Session 4

ARRAY in C • Array is a collection or group of similar data type

elements stored in contiguous memory.

• The individual data items can be characters, integers, floating points numbers and so on .

• Here contiguous memory allocation means array occupies contiguous bytes as needed in the memory.

Declaring single dimension Arrays

• We can declare an array by specify its data type, name and the number of elements the array holds between square brackets immediately following the array name.

• Here is the syntax:data_type array_name[size];

Declaring single dimension Array• For example, to declare an integer array which

contains 10 elements we can do as follows:

int values[10];

Accessing Single Dimension Array• We can access array elements via

indexes array_name[index]. Indexes of array starts from 0

• With each subscript enclosed in square brackets.

• For example,values[0]=5;values[1]=10;printf(“%d”,values[1]);

Initializing Arrays• It is like a variable, an array can be initialized.

• To initialize an array, you provide initializing values which are enclosed within curly braces in the declaration and placed following an equals sign after the array name.

• Here is an example of initializing an integer array.

int list[5] = {2,1,3,7,8};

Multi dimensional Arrays:• Often there is a need to store and manipulate two

dimensional data structure such as matrices & tables.

• Here the array has two subscripts. One subscript denotes the row & the other the column.

• The declaration of two dimension arrays is as follows:data_type array_name[row_size][column_size]; int m[10][20];

Declaring Multi Dimensional Arrayfloat table [50][50]; char page[50][50];

int num[3][3]; 0 1 2012

Accessing two dimensional arraysint values[2][2];values[0][0]=1; values[0][1]=2;values[1][0]=3; values[1][1]=4;

int num[2][2]={1,2,3,4};int matrix[3][3] ={{11,12,13}, {21,22,23}, {32,31,33}};

ARRAY AND STRINGS • The gets and puts functions:

• The gets and puts functions facilitate the transfer of strings between the computer and the standard input/output devices.

• Each of these functions accepts a single argument. The argument must be a data item that represents a string(e.g. character array).

Example of using gets and puts#include<stdio.h> void main() {

char inne[80]; gets(line); puts(line);

} The gets and puts functions offer simple alternatives to the use of scanf and printf for reading and displaying strings

String library functions• strlen() • This function counts a number of characters

present in a string while giving a call to the function.

char msg[] = “Lord krishna”; int n; n=strlen(msg); printf(“length of string =%d”, n);

• strcpy() • This function copies the contents of one string

to another. • The base address of source and target strings

are supplied to the function.

char source[] = “Lord Krishna”; char target[15]; strcpy(target, source); printf(“Source string is : %s”, source); printf(“target string is :%s”,target);

String library functions

• strcat() • This function concatenates the source string

at the end of target sting. char s[] = “Lord”; char t[] = “Krishna”; strcat(t,s); printf(“source string is %s\n”, s); printf(“target stirng is %s\n”, t);

String library functions

String library functions• strcmp() • This function compares two strings and returns some

integer value. • If both the strings are equal then it returns 0 otherwise

it returns some other integer value.void main() {

char s1[]=”Jerry”; char s2[]=”Ferry”; int j= strcmp(s1, s2); printf(“%d”, j);

}

Understanding Functions• What is Function?• A function in C language is a block of code that

performs a specific task.

• It is reusable i.e. it can be executed from as many different parts in a C Program as required.

• It also optionally returns a value to the calling program

Structure of a Function<return type> FunctionName (Argument1, Argument2, Argument3……){

Statement1;Statement2;

}int sum (int x, int y){

int result;result = x + y;return (result);

}

Types of functions:A function may belong to any one of the following categories:

• Functions with no arguments and no return values.

• Functions with arguments and no return values.• Functions with arguments and return values.• Functions that return multiple values.• Functions with no arguments and return values.

Advantages of using functions:• It makes possible top down modular

programming.

• The length of the source program can be reduced.

• It becomes uncomplicated to locate and separate a faulty function for further study.

• c programmer can use function written by others, instead of starting over from scratch.

Function Example#include <stdio.h>void printMessage (){

printf ("Programming is fun.\n");}void main (){

printMessage ();}

Function Which Return Values#include <stdio.h>int add (int x,int y){

int result; result=x+y;return(result);

}void main (){

int total;total=add(10,12);

}

Recursive Function• Recursive function is a function which

contains a call to itself.

• Recursive function allows you to divide your complex problem into identical single simple cases which can handle easily.

• This is also a well-known computer programming technique: divide and conquer.

Example of recursive function# include<stdio.h>int factorial(int number){

if(number <= 1) return 1; return number * factorial(number - 1);}void main(){ int x = 5; printf("factorial of %d is %d",x,factorial(x));}

Scope Rule of Functions void main( ) {

int i = 20 ; display ( i ) ;

} void display ( int j ) {

int k = 35 ; printf ( "\n%d", j ) ; printf ( "\n%d", k ) ;

}