];
• The above statement will take the 10th element from the array and
assign the value to salary variable.
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example
#include <stdio.h>
int main () {
int n[ 10 ]; /* n is an array of 10 integers */
int i,j; /* initialize elements of array n to 0 */
for ( i = 0; i < 10; i++ ) {
n[ i ] = i + 100; /* set element at location i to i + 100 */
}
/* output each array element's value */
for (j = 0; j < 10; j++ ) {
printf("Element[%d] = %dn", j, n[j] );
}
return 0;
}
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[IMP] WAP to sort n numbers in ascending order.
#include <stdio.h>
int main(void){
int nums[50],i,j,n,temp;
printf("How many Numbers are there?t");
scanf("%d",&n);
printf("nEnter %d numbers: n",n);
for(i=0;i<n;i++){
scanf("%d",&nums[i]);
}
for (i = 0; i < n-1; ++i){
for (j=i+1; j < n;j++) {
if(nums[i]>nums[j]){
temp=nums[i];
nums[i]=nums[j];
nums[j]=temp;
}
}
}
printf("nThe numbers in ascending order:n");
for(i=0; i<n;i++){
printf("t%d",nums[i]);
}
printf("n");
}
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Characteristics Of An Array
• The declaration of int a[5] is nothing but creation of 5 variables of
integer type in the memory.
• All the elements of an array share the same name. distinguished from
one another by element number or array index.
• Any element can be modified separately without disturbing another
element.
• Element basis operation should be carried out rather than taking as a
whole.
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Questions (Classwork)
• WAP to read 10 integers from keyboard and display entered numbers
on the screen.
• WAP that reads mark’s percentage in an examination of 10 students
and deviation percentage from average of students.
• [IMP] WAP to find the highest and second last smallest number of an
element.
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Multi Dimensional Array
• Have more than one dimensions.
• Separate pair of square brackets is required for each subscript or
dimension or index.
• Two dimensional arrays will require two pairs of square brackets;
three dimensional with three pairs and so on.
• Two dimensional is also called matrix.
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storage_class data_type array_name[dim1] [dim2] … [dimn];
• Here, dim1,dim2…dimn are positive valued integer expressions that
indicate the number of array elements associated with each
subscript.
• m*n two dimensional array can be thought as tables of values having
m rows and n columns.
• For ex int x[3][3] can be shown as follows:
Col 1 Col 2 Col 3
ROW 1 X[0][0] X[0][1] X[0][2]
ROW 2 X[1][0] X[1][1] X[1][2]
ROW 3 X[2][0] X[2][1] X[2][2]
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Declaration of two-dimensional array
• Like one dimensional array, two dimensional arrays must also be
declared before using it.
• The syntax:
[storage_class] data_type array_name[row_size][col_size];
• Example:
• int matrix[2][3]; /* matrix is 2-D array which has 2 rows and 3 columns */
• float m[10][20];
• char students[10][15];
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Initialization of 2-D array
• int marks[2][3]={ {2,4,6}, {8,10,12} }; //is equivalent to
• marks[0][0]=2; marks[0][1]=4; marks[0][2]=6;
• marks[1][0]=8; marks[1][1]=10; marks[1][2]=12;
• int marks1[ ][3]= { {2,4,6}, {8,10,12} }; // is equivalent to
• marks1[0][0]=2; marks1[0][1]=4; marks1[0][2]=6;
• marks1[1][0]=8; marks1[1][1]=10; marks1[1][2]=12;
• int marks2[2][3]={2,4,6,8,10,12};
• Int marks3[][3]={2,4,6,8,10,12};
ERRORS:
• Int marks[3][]={2,4,6,8,10,12}; int marks[ ][ ]={2,4,6,8,10};
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Accessing 2-D array elements
• In 2-D array, the first dimension specifies number of rows and second
specifies columns.
• A row is 1-D array. 2-D array contains multiple rows(i.e. 1-D arrays).
Thus 2-D array is an array of 1-D arrays.
• 2-D array is traversed row by row(i.e. every column elements in first
row are traversed first and then column elements of second row are
traversed and so on.)
• Nested loop is used to traverse the 2-D array.
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• Let us consider following 2-D array marks of size 4*3
• i.e. matrix having 4 rows and 3 columns
• The Array is traversed in the following order:
35 ->10 ->11 ->34 ->90 ->76 ->13 ->8 ->5 ->76 ->4 ->1
• i.e marks[0][0] -> marks[0][1] -> marks[0][2] -> marks[1][0] ->
marks[1][1] -> marks[1][2] -> marks[2][0] -> marks[2][1] ->
marks[2][2] -> marks[3][0] -> marks[3][1] -> marks[3][2].
35 10 11
34 90 76
13 8 5
76 4 1
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#include <stdio.h>
int main(void){
int matrix[2][3],i,j;
for(i=0;i<2;i++){
for(j=0;j<3;j++){
printf("Enter Matrix[%d][%d]: ",i,j);
scanf("%d",&matrix[i][j]);
}
}
printf("The Entered Matrxn");
for(i=0;i<2;i++){
for(j=0;j<3;j++){
printf("%dt",matrix[i][j]);
}
printf("n");
}
}
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WAP: Sum of matrix
//FOR FIRST MATRIX A
for(i=0;<m;i++){
for(j=0;j<n;j++){
scanf(“%d”,&a[i][j]);
}
}
//FOR FIRST MATRIX B
for(i=0;<m;i++){
for(j=0;j<n;j++){
scanf(“%d”,&b[i][j]);
}
}
//FOR sum
for(i=0;<m;i++){
for(j=0;j<n;j++){
sum[i][j]=a[i][j]+b[i][j];
}
}
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Passing arrays to function
• It is possible to pass the value of an array element and even an entire
array as an argument to a function.
• To pass an entire array to a function, the array name must appear by
itself, without brackets or subscripts, as an actual argument in
function call statement.
• When declaring a one-dimensional array as a formal argument, the
array name is written with a pair of empty square brackets. The size
of the array is not specified within the formal argument declaration.
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• Syntax for function call passing array as argument,
function_name(array_name)
• Syntax for function prototype which accepts array
return_type function_name(data_type array_name[]);
Or
return_type function_name(data_type *pointer_variable);
• When array is passed to a function, the values of the array elements are
not passed to the function rather the array name is interpreted as the
address of the first array element.
• The address assigned to the corresponding formal argument when the
function is called.
• The formal argument therefore becomes a pointer to the first array
element.
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#include <stdio.h>
void display(int n){
printf("%dt", n );
}
int main(void){
int nums[5]={100,23,44,3,65},i;
printf("nThe content of array is: n");
for (int i = 0; i < 5; i++){
display(nums[i]);
}
}
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WAP to illustrate passing an entire array to a function
#include <stdio.h>
void change(int a[]){
a[0]=10;a[1]=20;a[2]=30;a[3]=40;a[4]=50;
}
int main(void){
int nums[5]={100,23,44,3,65},i;
printf("nBEFORE FUNCTION CALL: n");
for (int i = 0; i < 5; i++) {
}
printf("n");
change(nums); /* PASSING ARRAYS NUMS TO FUNCTION */
printf("nAFTER FUNCTION CALLn");
for (int i = 0; i < 5; i++) {
} printf("n");
}
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Arrays and Strings
• In C programming, array of character are called strings. A string is terminated by null
character 0. For example:
Ex. "c string tutorial"
• Here, "c string tutorial" is a string. When, compiler encounters strings, it appends null
character at the end of string.
• Strings are actually one-dimensional array of characters terminated by a null character
'0'.
• If you follow the rule of array initialization then you can write the above statement as
follows −
char greeting[] = "Hello";
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c s t r i n g t u t o r i a l 0

char greeting[] = "Hello";
Following is the memory presentation of the above defined string in C −
Actually, you do not place the null character at the end of a string constant. The C compiler automatically
places the '0' at the end of the string when it initializes the array.
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INDEX 0 1 2 3 4 5
VARIABLE H e l l o 0
ADDRESS 0x23452 0x23453 0x23454 0x23455 0x23456 0x23457

Initialization of strings
• In C, string can be initialized in different number of ways.
char c[]="abcd";
OR,
char c[5]="abcd";
OR,
char c[]={'a','b','c','d','0'};
OR;
char c[5]={'a','b','c','d','0'};
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C[0] C[1] C[2] C[3] C[4]
a b c d 0

Declaration of strings
• Strings are declared in C in similar manner as arrays. Only difference is
that, strings are of char type.
char s[5];
• Strings can also be declared using pointer.
char *p
(will be discussed in future chapters)
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s[0] s[1] s[2] s[3] s[4]

• Let us try to print the above mentioned string −
#include <stdio.h>
int main () {
char greeting[6] = {'H', 'e', 'l', 'l', 'o', '0'};
printf("Greeting message: %sn", greeting );
return 0;
}
OUTPUT:
Greeting message: Hello
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Write a C program to illustrate how to read string from terminal.
#include <stdio.h>
int main(){
char name[20];
printf("Enter name: ");
scanf("%s",name);
printf("Your name is %s.",name);
return 0;
}
OUTPUT:
Enter name: Dennis Ritchie
Your name is Dennis.
NOTE: Here, program will ignore Ritchie because, scanf() function takes only string before the white
space.
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C program to read line of text manually.
#include <stdio.h>
int main(){
char name[30],ch;
int i=0;
while(ch!='n') // terminates if user hit enter
{
ch=getchar();
name[i]=ch;
i++;
}
name[i]='0'; // inserting null character at end
printf("Name: %s",name);
return 0;
}
This process to take string is tedious. There are predefined functions gets() and puts in C language to read and display string respectively.
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int main(){
char name[30];
gets(name); //Function to read string from user.
printf("Name: ");
puts(name); //Function to display string.
return 0;
}
• Both, the above program has same output below:
• Output
Enter name: Tom Hanks
Name: Tom Hanks
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Passing Strings to Functions
#include <stdio.h>
void Display(char ch[]);
int main(){
char c[50];
printf("Enter string: ");
gets(c);
Display(c); // Passing string c to function.
return 0;
}
void Display(char ch[]){
printf("String Output: ");
puts(ch);
}
• Here, string c is passed from main() function to user-defined function Display(). In function
declaration, ch[] is the formal argument.
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C supports a wide range of functions that manipulate null-terminated strings −
S.N. Function & Purpose(these functions are defined in header file string.h)
1 strcpy(s1, s2);
Copies string s2 into string s1.
2 strcat(s1, s2);
Concatenates string s2 onto the end of string s1.
3 strlen(s1);
Returns the length of string s1.
4 strcmp(s1, s2);
Returns 0 if s1 and s2 are the same; less than 0 if s1<s2; greater than 0 if
s1>s2.
5 strchr(s1, ch);
Returns a pointer to the first occurrence of character ch in string s1.
6 strrev(s1);
Returns reverse of a string s1
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#include <stdio.h>
#include <string.h>
int main () {
char str1[12] = "Hello";
char str2[12] = "World";
char str3[12];
int len ;
/* copy str1 into str3 */
strcpy(str3, str1);
printf("strcpy( str3, str1) : %sn", str3 );
/* concatenates str1 and str2 */
strcat( str1, str2);
printf("strcat( str1, str2): %sn", str1 );
/* total lenghth of str1 after concatenation */
len = strlen(str1);
printf("strlen(str1) : %dn", len );
return 0;
}
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Strcpy(str3,str1) Hello
Strcat(str1,str2) HelloWorld
Strlen(str1) 10

Please do check Google
Drive for Assignment
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Reference
• http://www.thegeekstuff.com/2011/12/c-arrays/
• http://www.tutorialspoint.com/cprogramming/c_arrays.htm
• http://c.learncodethehardway.org/book/ex10.html
• http://beginnersbook.com/2014/01/c-arrays-example/
• A Textbook Of C programming by Ram Datta Bhatta
• http://www.cprogramming.com/tutorial/c/lesson9.html
• http://www.programiz.com/c-programming/c-strings
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Unit 6. Arrays

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Unit 6. Arrays