Lecture #5:iostream functions

واإلخراج اإلدخال دوال

Dr. Hmood Al-DossariKing Saud University

Department of Computer Science

4 March 2012

Overview Input Functions ( اإلدخال (دوال

cin.get(); cin.ignore(); cin.putback(); cin.peek(); cin.clear();

Output Functions ( اإلخراج (دوال setprecision(); fixed showpoint setfill setw(); left/right

• ‘>>’ will skip all leading whitespace characters.

• Consider the variable declarations:

char ch1, ch2;

int num;

• Suppose, the input is: A 25

• Consider the following statement:

cin>>ch1>>ch2>>num;

• Output: I. ‘A’ is stored in ch1,

II. ‘2’ is stored in ch2 and

III.5 is stored in num.

Note: the blank is skipped by the extraction operator ‘>>’,.

Input Functions: cin.get()

• Using get function with cin will take spaces into account.

• The syntax of cin statement with get function:

cin.get(varChar);

• In previous example:

cin.get(ch1);

cin.get(ch2);

cin>>num;

• Output: I.‘A’ is stored in ch1,

II.a blank is stored in ch2 and

III.25 is stored in num.

Input Functions: cin.get()

• Ignore function is used to discard a portion of the input.• The syntax of cin statement with ignore function:

cin.ignore(intExp, chExp);

• Example:char first, last;;first=cin.get();cin.ignore(256,' ');last=cin.get();cout<< "Your initials are :" << first << last<<"\n";

• Suppose, the input is: Hmood Al-Dossari

• Output:

Your initials are :HA

Input Functions: cin.ignore()

• putback function puts the character ch back to the input stream. Thus, the next extracted character will be ch.

• The syntax of cin statement with putback function:

istream.putback(varChar);istream.get(varChar);

Where, varChar is an input stream variable.

Input Functions: istream.putback()

• peek function reads and returns the next character without extracting it.

• The syntax of cin statement with peek function:variable = istream.peek();

Input Functions: istream.peek()

Input Functions: putback and peek

• When an input stream enters the fail state, the system ignores all further I/O stream. Thus, programmer can use the stream function clear to restore the input to a working state.

• The syntax of cin statement with peek function:cin.clear();

Example:

int a = 23;

int b = 34;

cin>>a>>b;

cin.clear();

cout<<a<<“ , "<<b;

Input Functions: cin.clear()

Suppose the input is: 12 ROutput: 12 , 34

Suppose the input is: 19 56Output: 19 , 56

• التالي البرنامج مخرجات أكتب

int a = 23;

int b = 34;

cin>>a>>b;

cin.clear();

cout<<a<<“ , "<<b;

Activity 1 - 1نشاط -

Suppose the input is: R 12Output:

• setprecision function is used to control the output of floating-point numbers.

• a maximum of six decimal places for default output of floating-point.

• The syntax of setprecision:cout<<setprecision(n);

• This function requires #include<iomanip.h> header file.

Example:

float a = 2.3889;

cout<<Setprecision(3);

cout<<a;

Output Functions: setprecision()

Output:

2.38

• fixed sets the output of floating-point numbers in a fixed decimal format on the standard device.

• The syntax of fixed:cout<<fixed;

• Note: to disable the manipulator fixed function to default setting, you can use:

cout.unsetf(ios::fixed);

Example:

float a = 2.3889;

cout<<fixed;

cout<<a;

Output Functions: fixed

Output:

2.38890

• If the decimal part of a decimal number is zero, the output may not show the decimal point and the decimal part.

• showpoint function forces the output to show the decimal point and decimal part.

• The syntax of showpoint:cout<<showpoint;

Example:

float a = 2;

cout<<fixed;

cout<<showpoint;

cout<<a;

Output Functions: showpoint

Output:

2.00000

• setw is used to output the value of an expression in specific columns.

• The value of the expression can be either a string or a number.

• The syntax of setw:cout<<setw(n)<<“............”;

Example:

cout<<setw(12)<<“Hmood”;

Output Functions: setw()

1 2 3 4 5 6 7 8 9 10 11 12

domH o

• setfill is used to allow us to fill the unused columns with a character other than a space.

• The syntax of setfill:cout<<setfill(‘&’);

Example:

cout<<setfill’&’;

Output Functions: setfill()

1 2 3 4 5 6 7 8 9 10 11 12

domH o&&&&&& &

• left is used for left-justified.

• The syntax of left:cout<<left;

• We can disable left function by using the stream function unsetf.ostream.unsetf(ios::left);

Example:

cout<<left;

cout<<setw(12)<<“Hmood”;

Output Functions: left function

1 2 3 4 5 6 7 8 9 10 11 12

doomH

• right is used for right-justified.

• The syntax of right:cout<<right;

• We can disable right function by using the stream function unsetf.ostream.unsetf(ios::right);

Example:

cout<<right;

cout<<setw(12)<<“Hmood”;

Output Functions: right function

1 2 3 4 5 6 7 8 9 10 11 12

domH o

• التالي البرنامج مخرجات أكتب

cout<<

cout<<right;

cout<<setw(7)<<“Ali \n”;

Cout<<left;

Cout<<setw(11)<<“MMM”;

---------------------------------------

float a=7.334;

cout<<setprecision(3);

cout<<fixed;

cout<<“a=”<<a;

Activity 2 - 2نشاط -