Chapter 3

Input and Output in C++

3.1  INTRODUCTION

Computer applications generally involve tremendous amount of data to be read from input devices and sending them to the output devices. Hence, to control such operations, every programming language provides a set of inbuilt functions. C++ supports all input/output (I/O) functions of C. C++ also has library functions. A library is a set of .obj files, which is linked to the program and gives additional beneficial support with its functions. The programmer can use the library functions in the programs. The library is also called as iostream library. The difference between C and C++ I/O function is that C functions do not support object-oriented platform whereas C++ supports object-oriented platform.

3.2  STREAMS IN C++ AND STREAM CLASSES

The C++ supports a number of I/O operations to perform read and write operations. These C++ I/O functions help the user to work with different types of devices such as keyboard, disk, tape drivers, etc. Stream is an inter-mediator between I/O devices and the user. The standard C++ library contains the I/O stream functions. The I/O functions are part of the standard library that provides portability to the language itself. A library is a set of .obj files connected to the user’s program.

The stream is a flow of data, measured in bytes, in sequence. If data is received from input devices in sequence, then it is called as source stream, and when the data is passed to output devices, then it is called as destination stream. This process of flow of data is also known as encapsulation through streams. The data is received from the keyboard or disk and can be passed to the monitor or to the disk. Figure 3.1 describes the concept of stream with input and output devices.

Fig. 3.1 Streams and I/O devices

The data in source stream can be used as input data by the program. So, the source stream is also called as input stream. The destination stream that collects output data from the program is known as the output stream. The mechanism of the input and output stream is illustrated in Figure 3.2.

Fig. 3.2 C++ input and output streams

As discussed earlier, the stream is an inter-mediator between I/O devices and the user. The input stream receives data from keyboard or storage devices such as hard disk, floppy disk, etc. The data present in output stream is passed on to the output devices such as monitor or printer according to the user’s choice.

3.3  PRE-DEFINED STREAMS

C++ has a number of pre-defined streams. These pre-defined streams are also called as standard I/O objects. These streams are automatically activated when program execution starts. Table 3.1 describes the pre-defined streams.

 

Table 3.1 Pre-defined C++ Stream or I/O Global Objects

cin	Standard input, usually keyboard, corresponding to stdin in C. It handles input from input devices usually from keyboard.
cout	Standard output, usually screen, corresponding to stdout in C. It passes data to output devices such as monitors and printers. Thus, it controls output.
clog	A fully buffered version of cerr (no C equivalent). It controls error messages that are passed from buffer to the standard error device.
cerr	Standard error output, usually screen, corresponding to stderr in C. It controls the unbuffered output data. It catches the errors and passes to standard error device monitor.

 

Explanation: In this program the pre-defined objects cout, cerr, and clog are used to display the message “STREAMS” on the screen.

3.4  BUFFERING

It is a block of memory used to hold data temporarily. It is always located between a peripheral device and a faster computer. Buffers are used to pass data between computer and devices. The buffer increases the performance of the computer by allowing read/write operation in larger chunks. For example, if the size of the buffer is N, the buffer can hold N number of bytes of data.

Writing data to the disk is very costly. The read/write operation with disk takes a long time. When these operations are carried out, the execution of the program will be slow for few seconds. If the program involves many read and write operations, the program execution speed will be slower. To avoid this problem, the stream provides buffer. Buffer holds the data temporarily. The input data is passed to the stream buffer. The data is not written to the disk immediately till the buffer fills. When the buffer is completely filled, the data is written to the disk. This is explained with an example in Figure 3.3.

Fig. 3.3 Working of buffer

In Figure 3.3a, the level of the steam in the pressure cooker is increasing. The steam is not full, hence the whistle will not blow, and the steam will not be released from the pressure cooker.

In Figure 3.3b, the pressure cooker is completely filled. The level of the steam reaches to the top. Due to high-pressure the whistle blows automatically and the steam comes out of the pressure cooker.

After the steam comes out the whistle falls down. Even when the cooker is not completely filled with steam, the steam can be released manually by pulling up the whistle. It is just like flushing the buffer even when the buffer is not completely filled.

3.5  STREAM CLASSES

C++ streams are based on class and object theory. C++ has number of classes that work with console and file operations. These classes are known as stream classes. Figure 3.4 shows the stream classes. All these classes are declared in the header file iostream.h. The file iostream.h must be included in the program, if we are using the functions of these classes.

As described in Figure 3.4a the classes istream and ostream are derived classes of base class ios. The ios class contains member variable object streambuf. The streambuf places the buffer. The member function of streambuf class handles the buffer by providing the facilities to flush clear and pour the buffer. The class iostream is derived from the classes istream and ostream by using multiple inheritance. The ios class is a virtual class and it is present to avoid ambiguity that frequently appears in multiple inheritance. Chapter 11 describes multiple inheritance and virtual classes.

Fig. 3.4 Hierarchy of stream classes

The ios class has an ability to handle formatted and unformatted I/O operations. The istream class gives support for both formatted and unformatted data. The ostream classes handle the formatting of output data. The iostream contains functions of both istream and ostream classes. The classes istream_withassign, ostream_withassign, and iostream_withassign append appropriate assignment operators as shown in Figure 3.4b. Table 3.2 describes functions/contents of C++ stream classes.

 

Table 3.2 Functions/Contents of C++ Stream Classes

Class	Function/Contents
ios	It is an input and output stream class. It is used to implement a buffer, i.e. it is pointer to a buffer streambuf. ios maintains the information on the state of streambuf, i.e. good, bad, eof, etc.
istream	istream provides formatted input. It is used to handle formatted as well as unformatted conversion of character from a streambuf. The properties of ios are inherited in istream class. The instance of class does not carry out the actual input. istream declares functions such as peek(), tellg(), seekg(), getline(), read(), etc. istream class overloads the ‘>>’ operator.
ostream	It is used for general-purpose output. It is used to declare the output functions such as tellp(), put(), write(), seekp(), etc. It is the parent of all output stream. ostream overloads the ‘<<’ operator.
iostream	It is used to handle both input and output streams.
istream_withassign	It is derived from istream. It is used for cin input.
iostream_withassign	It is a bidirectional stream.

3.6  FORMATTED AND UNFORMATTED DATA

Formatting means representation of data with different settings as per the requirement of the user. The various settings that can be done are number format, field width, decimal points, etc.

The data accepted or printed with default setting by the I/O function of the language is known as unformatted data. For example, when the cin statement is executed, it asks for a number. The user enters a number in decimal. For entering decimal number or displaying the number in decimal using cout statement, the user will not need to apply any external setting. By default, the I/O function represents the number in decimal format. Thus, the data handled in such a way is called as unformatted data.

If the user needs to accept or display data in hexadecimal format, manipulators with I/O functions should be used. The data obtained or represented with these manipulators are known as formatted data. For example, if the user needs to display the data in hexadecimal format, then the manipulator can be used as follows.

cout<<hex<<15;

The above statement converts decimal 15 to hexadecimal F.

3.7  UNFORMATTED CONSOLE I/O OPERATIONS

Input and Output Streams

The input stream uses cin object to read data and the output stream uses cout object to display the data on the screen. The cin and cout are pre-defined streams for input and output data. The data type is identified by these functions using operator overloading of the operators << (insertion operator) and >> (extraction operator). The operator << is overloaded in ostream class and the operator >> is overloaded in istream class. Figure 3.5 shows the flow of input and output stream.

Fig. 3.5 Working of cin and cout statements

Input Stream

The input stream reads operation through keyboard. It uses cin as object. The cin statement uses >> (extraction operator) before a variable name. The cin statement is used to read data through the input device. Its syntax and example are as follows.

Syntax:

cin>>variable;

Example:

int v1;

float v2;

char v3;

cin>> v1>> v2>> v3…>> vn;

where v1, v2, and v3 are variable names. The response of the user to this statement would be as shown below.

2 5.4 A // input data

If the user enters data in the manner 2 5.4 A, then the operator will assign 2 to v1, 5.4 to v2 and A to v3. If the entered data is greater than the variable, it remains in the input stream. While entering string, blank spaces are not allowed. More than one variable can be used in cin statement to input data. Such operations are known as cascaded input operations.

For example,

cin>>v1>>v3;

where v1 and v2 are variables.

The operator >> accepts the data and assigns it to the memory location of the variables. Each variable requires >> operator. Both these statements should not be included in the bracket. The enter data is separated by space, tab, or enter. Similar to scanf() statement, cin does not require control strings such as %d for integer, %f for float, etc.

More examples

int weight;

cin>>weight // Reads integer value

float height;

cin>>height; // Reads float value

double volume;

cin>>volume; // Reads double value

char result[10];

cin>>result; // Reads char string

Output Streams

The output streams manage output of the stream, that is, display contents of variables on the screen. It uses << insertion operator before the variable name. It uses the cout object to perform console write operation. The syntax and example of cout statement are as follows.

Syntax:

cout<<variable

Example:

cout<<v1 <<v2 <<v3 … <<vn;

where, v1, v2, and v3 are variables. The above statement displays the contents of these variables on the screen. The syntax rules are similar to cin. Here, the cout statement uses the insertion operator <<. The cout statement does not use the format specification such as %d, %f as used in C, etc. The cout statement allows us to use all ‘C’ escape sequences such as ‘ ’, ‘ ’, etc.

More examples

int weight;

cout<<weight // Displays integer value

float height;

cout<<height; // Displays float value

double volume;

cout<<volume; // Displays double value

char result[10];

cout<<result; // Reads char string

The table given below illustrates comparative programs on cout statements.

 

 

Explanation: In the above program, cout statement displays a given string on the screen. It is similar to printf() statement. The cin statement reads data through the keyboard. It is similar to scanf() statement.

 

Explanation: In the above program, the cin statement reads two integers in variables num and num1. The cout statement displays the read numbers. The escape sequence ‘ ’ is used to insert tab between two numbers.

 

Explanation: Explanation of each of the cout statement is as follows.

1. cout<<“================” – Displays line of on the screen.
2. cout<<endl – Breaks a line.
3. cout<<“Hello” – Display string “Hello” on the screen.
4. cout<<“ ” – Breaks a line.
5. cout<<123; – Displays integer 123.
6. cout<<endl<<3.145 – Breaks a line and displays float number 3.145.
7. cout<<endl<<“NUMBER: ”<<“ ”<< 452 – Breaks a line, displays the string “number”, inserts a tab and integer number 452.
8. cout<<“ ==== The end =====” – Displays the line and string.

Explanation: In the above program, the statement cout<<“x = ”<<x <<“ y =”<<y <<“ z = ”<<z <<endl displays values of x, y, and z. The statement cout<<“City = ”<<city displays the contents of character array city.

 

Explanation: Explanation of the program is as follows.

1. cout<<“ Enter integer, float, and char” – Prompts message “Enter integer, float, and char”
2. cin>>x>>y>>z – Accepts integer, float, and char and stores in x, y, and z.
3. cout<<“ Enter a string: ” – Displays message “Enter a string: ”.
4. cin>>city – Reads string through the keyboard and stores in the array city[15].
5. cout<<“City = ”<<city; – Displays contents of the array city.

3.8  TYPE CASTING WITH THE cout STATEMENT

Type casting refers to conversion data of one basic type to another by applying external use of data type keywords. The description of type casting is explained in Chapter 3. Programs on type casting are as follows.

 

Explanation: In the above program, the variables of int float, double, and char type are declared and initialized. The variable a is initialized with 66, f with 2.5, d with 85.22, and c with character ‘K’.

The first cout statement converts integer value to the corresponding character according to the ASCII character set and the character B is displayed.

The second cout statement converts float value to integer. The value displayed is 2 and not 2.5. When type cast format (int) is used, the decimal portion of float value is removed and only the integer part is considered.

In the third statement, the double value is converted to character. The number 85.22 is converted to integer and then to character. The char data type is nothing else than int data type. The only difference is that the char data type has range from −128 to 127, which requires one byte in the memory.

The last statement converts character to int. The value of ‘K’ is 75 when printed as an integer. The format (int) converts char to int.

Fig. 3.6 Typecasting integer

In Figure 3.6, 65 is an integer and it is converted to character A by using type casting format (char). Table 3.3 describes various type casting formats and their output results.

 

Table 3.3 Type Casting Formats

Type Casting Formats	Outputs	Conversion
cout<< (char)65;	A	int to char
cout<< (int)‘A’;	65	char to int
cout<< (int)5.22;	5	float to int
cout<< (char)78.33;	N	float to char
cout<<(double) 123445338.33;	1.234453e+08	float to double
cout<< (unsigned)-1;	65535	signed to unsigned

 

Explanation: Consider the following statements.

 

int x=77 – Declares integer variable x and initializes it with 77.

float y=5.1252 – Declares float variable y and initializes it with 5.1252.

char z=‘A’; – Declares character variable z and initializes it with character ‘A’.

 

The following statements are used to display the contents on the screen.

 

	cout<<“ x = ”<<(char) x<<endl	–Variable x is an integer but value displayed will be ‘M’ because the statement (char) converts integer to the corresponding ASCII character.
	cout<<“ y = ”<<(int)y <<endl	–Variable y is a float but before printing the value 5.1252, it is converted to integer and the output will be 5.
	cout<<“ z = ”<<(int)z	–Variable z is of character type. The character value is converted to integer and the output displayed will be 65.

 

Explanation: In the above program, A to Z alphabets are displayed using cout() and printf() statements. In cout() statement before printing, type casting is done. The integer is converted to corresponding char type symbol and displayed. In the printf() statement, the control string %c performs this task. The quotation mark (“ ” ) inserts space between two successive characters.

 

Explanation: The cout statement displays the address of a variable in hexadecimal format. Using type casting, syntax (unsigned) converts hexadecimal to unsigned integer (decimal). The output shows addresses in both hexadecimal and unsigned integer (decimal) formats.

The & (ampersand) operator is used to display the address of the variable. The address operator is preceded by the variable name. The address is always represented as an unsigned integer. The cout statement displays the address in hexadecimal format. To convert the hexadecimal address to an unsigned integer, type casting is used.

 

Explanation: In the above program, the character pointer name is assigned to the string “c plus plus”. The first cout statement displays the string using variable name. The statement cout<<&name[0]<<“ ” displays the string. Here, & operator is used and the 0 (zero) points to the base address of the string. In the second statement, if the base address is not specified, then it will display the address. The third statement uses the pointer notation to display the string.

 

Explanation: In the first statement, the operators * and & are used one after another and the variable name is inside the parentheses. In the second statement, operator & is outside and the operator * and variable name are inside the parentheses. In the third statement, parentheses are not used. All the three statements display the output “c plus plus.”

3.8.1  Difference of Using C and C++ I/O Functions

The printf() and scanf() of C language needs format string. For example, to read and display an integer, the scanf and printf() statement can be written as follows.

 

int x;

scanf (“%d”,&x)

printf (“%d”,x);

 

In the above statements, %d is used to tell the I/O functions to treat the data as integer.

If the integer x is changed to long integer, the programmer needs to change every occurrence of %d in the program with %ld.

The C++ statement reads and displays the same data as follows.

 

int x;

cin>>x;

cout<<x;

 

Here, the cin and cout statements do not require any format string. If the type of x is changed to long integer, the user need not specify the type of data or any correction in the statement. The cin and cout statement identifies the data type. The format of cin and cout statement is the same for all types of variables.

get() and put() functions

get() function

The single character input and output operations in C++ can be done using put() and get() functions. The classes istream and ostream provide the two member functions put() and get(). The get() is used to read a character and put() is used to display the character on the screen.

The get() function has two syntaxes:

1. get(char*);
2. get(void);

If syntax (a) is used, the get() function assigns the read data to its argument, whereas when the statement (b) is used, the get() function returns the data read. The data is assigned to the variable present on the left-hand side of the assignment operator. These functions are members of I/O stream classes and can be called using object.

put() function

The put() function is used to display the string on the screen. It is a member of ostream class. The syntax of put() is as follows:

 

1. cout.put (‘A’);
2. cout.put (x);

 

The statement (a) displays the character ‘A’ on the screen and the statement (b) displays the contents of variable x on the screen. If an integer is used as an argument, its corresponding ASCII value is displayed. Few examples are illustrated below.

 

Explanation: The cout.put() statement displays one character at a time on the screen. In this program, three characters are displayed on the screen using cout.put() statement.

 

Explanation: The escape sequences such as ‘ ’, ‘ ’, etc., can be used with cout.put() statement. The escape sequences are combinations of two characters. The output of the program displays the number 1 and 2 in two separate lines. The statement cout.put(‘ ’) splits a line.

 

Explanation: In the above program, the single object cout is used followed by sequence of put() statement. The put() statements are separated by dot operators. In this way, multiple statements can be combined.

 

Explanation: In the above program, character variable ch is declared. The first cout statement displays message “Enter a character:” on the screen. The cin.get() function activates input stream and character entered by the user is stored in the variable ch. The cout.put() statement displays the character on the screen.

 

Explanation: In the above program, a character array ch[3] is declared. The sequence of get() and put() functions are used to read and display the characters. The get() function reads characters and stores in array ch[3]. The put() function displays the same on the screen.

 

Explanation: In the above program, the character array x[] is declared. The first while loop reads characters using cin.get() function through the keyboard. When a user presses the enter key, the while loop terminates. The second while loop displays the characters read using the function cout.put(). The output of the program is as shown above.

getline() and write() functions

getline() function

The getline() and write() functions are useful in string input and output. The getline() functions read the string including white space. The cin() function does not allow to enter the string with blank spaces. The input reading is terminated when a user presses the enter key. The new line character is accepted but not saved and replaced with the null character. The object cin calls the function as follows.

 

cin.getline (variable, size);

 

where the variable name may be any character array name and the size is the size of the array.

write() function

The write() function is used to display the string on the screen. Its format is similar to getline() function, but the function is exactly the opposite. The syntax is as follows.

 

cout.write (variable, size);

 

where the variable name may be a character type and size is the size of the character arrays. The cout.write() statement displays only a specified number of characters given in the second argument, though the actual string may be more in length. If the size of the array is larger than the actual string length, then the size argument contains the actual size of the array. In this case, the getline() displays blank spaces for the remaining unfilled elements. The following program illustrates both the functions.

 

Explanation: In this program, the first statement displays “INDIA” followed by one blank space. This is because the argument value is greater by one than the actual string length.

Similarly, the second statement displays “IS” followed by one blank space. The reason is same.

The last statement displays “GREAT.” Here, the argument value and the string lengths are same. Hence, no blank spaces are displayed.

In case the argument value is less than the actual string length, the complete string will not be displayed. The number of characters of the string displayed depends on the value of the given argument.

 

Explanation: In the above program, the cout.write() will not display the complete string. The statement displays the characters according to the value of the second argument. The value of the second argument is three. Hence, instead of six characters only three characters are displayed and the remaining characters are skipped.

 

Explanation: In the above program, the x[] is a character array. The getline() function reads the string through the keyboard. The getline() function accepts the string including spaces. The cout() statement displays the string including white spaces. The first write() statement displays the string with garbage values. This is because the string length is less than the actual size of the array. In the second write() statement, strlen() function calculates the length of the string and that length is used as an argument in the write() statement. This statement displays the entered string without any garbage collection.

The cin() statement cannot accept a string including spaces. It accepts only a single word. The cout() statement displays the string read through cin() and getline() functions, that is, it can display the string with or without blank spaces. The write() statement displays the string according to the specified size. It displays the string with or without blank spaces. The write() does not support any escape sequence.

 

Explanation: In the above program, two strings are entered in character arrays x[] and a[]. The successive write() statement in one line displays the string one after another. Thus, we can use multiple write() statements followed by a single cout object.

3.9  MEMBER FUNCTIONS OF THE ISTREAM CLASS

The istream contains the following functions that can be called using cin object.

peek(): It returns the succeeding character without extraction. For example,

 

cin.peek()==‘#’;

 

where cin is an object and ‘#’ is the symbol that is to be caught in the stream.

ignore(): The member function ignore() has two arguments, maximum number of characters to avoid and the termination character. For example,

 

cin.ignore (1,‘#’);

 

The statement ignores character 1 till character ‘#’is found.

 

Explanation: In the above program, the cin.get() function continuously reads characters through the keyboard till the user presses F6. The cout statement inside the loop displays the contents of variable c on the console. The cin.peek() statement checks the variable c. If the variable c contains ‘#’, it is ignored from the stream and not displayed on the screen.

putback() : The putback() replaces the given character into the input stream. For example,

cin.putback (‘*’);

where cin is an object and ‘*’ is the symbol which is replaced in the stream.

 

Explanation: In the above program, the cin.get() function continuously reads characters through the keyboard till the user presses F6. The cout statement inside the loop displays the contents of the variable c on the console. The if statement checks the contents of the variable c. If variable c contains a small letter ‘s’, the putback() statement sends capital ‘S’ in the stream. The small ‘s’ is replaced with capital ‘S’. The contents displayed will be with capital ‘S’.

Gcount(): This function returns the number of unformatted characters extracted from the input stream. The last statement should be get(), getline(), or read().

 

Explanation: In the above program, the getline() function reads text through the keyboard. The gcount() function returns the number of characters extracted from stream to variable len. It also counts the null character. The cout statement displays the value of variable len on the screen.

 

Explanation: In the above program, the cin.get() function reads data through the keyboard using first while loop. The if condition checks for blank space in the entered text. If space is found, the putback() statement replaces space dot (.). The putback() sends the given character in the input stream. The peek() also checks the ‘#’ symbol in the entered text, if it is found, the ignore() statement ignores the character and the character will not be displayed on the screen. The program is terminated when the key F6 or ctrl+z is pressed.

3.10  FORMATTED CONSOLE I/O OPERATIONS

C++ provides various formatted console I/O functions for formatting the output. They are of three types.

1. Ios class function and flags
2. Manipulators
3. User-defined output functions

The ios grants operations common to both input and output. The classes (istream, ostream, and iostream) derived from ios are special I/O with high-level formatting operations: The iostream class is automatically loaded in the program by the compiler. Figure 3.4 describes the hierarchy of stream classes.

1. istream performs formatted input.
2. ostream performs formatted output.
3. iostream performs formatted input and output.

streambuf allows an abstraction for connecting to a physical device. Classes derived from it work with files, memory, etc. The ios communicates to a streambuf. It keeps information on the state of the streambuf (good, bad, eof, etc.) and saves flags for use by istream and ostream.

• The streambuf class controls the buffer and its related member functions. It allows the ability to fill, flush, and empty the buffer.
• The streambuf is an object of ios class. The base class of input and output stream classes is ios class.
• The istream and ostream classes are derived classes of ios class and control input and output streams.
• The iostream class is a derived class of istream and ostream. It provides input and output functions to control console operations.

Table 3.4 describes the functions of ios class in brief.

 

Table 3.4 ios Class Function

Function	Working
width()	To set the required field width. The output will be displayed in given width.
precision()	To set number of decimal point to a float value.
fill()	To set a character to fill in the blank space of a field.
setf()	To set various flags for formatting output.
unsetf()	To remove the flag setting.

1. ios::width (member functions)

   The width() function can be declared in two ways.

   1. int width();
   2. int width (int);

   int width();

   If this function is declared as given above, it returns the present width setting.

   int width (int);

   If this function is declared as given above, it sets the width as per the given integer and returns the previous width setting. The setting should be reset for each input or output value if a width other than the default is desired.

    

   3.30 Write a program to set column width and display the characters at specified position.

   #include<iostream.h>

   #include<conio.h>

   int main()

   {

   clrscr();

   cout . width(5);

   cout<<“A”;

   cout . width(15);

   cout<<“B”;

   return 0;

   }

   OUTPUT

   A B

   Explanation: The first cout. width() statement sets the width 5. The cout statement sets the column width position at 5 and the cout statement displays the character “A” at column 5. Similarly, the column width is set 15 and the character ‘B’ is displayed at column 15.

    

   3.31 Write a program to use both the formats of width() function and display the result.

   #include<iostream.h>

   #include<conio.h>

   int main()

   {

   clrscr();

   cout.width(50);

   int x=cout.width(1);

   cout<<x;

   return 0;

   }

   OUTPUT

   50

   Explanation: In the above program, the width() function call sets the width at column 50. The second width() function call sets the width at column 1 and returns the previous setting, that is 50. The integer x collects this value. The cout() statement displays the number 50 at column 1.

2. ios::precision

   This function can be declared in two ways.

   1. int precision (int);
   2. int precision();

   int precision (int);

   If the function is declared as given above, it sets the floating-point precision and returns the previous setting. The precision should be reset for every value being output if we want a precision result other than the default.

   int precision();

   If the function is used as given above, it returns the current setting of floating-point precision.

    

   3.32 Write a program to set precision to two and display the float number

   #include<iostream.h>

   #include<conio.h>

   int main()

   {

   clrscr();

   cout.precision(2);

   cout<<3.1452;

   return 0;

   }

   OUTPUT

   3.14

   Explanation: In the above program, the cout.precision() statement sets float point precision to 2. The cout statement displays 3.14 instead of 3.1452.

    

   3.33 Write a program to set number of precision points. Display the results of 22/7 in different precision settings.

   #include<iostream.h>

   #include<conio.h>

   int main()

   {

   clrscr();

   int x=0;

   float pi;

   for (x=10;x>=1;x--)

   {

   pi=(float)22/7;

   cout.precision(x);

   cout<<“ ”<<pi;

   }

   x=cout.precision(1);

   cout<<“ Previous Setting :”<<x;

   return 0;

   }

   OUTPUT

   3.1428570747

   3.142857075

   3.14285707

   3.1428571

   3.142857

   3.14286

   3.1429

   3.143

   3.14

   3.1

   Previous Setting : 1

   Explanation: In the above program, the for loop executes from 10 to 1 in reverse order. Each time the equation 22/7 is calculated and the result is stored in the variable pi. The precision is set according to the value of variable x. The output of the program is as given above.

3. ios::fill

   This function can be declared in two ways.

   1. char fill();
   2. char fill (char);

   char fill();

   If the function is used as given above, it returns the current setting of fill character.

   char fill (char);

   If the function is used as given above, it resets the fill character and returns the previous setting.

    

   3.34 Write a program to fill empty spaces in a line with a specific symbol (*).      

   #include<iostream.h>

   #include<conio.h>

   int main()

   {

   clrscr();

   cout.fill(‘*’);

   cout.width(10);

   cout<<“H”;

   return 0;

   }

   OUTPUT

   *********H

   Explanation: In the above program, the statement cout.fill (‘*’); fills the blank spaces with * symbols. The cout. width() sets the width to 10 and the character ‘H’ is displayed at column 10. The column 1 to 9 remains blank. The symbol ‘*’ is displayed instead of blank spaces. This effect is due to cout.fill() statement as shown below.

   

   3.35 Write a program to fill blank spaces with different symbols.

   #include<iostream.h>

   #include<conio.h>

   int main()

   {

   clrscr();

   cout.fill(‘/’);

   cout.width(20);

   cout<<“WEL”<<endl;

   cout.fill(‘-’);

   cout.width(10);

   cout<<“DONE”;

   return 0;

   }

   OUTPUT

   /////////////////WEL

   ------DONE

   Explanation: This program is similar to the last one. Here, two different characters are used to fill the blank spaces in the specified width. The width is specified using cout.width() statement. The output can be observed as follows.

   
   TIP

   The character ‘’ (back slash) is not allowed in cout.fill() statement to fill the blanks. This is because it is used with escape sequences.

   3.36 Write a program to show the effect cout.fill().

   #include<iostream.h>

   #include<conio.h>

   int main()

   {

   clrscr();

   cout<<“Begin :”;

   cout.width(15);

   cout<<“ABC”;

   cout<<“ ”;

   cout<<“Begin :”;

   cout.width(15);

   cout.fill(‘#’);

   cout<<“ABC”;

   return 0;

   }

   OUTPUT

   Begin :        ABC

   Begin : ############ABC

   Explanation: The first line displays ABC following blank spaces because the fill(); is not used. In the second statement, the symbol ‘#’ is displayed because the fill character is set to ‘#’.

   

   3.37 Write a program to fill the unused filled area with ‘*’

   #include<iostream.h>

   #include<conio.h>

   int main()

   {

   clrscr();

   int x=0,j=0;

   float pi;

   cout.fill(‘*’);

   for (x=10;x>=1;x--)

   {

   pi=(float)22/7;

   cout.width(j++);

   cout.precision(x);

   cout<<“ ”<<pi;

   }

   cout.width(j++);

   cout.precision(x);

   cout<<“ ”<<pi;

   x=cout.fill();

   cout<<“ Fill setting :”<<(char)x;

   return 0;

   }

   OUTPUT

   3.1428570747

   3.142857075*

   3.14285707**

   3.1428571***

   3.142857****

   3.14286*****

   3.1429******

   3.143*******

   3.14********

   3.1*********

   3.142857

   Fill setting :*

   Explanation: In the above program, the precision setting and display of floating point number using precision is the same as in the previous example. In the for loop, each time width() is set to the value of variable j. The value of j increases at each iteration. The floating precision number decreases from top to bottom, and blank spaces remain in the specified field area by the statement width(). The unused area is filled with ‘*’. The setting of fill character is done before the for loop statement. The fill character may be set to any character. The fill() statement after for loop body displays the character used for filling.

4. ios::setf

   This function can be declared in two ways.

   1. long setf (long sb, long f);
   2. long setf (long);

   long setf (long sb, long f);

   The bits according to those marked in variable f are removed in the data member x_flags, and then reset to be those marked in variable sb. Using the constants in the formatting flag enumeration of class ios can specify the value of variable sb.

    

   long setf (long);

    

   If the above declaration is used in the program, it sets the flags according to those marked in the given long. The flags are set in the data member x_flags of class ios. Using the constants in the formatting flags can specify the long enumeration of class ios. It returns the previous settings.

3.11  BIT FIELDS

The ios class contains the setf() member function. The flag indicates the format design. The syntax of the unsetf() function is used to clear the flags. The syntaxes of the function are as follows.

 

Syntax: cout.setf (v1, v2);

Syntax: cout.unsetf(v1);

 

where variable v1 and v2 are two flags. Table 3.5 describes the flag, and bit-field setting can be used with this function. The unsetf() accepts setting of v1 and v2 arguments.

 

Table 3.5 Flags and Bits

Format	Flag (V1)	Bit Field (V2)
Left justification	ios::left	ios:adjustfield
Right justification	ios::right	ios:adjustfield
Padding after sign and base	ios::internal	ios:adjustfield
Scientific notation Fixed point notation	ios:: scientific ios:: fixed	ios::floatfield ios::floatfield
Decimal base Octal base Hexadecimal base	ios:: dec ios::oct ios::hex	ios::basefield ios::basefield ios::basefield

1. ios::adjustfield

   It is a data member and used with setf() function to arrange padding to the left or right, or for internal fill. It can be declared as follows.

   static const long adjustfield;

2. ios::floatfield

   It is a data member and used with setf() function to set the float point notation to scientific or fixed. It is declared as follows.

   static const long floatfield;

3. ios::basefield

   It is a data member and used with setf() function and used with setf() function to set the notation to a decimal, octal, or hexadecimal base. It is declared as follows.

   static const long basefield;

Explanation: In the above program, the fill character is set to sign “=”. The setf() is set to right justified. The column width is set to 20. The message “Figure” appears at the 20th column. Before the message the blank space is filled with the sign “=”. Again the justification property is set to left in setf() function. The text appears left justified. The output can be observed as follows.

Explanation: In the above program, the fill character is set to sign “=”. The setf() properties are set to internal and scientific. The scientific properties display the number in scientific (e) format. The internal properties display the sign before blank spaces. If the setting were removed, the output would be as given below.

Effect of statement

cout.setf (ios::internal, ios::adjustfield);

The output without this statement would be as follows.

The property ios::fixed displays the float number without scientific format, though the number is big. If the floating-point number is more than 6, then the extras are ignored. This format displays floating point up to 6 only.

 

Explanation: In the above program, the properties of setf() function are set to ios::hex, ios:: oct, and ios::dec. After this setting, the decimal number given in cout() statement will convert to its hexadecimal and octal equivalent, respectively. The hexadecimal number 0xfe is converted to its decimal equivalent.

3.12  FLAGS WITHOUT BIT FIELDS

The flags described in Table 3.6 have no corresponding bit fields. The programs on these functions are illustrated as follows.

 

Table 3.6 Flags without Bit Fields

Flag	Working
ios :: showbase	Uses base indicator on output
ios :: showpos	Displays + preceding positive number
ios :: showpoint	Shows trailing decimal point and zeros
ios :: uppercase	Uses capital case for hex output
ios :: skipws	Skips white space on input
ios :: unitbuf	Flushes all streams after insertion
ios :: stdio	Flushes stdout and stderr later insertion
ios :: uppercase	Uses capital characters for scientific and hexadecimal values
Ios::stdio	Adjusts the stream with C standard input and output
Ios::boolalpha	Converts Boolean values to text (“true” or “false”)

 

Explanation: In the above program, the setting ios::showpos displays the + sign before the number 1254. The setting ios::showpoint displays the trailing zeros after the number 1254.524. The setting ios::hex converts the decimal number to hexadecimal. It uses small letters. The setting ios::uppercase displays the hexadecimal number in uppercase.

3.13  MANIPULATORS

The output formats can be controlled using manipulators. The header file iomanip.h has a set of functions. The effect of these manipulators is similar to ios class member functions. Every ios member function has two formats. The first format is used for setting and the second format is used to understand the previous setting. But the manipulator does not return the previous setting. The manipulator can be used with cout() statement as follows.

cout<<m1 <<m2 <<v1;

Here, m1 and m2 are two manipulators and v1 is any valid C++ variable.

Table 3.7 describes the most useful manipulators. The manipulators hex, dec, oct, ws, endl, and flush are defined in iostream.h. The manipulators setbase, width(), fill(), etc., that require an argument are defined in iomanip.h.

 

Table 3.7 Pre-defined Manipulators

Manipulator	Function
setw (int n)	The field width is fixed to n
setbase	Sets the base of the number system
setprecision(int p)	The precision point is fixed to p
setfill (char f)	The fill character is set to the character stored in variable f
setiosglags(long l)	Format flag is set to l
resetiosflags(long l)	Removes the flags indicated by l
endl	Splits a new line
skipws	Omits white space on input
noskipws	Does not omit white space on input
ends	Adds null character to close an output string
flush	Flushes the buffer stream
lock	Locks the file associated with the file handle
ws	Omits the leading white spaces present before the first field
hex, oct, dec	Displays the number in hexadecimal, octal, and decimal format

 

Explanation: In the above program, the manipulator setw (10) sets the field width to 10. The message “hello” is displayed at 10th column. The endl inserts a new line. In the second cout() statement, the setprecision (2) manipulator sets the decimal point to 2. The number 2.5555 will be displayed as 2.56 at column 15. The manipulator setiosflag sets the hexadecimal setting for the display of number. The last cout() statement displays the equivalent hexadecimal of 84, that is, 54.

 

Explanation: In the above program, the integer variable x is declared and initialized with 84. The first cout statement displays the decimal number to its equivalent hexadecimal number. The manipulator hex converts a decimal number to its hexadecimal equivalent. The second cout statement converts a decimal number to its equivalent octal number.

 

Explanation: In the above program, the cin statement reads a number in hex format. The cout statement displays its equivalent decimal number with the use of dec manipulator.

 

Explanation: In the above program, endl manipulator is used to split the line. The two strings are displayed on two separate lines.

 

Explanation: In the above program, the statement flush (cout) flushes the buffer. This statement can be used as cout<<flush. For more information on buffer, read Section 3.4.

3.14  USER-DEFINED MANIPULATORS

The programmer can also define his or her own manipulator according to the requirement of the program. The syntax for defining manipulator is as follows.

 

The m_name is the name of the manipulator.

 

Explanation: Figure 3.7 illustrates the working of the program.

Fig. 3.7 Working of tab manipulator

In the above program, tab named manipulator is defined. The definition of tab manipulator contains the escape sequence ‘ ’. Whenever we call the tab manipulator, the ‘ ’ is executed and we get the effect of tab.

 

Explanation: In the above program, two manipulators N and P are created. When called, N displays the message “Negative number” and P displays the message “Positive number”.

3.15  MANIPULATOR WITH ONE PARAMETER

The prototype declared in the iomanip.h as described earlier allows us to define individual set of macros. The manipulator can be created without the use of int or long argument.

 

Explanation: In the above program, middle is a user-defined parameterized manipulator. It receives a value strlen (m), that is, string length. The header file IOMANIO.H defines a macro, OMANIO (int). It is expanded to class_OMANIP_int. Due to this, the definition consists of a constructor and an overloaded ostream insertion operator. When middle() function is added into the stream, it invokes the constructor which generates and returns an OMANIP_int object. The fc() function is called by the object constructor.

3.16  MANIPULATORS WITH MULTIPLE PARAMETERS

In this type of manipulators, multiple arguments are passed to the manipulator. The following program explains it.

 

Explanation: The above program is similar to the previous one. The only difference is that here two parameters are used. The user-defined manipulator is assigned two integer values. The first argument decides the number of spaces and the second argument decides the number of decimal places. After initializing the w_p structure, the constructor is called. The constructor creates and returns a _OMANIP object. The output of the program is shown above.

3.17  MORE PROGRAMS

Explanation: In the above program, integer variables p_amount, period, i_rate, interest, and t_amount are declared. The principal amount, period in years, and rate of interest are read through the keyboard using respective variable with cin statement. The interest is calculated by the statement interest=(p_amount*period*i_rate)/100 and the interest calculated is assigned to variable interest. The total amount is calculated by adding interest in the principle amount.

 

Explanation: In the above program, the cout.width(7) statement sets width to 7. The cout statement displays the five digits. The total number of digits are less than the total width. Hence, two blank spaces are displayed at the beginning as shown below.

Explanation: The output of the program can be understood from the following table.

The showpos flag displays the positive sign at the beginning. The showpoint option displays decimal point and trailing zeros. The internal and adjustfield flags add blank spaces between the sign and the number.

 

Explanation: In the above program, the integer variable k is initialized to 0 and long double variables n and f are initialized to 1.00. The precision is set to 0. The setf() function sets the precision to fixed position. The statement cout.width (15) fixes the field width. Thus, using while loop repetitive operations are performed. The output of the program is given above.

 

Explanation: In the above program the variable num is initialized to 1.5. The while loop is executed repetitively and square and cube of the number are calculated using the pow() function. The functions cout.width() and cout.precision() set the field width and the number of floating points. The output of the program is shown above.

 

Explanation: In the above program, ios base fields such as oct, hex, and dec are set using setf() function. After this setting the decimal number given in cout() before printing is converted to the above formats. The while loop repetitively performs this task and the result is displayed as above.

 

Explanation: In the above program, rs and arg are two user-defined manipulators. The arg manipulator contains various member functions of ios class that are used to manage the screen.

 

Explanation: The operator << and variable j together are assigned to macro d and the format string %d is assigned to macro i. Both are used in cout and printf statements, respectively.

 

Explanation: By default, the cout statement omits the trailing decimal zeros. The trailing zeros can be displayed using a setting as shown in the above program. The result of the above program is shown as follows in tabular format for the sake of understanding.

Explanation: In the above program, an array item[3][3] is declared and initialized with float numbers. The following formatting statements are used.

 

cout.precision(2) – Sets decimal point limit to two digits.

cout.fill(‘*’) – Fills ‘*’ in blank space of field.

cout.width(8) – Sets field width to 8.

 

The first and second for loops are used to read and display the contents of the array on the screen. The output of the program is as follows.

Here, each field has width 8. The numbers are displayed with right justification. The blank spaces are filled with ‘*’ symbol.

1. The input/output function of C++ works with different physical devices. It also acts as an interface between the user and the device.
2. A stream is a series of bytes and acts as source and destination for data. The source stream is called as input stream and the destination stream is called as output stream.
3. The cin, cout, cerr, and clog are pre-defined streams.
4. The header file iostream.h files must be #include when we use cin and cout functions.
5. The istream and ostream are derived class from ios base class. Figure 3.4 displays all the derived classes.
6. The formatting of output can be effectively done with member function of ios class. The member function width(), precision(), fill(), and setf() allows the user to design and display the output in formatted form.
7. Table 3.6 describes the list of functions without bit fields. These functions are also used for formatting the output
8. The putback() replaces the given character into the input stream. The member function ignore ignores the number of given character till it finds the termination character.
9. Manipulators also help the user in formatting the output. The programmer can also create his or her manipulators.
10. The header file iomanip.h contains pre-defined manipulators. Table 3.7 describes these manipulators.

(A) Answer the following questions

1. List the names of pre-defined streams with their ‘C’ equivalents?
2. What are formatted and unformatted I/O functions?
3. Distinguish between
   1. cin() and scanf()
   2. cout() and printf()
   3. ios::fixed and cout.precision()
4. What are the uses of put() and get() functions?
5. What is the use of getline() function? Which two arguments does it require?
6. Describe the bit fields required in setf() function.
7. List the flags without bit fields with their working.
8. What is the role of iostream.h and iomanip.h header files?
9. Write the statement for concatenation of two strings using cout.write() statement.
10. Describe the procedure for designing manipulator.
11. What is the function of peek() and ignore() functions?
12. What are single and multiple parameter manipulators?
13. In which format does the out statement display the address of a variable? How can it be converted to unsigned?
14. In which situation is the putback() function useful?
15. What is the use of ignore() function?
16. What do you mean by formatted and unformatted data?

(B) Answer the following by selecting the appropriate option

1. The cin and cout functions require the header file to include
   1. iostream.h
   2. stdio.h
   3. iomanop.h
   4. none of the above
2. The set.precision() is used to set
   1. number of digits
   2. decimal places
   3. field width
   4. none of the above
3. To fill unused sections of the field, the character is set by the function
   1. fill()
   2. width()
   3. precision()
   4. none of the above
4. The manipulator <<endl is equivalent to
   1. ‘ ’
   2. ‘ ’
   3. ‘’
   4. none of the above
5. This function accepts the string with blank spaces
   1. cin
   2. scanf()
   3. getline();
   4. none of the above
6. The streams is a
   1. flow of integers
   2. flow of data
   3. flow of statements
   4. none of the above
7. The statement cout<<hex<<15; gives the data in
   1. hexadecimal format
   2. octal format
   3. binary format
   4. decimal format
8. The gcount() function counts the
   1. inserted character
   2. unformatted extracted character
   3. both (a) and (b)
   4. none of the above
9. The buffer is used to move data between
   1. input and output devices
   2. i/O devices and computer
   3. input devices to storage devices
   4. none of the above
10. The buffer is a
    1. block of memory
    2. part of ram
    3. part of hard disk
    4. none of the above

(C) Attempt the following programs

1. Write a program to read five float numbers with six decimal places.
2. Write a program to display the hexadecimal and octal equivalent of 85, 25, 152, 251, and 458 numbers.
3. Write a program to display decimal equivalent of hexadecimal numbers 0x52, 0x98, 0x101, 0x524, and 0x421.
4. Write a program to read ten records of a student with the information Name, Age, and Date of Birth. Arrange the information (output) in the following format. Fill the unused field with dots.

   

5. Write a program to accept string using get()function. Display the string using write()and put()function. Mention the difference between write()and put()functions.
6. Write a program to design the following manipulators.

   Manipulator Name	Function (Escape Sequence)
   <<bkp (backspace)	‘’ or ‘ ’
   <<newl	‘ ’
   <<bell	‘a’
   <<plus	‘+’ (displays + sign)
   <<dollar	$ (displays $ sign)

7. Write a program to read item code, quantity, and price and calculate the amount. Display the data in the following format.

   Note:

   1. Sr.no. and Item code are left justified.
   2. The price and amount are right justified.
   3. Three-digit precision for amount field.
   
8. Write a program to enter text up to 100 characters through the keyboard. Ignore? symbol and replace it with *. Display dot between two words.
9. Given x = 5, y = 8, and z = 12, what will be the value of the variables on the left side of the following equations?
   1. a = x/y * z
   2. b = y/z * x
   3. c = z * y/z
   4. d = x * z/y
   5. d = (x/y) * z
10. If p = 0.5, q = −2.0, r = 7.3, s = 10.4, m = 2, n = −3, what will be the value of the variables on the left side of the following equations.
    1. x = 5.0 * p + q – (r + s*3.0)
    2. y = 3.0 * p + q + s*2
    3. z = p * s + q*r – s * q/5.0
    4. a = sqrt(4.0 – r + 9.0 * q)
11. Solve the following algebraic equations.
    1. k = 4.5 log₁₀ x + 2xy + x⁵
    2. j = (bx + x)/ (bx – b)
    3. z = (x)2 + (x + 1)2 + (x + 2)2
    4. u = a * b/(c + d * g + k) + e
12. Write a program to generate the following outputs.

    

13. Write a program to generate the following output.

    

(D) What will be the output of the following programs?

1. cout.setf(ios::left, ios::adjustfield);

   cout.fill(‘*’);

   cout.precision(2);

   cout.width(7);

   cout<<345.54;

   cout.width(8);

   cout<<78;

2. cout.setf(ios::internal, ios::adjustfield);

   cout.fill(‘$’);

   cout.precision(4);

   cout.width(11);

   cout<<-543.453;

3. cout.setf(ios::showpos);

   cout.setf(ios::showpoint);

   cout.setf(ios::internal, ios::adjustfield);

   cout.precision(4);

   cout.width(12);

   cout<<2342.34;

4. cout.precision(2);

   cout<<4.57<<endl;

   cout<<7.1453<<endl;

   cout<<4.5132<<endl;

   cout<<8.004<<endl;

5. cout.fill(‘$’);

   cout.precision(4);

   cout.setf(ios::internal, ios::adjustfield);

   cout.setf(ios::scientific, ios::floatfield);

   cout.width(13);

   cout<<-78.47854;

6. cout.fill(‘=’);

   cout.setf(ios::internal, ios::adjustfield);

   cout.setf(ios::scientific, ios::floatfield);

   cout.unsetf(ios::scientific);

   cout.width(15);

   cout<<- 3.121;

7. cout.width (7);

   cout<<123<56;

(E) Additional programs

1. Program to read integer, character, float, and double integer and display them.

   #include<iostream.h>

   #include<conio.h>

   int main()

   {

   clrscr();

   int a=10;

   float b=10.4;

   char c=‘b’;

   double d=12345.4567;

   cout<<“ Value of a is :”<<a;

   cout<<“ Value of b is :”<<b;

   cout<<“ Character assigned to c is :”<<c;

   cout<<“ The double value d is: :”<<d;

   return(0);

   }

   OUTPUT

   Value of a is :10

   Value of b is :10.4

   Character assigned to c is :b

   The double value d is: :12345.4567

2. Program to use different formats of typecasting and display the converted values.

   #include<iostream.h>

   #include<conio.h>

   int main()

   {

   clrscr();

   int a=97;

   float b=100.4;

   char c=‘z’;

   double d=12345.4567;

   cout<<“ Integer in character format is :”<<char(a);

   cout<<“ Float in integer format is:”<<int(b);

   cout<<“ Character in integer format is :”<<int(c);

   cout<<“ Double in integer format is :”<<int(d);

   return(0);

   }

   OUTPUT

   Integer in character format is :a

   Float in integer format is :100

   Character in integer format is :122

   Double in integer format is :12345

3. Program to display HAI! using, C++ using the put() statement.

   #include<iostream.h>

   #include<conio.h>

   int main()

   {

   clrscr();

   cout.put(‘H’).

   put(‘A’).put(‘I’).put(‘!’);

   cout<<endl;

   cout.put(‘C’).put(‘+’).put(‘+’);

   return(0);

   }

   OUTPUT

   HAI!
   C++

4. Program to display lower- and uppercase characters from a to z.

   #include<iostream.h>

   #include<conio.h>

   #include<stdio.h>

   int main()

   {

   clrscr();

   int j;

   cout<<“Lowercase characters:”;

   for(j=122;j>96;j--)

   cout<<(char)j<<“ ”;

   cout<<endl;

   cout<<“Uppercase characters:”;

   for(j=90;j>64;j--)

   printf(“% c”,j);

   return (0);

   }

   OUTPUT

   Lowercase characters: z y x w v u t s r q p o n m l k j i h g f e d c b a

   Uppercase characters: Z Y X W V U T S R Q P O N M L K J I H G F E D C B A

5. Program to read characters using a sequence of get() statements and display the characters read using a sequence of put() statements.

   #include<iostream.h>

   #include<conio.h>

   int main()

   {

   clrscr();

   int age;

   float num;

   char sex;

   char*msg=“ C++ is an object oriented language”;

   sex=‘F’;

   age=25;

   num=1004.5;

   cout<<“Sex:”<<sex<<endl;

   cout<<“Age:”<<age<<endl;

   cout<<“Entered float number is:”<<num<<endl;

   cout<<“Message entered is:”<<msg<<endl;

   cout<<10<<“ ”<<20<<“ ”<<30<<endl;

   cout<<“Modified float number is:”;
   cout<<num+5;

   return(0);

   }

   OUTPUT

   Sex:F

   Age:25

   Entered float number is:1004.5

   Message entered is: C++ is an object oriented language

   10 20 30

   Modified float number is:1009.5

6. Program to display the addresses of variables in hex and unsigned integer format.

   #include<iostream.h>

   #include<conio.h>

   int main()

   {

   clrscr();

   int a=77,c=78;

   float b=5.1252;

   cout<<“Address of a=”<<&a<<endl;

   cout<<“Address of b=”<<&b<<endl;

   cout<<“Address of c=”<<(unsigned)&c<<endl;

   return(0);

   }

   OUTPUT

   Address of a=0x8f69fff4

   Address of b=0x8f69ffee

   Address of c=65522

7. Program to read characters using read() and display it by write() function.

   #include<iostream.h>

   #include<conio.h>

   int main()

   {

   clrscr();

   char name[6];

   cout<<“ Enter a string:”;

   cin.read(name,5);

   cout<<endl;

   cout<<“Entered string is:”;

   cout.write(name,5);

   return(0);

   }

   OUTPUT

   Enter a string:Amit

   Entered string is:Amit

8. Program to read a string using getline() function and display it using write() statement.

   #include<iostream.h>

   #include<conio.h>

   #include<string.h>

   int main()

   {

   char a[7];

   clrscr();

   cout<<“ Enter any string:”;

   cin.getline(a,7);

   cout<<“ Entered string:”<<a;

   cout<<“ Entered string:”;

   cout.write(a,7);

   cout<<“ Entered string;”;

   cout.write(a,strlen(a));

   return(0);

   }

   OUTPUT

   Enter any string:Mumbai

   Entered string: Mumbai

   Entered string: Mumbai

   Entered string: Mumbai

9. Program to generate the following output.

   C

   C+

   C++

   C++e

   C++ea

   C++eas

   C++easy

   C++easy

   C++easy

   #include<iostream.h>

   #include<conio.h>

   #include<string.h>

   int main()

   {

   clrscr();

   char p,b[8];

   cout<<“ Enter any string:”;

   cin.getline(b,8);

   cout<<“ Entered string:”;

   for(p=0;p<=strlen(b);p++)

   {

   cout.write(b,p);

   cout<<“ ”;

   }

   for(p=8;p>=strlen(b);p--)

   {

   cout.write(b,p);

   cout<<“ ”;

   }

   return(0);

   }

   OUTPUT

   Enter any string:C++easy

   Entered string:

   C

   C+

   C++

   C++e

   C++ea

   C++eas

   C++easy

   C++easy

   C++easy

10. Program to generate the following output.

    Decimal.................64

    Hexadecimal..........40

    Octal......................100

    #include<iostream.h>

    #include<conio.h>

    #include<iomanip.h>

    int main()

    {

    clrscr();

    int a=64;

    cout<<setfill(‘.’);

    cout<<setiosflags(ios::left);

    cout<<setw(16)<<“Decimal”;

    cout<<resetiosflags(ios::left);

    cout<<setw(6)<<dec<<a<< endl;

    cout<<setiosflags(ios::left);

    cout<<setw(15)<<“Hexadecimal”;

    cout<<resetiosflags(ios::left);

    cout<<setw(6)<<hex<<a<<endl;

    cout<<setiosflags(ios::left);

    cout<<setw (15)<<“Octal”;

    cout<<resetiosflags(ios::left);

    cout<<setw(6)<<oct<<a<<endl;

    return(0);

    }

    OUTPUT

    Decimal..................64

    Hexadecimal..........40

    Octal.......................100

11. Program to generate the following output.

    c

    c+

    c++

    c++e

    c++ea

    c++eas

    c++easy

    c++easy

    c++eas

    c++ea

    c++e

    c++

    c+

    c

    #include<iostream.h>

    #include<conio.h>

    #include<string.h>

    int main()

    {

    clrscr();

    char p,b[9];

    cout<<“ Enter any string”;

    cin.getline(b,9);

    cout<<“ Entered

    string:”;

    for(p=0;p<=strlen(b);p++)

    {

          cout.write(b,p);

          cout<<“ ”;

    }

    for(p=strlen(b);p>=0;p--)

    {

          cout.write(b,p);

          cout<<“ ”;
          } 

          return(0); 

    }

    OUTPUT

    Enter any stringc++easy

    Entered string:

    c

    c+

    c++

    c++e

    c++ea

    c++eas

    c++easy

    c++easy

    c++eas

    c++ea

    c++e

    c++

    c+

    c

12. Program to generate output using flag bits such as showpos, showpoint, hex, and uppercase of given number.

    #include<iostream.h>

    #include<conio.h>

    int main()

    {

    clrscr();

    cout.setf(ios::showpos);

    cout<<1254;

    cout.setf(ios::showpoint);

    cout<<“ ”<<1254.524;

    cout.setf(ios::hex,ios::basefield);

    cout<<“ ”<<184;

    cout.setf(ios::uppercase);

    cout<<“ ”<<184;

    return(0);

    }

    }

    OUTPUT

    +1254

    +1234.524000

    b8

    B8

13. Program to fill the trailing digits of number by ‘$’ symbol.

    #include<iostream.h>

    #include<conio.h>

    int main()

    {

    clrscr();

    int s=0,j=0;

    float pi;

    cout.fill(‘$’);

    for(s=4;s>=1;s--)

    {

       pi=(float)22/7;

          cout.width(j++);

          cout.precision(s);

          cout<<“ ”<<pi;

    }

    cout.width(j++);

    cout.precision(s);

    cout<<“ ”<<pi;

    s=cout.fill();

    cout<<“ previous setting :”<<(char)s;

    return(0);

    }

    OUTPUT

    3.1429

    3.143$

    3.14$$

    3.1$$$

    3.142857

    previous setting :

14. Program to print “*******ABC*******”.

    #include<iostream.h>

    #include<conio.h>

    int main()

    {

    clrscr();

    cout.fill(‘*’);

    cout.width(10);

    cout<<“ABC”;

    cout.fill(‘*’);

    cout.width(7);

    cout<<“*”;

    return(0);

    }

    OUTPUT

    *******ABC*******

15. Program to use different formats of width() and display the results.

    #include<iostream.h>

    #include<conio.h>

    int main()

    {

    clrscr();

    cout.width(20);

    int x=cout.width(20);

    cout<<x;

    return(0);

    }

    OUTPUT

    20

16. Program to use skipws and stdio flags.

    #include<iostream.h>

    #include<conio.h>

    int main()

    {

    clrscr();

    char x[5];

    cout<<“Enter array of characters:”;

    cin>>x;

    cout.setf(ios::skipws);

    cout<<“Entered array of characters:”<<x;

    cin>>x;

    cout.setf(ios::skipws);

    cout<<“ Entered array of characters:”<<x;

    cin>>x;

    cout.setf(ios::stdio);

    cout<<“ Entered array of characters:”<<x;

    return(0);

    }

    OUTPUT

    Enter array of characters: as h ok

    Entered array of characters: as

    Entered array of characters: h

    Entered array of characters: ok

17. Program to convert decimal to hexadecimal and octal number.

    #include<iostream.h>

    #include<conio.h>

    #include<iomanip.h>

    int main()

    {

    clrscr();

    int a;

    cout<<“Enter the number :”;

    cin>>a;

    cout<<“ Hexadecimal number :”<<hex<<a;

    cout<<“ Octal number:”<<oct<<a;

    return(0);

    }

    OUTPUT

    Enter the number : 156

    Hexadecimal number : 9c

    Octal number : 234

18. Program for converting hexadecimal number to decimal number.

    #include<iostream.h>

    #include<conio.h>

    #include<iomanip.h>

    int main()

    {

    clrscr();

    int a;

    cout<<“ Enter hexadecimal number:”;

    cin>>hex>>a;

    cout<<“ Equivalent decimal number is:”<<dec<<a;

    return(0);

    }

    OUTPUT

    Enter hexadecimal number is : f

    Equivalent decimal number is : 15

19. Program to convert octal number to hexadecimal and decimal number.

    #include<iostream.h>

    #include<conio.h>

    #include<iomanip.h>

    int main()

    {

    clrscr();

    int a;

    cout<<“ Enter octal number :”;

    cin>>oct>>a;

    cout<<“ Equivalent hexadecimal number is:”<<hex<<a;

    cout<<“ Equivalent decimal number is :”<<dec<<a;

    return(0);

    }

    OUTPUT

    Enter octal number : 124

    Equivalent hexadecimal number is : 54

    Equivalent decimal number is : 84

20. Program to generate the following output.

    ****1000.2

    *100.45

    #include<iostream.h>

    #include<conio.h>

    int main()

    {

    clrscr();

    cout.fill(‘*’);

    cout.precision(3);

    cout.width(10);

    cout<<1000.2<<endl;

    cout.fill(‘*’);

    cout.precision(2);

    cout.width(7);

    cout<<100.4532;

    return(0);

    }

    OUTPUT

    ****1000.2

    *100.45