The document provides an overview of arrays in C programming, detailing their definition, characteristics, and methods of declaration and initialization. It includes examples of one-dimensional and two-dimensional arrays, how to access elements, and how to pass arrays to functions. The document also touches on the representation of strings as arrays of characters in C, including initialization and input/output functions for strings.

1. UNIT 6
ARRAYS

2. 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.
Ashim Lamichhane 2

3. • 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.
Ashim Lamichhane 3

4. 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.
Ashim Lamichhane 4

5. 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 */
Ashim Lamichhane 5

6. 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.
Ashim Lamichhane 6

7. • 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};
Ashim Lamichhane 7

8. 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.
Ashim Lamichhane 8

9. 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;
}
Ashim Lamichhane 9

10. [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");
}
Ashim Lamichhane 10

11. 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.
Ashim Lamichhane 11

12. 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.
Ashim Lamichhane 12

13. 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.
Ashim Lamichhane 13

14. 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]
Ashim Lamichhane 14

15. 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];
Ashim Lamichhane 15

16. 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};
Ashim Lamichhane 16

17. 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.
Ashim Lamichhane 17

18. • 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
Ashim Lamichhane 18

19. #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");
}
}
Ashim Lamichhane 19

20. 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];
}
}
Ashim Lamichhane 20

21. 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.
Ashim Lamichhane 21

22. • 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.
Ashim Lamichhane 22

23. #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]);
}
}
Ashim Lamichhane 23

24. 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("t%d",nums[i]);
}
printf("n");
change(nums); /* PASSING ARRAYS NUMS TO FUNCTION */
printf("nAFTER FUNCTION CALLn");
for (int i = 0; i < 5; i++) {
printf("t%d",nums[i]);
} printf("n");
}
Ashim Lamichhane 24

25. 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";
Ashim Lamichhane 25
c s t r i n g t u t o r i a l 0

26. 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.
Ashim Lamichhane 26
INDEX 0 1 2 3 4 5
VARIABLE H e l l o 0
ADDRESS 0x23452 0x23453 0x23454 0x23455 0x23456 0x23457

27. 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'};
Ashim Lamichhane 27
C[0] C[1] C[2] C[3] C[4]
a b c d 0

28. 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)
Ashim Lamichhane 28
s[0] s[1] s[2] s[3] s[4]

29. • 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
Ashim Lamichhane 29

30. 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.
Ashim Lamichhane 30

31. C program to read line of text manually.
#include <stdio.h>
int main(){
char name[30],ch;
int i=0;
printf("Enter name: ");
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.
Ashim Lamichhane 31

32. int main(){
char name[30];
printf("Enter name: ");
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
Ashim Lamichhane 32

33. 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.
Ashim Lamichhane 33

34. 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
Ashim Lamichhane 34

35. #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;
}
Ashim Lamichhane 35
Strcpy(str3,str1) Hello
Strcat(str1,str2) HelloWorld
Strlen(str1) 10

36. Please do check Google
Drive for Assignment
Ashim Lamichhane 36

37. 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
Ashim Lamichhane 38

38. END
Ashim Lamichhane 39