C language

27/march/2021

Things you cannot do

•You cannot

- use “=” to assign one array variable to another:

a = b; /* a and b are arrays */

-use “==” to directly compare array variables:

if (a==b) .……… . .

- directly scanf or printf arrays:

printf (“……”, a) ;

- The size may be omitted. In such cases, the compiler automatically allocates enough space for all initialized elements.

int flag [] = {1, 1, 1,0} ;

char name [] = {‘A’, ‘m’, ‘i’ , ‘t’ } ;

How to copy the elements of one array to another?

• By copying individual elements:

How to read the elements of an array?

By reading them one element at a time.

• The ampersand (&) is necessary.

• The elements can be entered all in one line or different lines.

How the print the elements of an array?

• By printing them one element at a time.

• The elements are printed one per line.

-The elements are printed all in one line.

Character string

Introduction

• A string is an array of characters.

-Individual characters are stored in memory in ASCII code.

- A string is represented as a sequence of characters terminated by the null (‘\0’) character.

Declaring string variable

• A string is declared like any other array:

char string-name [size] ;

-size determines the number of characters in string_name.

• When a character string is assigned to a character array, it automatically appends the null character (‘\0’) at the end of the string.

-Size should be equal to the number of characters in the string plus one.

Examples

char name [30] ;

char city [15];

char dob [11];

• A string may be initialized at the time of declaration.

Reading “words”

• scanf can be used with the “%s” format specification.

Char name [30] ;

Scanf (“%s”, name) ;

- The ampersand (&) is not required before the variable name with “%s”.

- The problem here is that the string is taken to be up to the first white space (blank, tab, carriage return, etc.)

- If we type “Rupak Biswas”

- Name will be assigned the string “Rupak”

Reading a “line of text”

• In many applications, we need to read in the entire line of text (including blank spaces).

• We can use the getchar() function for the purpose.

Writing strings to the screen

• We can use printf with the “%s” format specification.

Processing character strings

• There exists a set of C library functions for character string manipulation.

- strcpy :: string copy

- strlen :: string length

- strcmp :: string comparison

• It is required to add the line

#include <string.h>

Writing string to the screen

• We can use printf with the “%s” format specification.

25/march/2021

Basic concept

• Many applications require multiple data items that have common characteristics

• In mathematics, we often express such groups of data items in indexed form:

x1,x2,x3…..,xn

• Why are arrays essential for some applications?

- Take an example.

- Finding the minimum of a set of numbers.

Using Arrays

• All the data items constituting the group share the same name.

Int x[10];

• Individual elements are accessed by specifying the index.

Declaring Arrays

• Like variables, the arrays that are used in a program must be declared below they are used.

• General syntax:

type array-name [size];

- type specifies the type of element that will be contained in the array (int, float, char, etc.).

- size is an integer constant that indicates the maximum number of elements that can be stored.

• Example

int x[10];

char line[80];

float points[150];

char name [35];

• If we are not sure of the exact size of the array, we can define an array of a large size.

int marks [50];

char line [80];

float points[150];

char name[35];

• If we are not sure of the exact size of the array, we can define an array of a large size.

int marks[50];

though in a particular run we may only be using say, 10 elements.

• Starting from a given memory location, the successive array elements are allocated space in consecutive memory locations.

Array a

x x+k x+2k

X: starting address of the array in memory

K: number of bytes allocated per array element

• element a[i]:: allocated memory at the address x+ i*k

• First array index assumed to be at zero.

Accessing Array Elements

• A particular of the array can be accessed by specifying two things:

- Name the array.

- Index (relative position) of the element in the array.

• In C, the index of an array starts from zero.

• Example:

- An array is defined as int x[10];

- The first element of the array x can be accessed as x[0], the fourth element as x[3], tenth element as x[9], etc.

Contd.

• The array index must evaluate to an integer between 0 and n-1 where n is the number of elements in the array.

a[x+2] = 25;

b[3*x-y] = a[10-x]+5;

A Warning

• In C, while accessing array elements, array bounds are not checked.

• Example:

int marks[5];

• Example:

int marks[5];

marks[8] = 75

- The above assignment would not necessarily cause an error.

- Rather, it may result in unpredictable program results.

Initialization of Arrays

• General form:

type array_name [size] = { list of values } ;

• Examples:

int marks [5] = {72, 83, 65, 80, 76};

char name [4]= {‘A’, ‘m’, ‘i’, ‘t’ };

• Some special cases:

- if the number of values in the list is less than the number of elements, the remaining elements are automatically set to zero. float total [5] = {24.2, -12.5, 35.1};

total [0] = 24.2, total [1] =-12.5, total [2] = 35.1,

total [3] = 0, total [4] = 0

Contd.

-The size may be omitted. In such cases, the compiler automatically allocates enough space for all initialized elements.

Int flag [ ] = {1, 1,1,0};

char name[ ] = { ‘A’, ‘m’, ‘i’, ‘t’, };

Example 1: Find the minimum of a set of 10 numbers

Alternate Version 1

# include < stdio.h >

# include < conio.h>

Main (void )

{

int a,b,c;

printf (“sum-1 \n, sub-2\n, multi-3\n, div-4\n, mod-5\n”);

printf (“Enter the choice : \n”);

scanf (“%d “ ,&a,&b);

If (c==2)

Sub = a-b;

Else if (c==3)

Multiply =a*b;

Else if (c ==4)

Divide =a/b;

Else if (c == 5)

Mod = a%b;

Getch();

}

• We can use any level of nesting with the switch case statement.

• Default:- When no case is matched, at that level default is executed.

• We can use any loop inside the switch case statement.

How we can use char data with switch case

# include(stdio.h)

#include (canio.h)

void main ()

int a,b,x,y;

char c;

printf (“sum = a.A + \n, sub = S.s,-\n,

multiply = m.M,*\n,div = d.D/ \nl;

printf ( “Enter two integer values” );

scanf ( “ %d %d” , &a,&b );

printf ( “ Enter choice in character for sum, sub, multiply divide”);

f flush (stdin);

// use at before reading the character data

//used to clear input buffer.

Scanf (“/c” , &c );

Switch (c)

{

case ‘a’;

case ‘A’; case ‘t’; x = a+b; break; • We enter in switch case which we want to check Case ‘s’; Case ‘r’; case ‘*’; x= a*b, break; case ‘d’; case ’D’; case ‘I’; switch (b) { case o : printf ( “wrong data”); printf ( “Denominator is zero”); printf ( “Enter non zero value for denominator”); scanf (“%d” ,&b ); x=a/b; break; default, x = a/b; } break; default { printf ( “result = %d”,x);