Difference between revisions of "C-and-C++/C3/Strings/English"

Learning Objectives

What is a string.

Declaration of a string.

Initialization of a string.

Few examples on string.

We will also see some common errors and their solutions

System Requirements

Ubuntu Operating System version 11.04

gcc and g++ Compiler version 4.6.1

Introduction to strings

String is a sequence of characters that is treated as a single data item

size of string = length of string + 1

Declaration of the String

Syntax:

char val[10];

The syntax for this is

char name_of_string[size];

char, name of string and size

char is the data type, name of the string is the string name, and we can give the size here.

Eg: here we have declared a character string names with size 30

I have already typed the program

I will open it

Note that our file name is string.c

In this program we will take a string as an input from the user and print it

Let me explain the code now

#include<string.h>

here string.h includes the declarations, functions, constants of string handling utilities

Whenever we work on string functions, we should include this header file

char strname[30];

Here we are declaring the string 'strname' with size '30'

printf("Enter the string\n");

scanf("%[^\n]s",strname);

We are using the caret sign and \n to include the spaces with the string

printf("The string is %s\n", strname);

And this is our return statement

On the terminal

Please open the terminal window by pressing Ctrl, Alt and T keys simultaneously on your keyboard

gcc strdeclare.c str

>> press Enter

Type

gcc space string.c space -o space str

And press Enter

./str

>> press Enter

type

./str

now press Enter

Talk To A Teacher >> press Enter

Talk To A Teacher

now press Enter

Output

The string is Talk To A Teacher

Initialization of the string

Syntax:

char strinitialize[20] = “star”;

(or)

char strinitialize[] = {'S', 't', 'r'};

Until now we discussed about the declaration of a string

Now we are going to discuss how to initialize the string

The syntax for this is

char var_name[size] = “string”;

eg: here we have declared a character string names with size 30 and the string is Priya

Another syntax is

char var_name[ ] = {'S', 't', 'r', 'i', 'n', 'g'}; within single quotes

eg: char names[10] = {'P', 'r', 'i', 'y', 'a'}; in single quotes

Switch back to our Editor

We will use the same example

File >> Save as option

Type

strinitialize.c

now save the file with the name strinitialize.c

char name[30] = "Talk To A Teacher";

Hence at the 5th line type

= and within double quotes “Spoken- Tutorial”;

now click on save

printf("Enter the string\n");

scanf("%[^\n]s",strname);

as we are only going to print the string

click on save

Type

gcc strinitialize.c -o str1

To compile

Type

gcc space stringintialize.c space -o space str2

Type

./str1

now press Enter

To execute type ./str2

Output

The string is Spoken-Tutorial

Type

sting.h

Come back to our program

Suppose here we type the spelling of string as

sting

gcc strinitialize.c -o str1

./str1

We see a fatal error

sting.h no such file or directory

compilation terminated

This is because the compiler is not able to find the header file with the name sting.h

Hence it is giving an error

Let us fix the error

Type r here

now click on save

Come back to our terminal

Compile as before, execute as before

Yes it is working!

Type

int

come back to our program

Suppose here I will type int in place of char

now click on save

Let us see what happens

Come back to our terminal

Compile as before

We see an error

Wide charactr array initialized from non-wide string

format %s expects argument of type 'char'

But argument 2 has type 'int'

come back to our program

this is because we used %s as the format specifier for string

And we are initializing it with an integer data type int

Type 'char' here

click on save

let us execute

Compile as before, execute as before

Come back to our program

Save as

Type

.cpp

We will edit the code here

First press shift, cntrl and S key simultaneously on your keyboard

Now save the file with an extension .cpp

and click on save

iostream

iostream

#include <string>

now click on save

now we will delete this declaration

string strname;

Click on save

cout <<

delete the closing bracket here

Type

getline(cin, strname);

Type

getline(cin, strname) at the end type a ;

cout <<"The string is " <<strname <<"\n";

In place of

printf("The string is %s\n",strname);

Delete the format specifier and \n

Now delete the ,

Type two opening angle brackets, delete the bracket here

type two opening angle brackets and within the double quotes type \n

since we do not use the format specifier in C++

the compiler should know that strname is a string variable

Here we use getline to extract the characters from the input sequence, it stores them as a string

g++ string.cpp -o str1

g++ space string.cpp space -o space str3

and press Enter

./str1

./str3

Press enter

I will enter as Talk To A Teacher

Now press Enter

The string is Talk To A Teacher

We can see that the output is similar to our C code

Now come back to our slides

In this tutorial we learnt

Strings

• Declaration of a string

eg: char strname[30]

• Initialization of a string

eg: char strname[30] = “Talk To A Teacher”

Assignment

Write a program to print a string using the 2^nd syntax

About the Spoken Tutorial Project

http://spoken-tutorial.org /What\_is\_a\_Spoken\_Tutorial

It summarises the Spoken Tutorial project

If you do not have good bandwidth, you can download and watch it

Spoken Tutorial Workshops

Conducts workshops using spoken tutorials

Gives certificates to those who pass an online test

For more details, Please write to

contact@spoken-tutorial.org

Acknowledgement

It is supported by the National Mission on Education through ICT, MHRD, Government of India

More information on this Mission is available at: http://spoken-tutorial.org\NMEICT-Intro

Thank You for joining