IO stream manipulation

We can format and manipulate the input output streams using IO manipulators. We can display blank spaces between fields , we can display numbers in hexadecimal or octal, we can even display boolean values as true and false instead of 1 and 0.

Here are the IO manipulators defined in <iostream>

boolalpha noboolalpha - display boolean values as true and false
showbase noshowbase - add prefix of 0x and 0 to hexadecimal and octal values
showpoint noshowpoint - display decimal point always for floating point numbers
showpos noshowpos - display + sign for non-negative numbers
skipws noskipws - skip whitespace for input using cin stream
uppercase nouppercase - display uppercase characters with hex or boolean values
unitbuf nounitbuf - flush the buffer after each operation or not
hex dec oct - display the integers using hexadecimal or decimal or octal
left right internal - set placement for fill characters
fixed scientific - display the floating value as fixed point or scientific notation
ws - used with input stream to consume white spaces
ends - add end of stream ('\0') to the output stream and flush it
endl - add end of line character to the output stream and flush
flush - flush the output stream

The next set of manipulators are defined in <iomanip>

setbase - sets the base for integers - can be 10,16 or 8
setfill - sets the fill charcter. Default is " "
setprecision - sets the precision for floating point values
setiosflags - set multiple ios flags
resetiosflags - reset ios flags
setw - set the width for the next input/ouput field.

Let us look at some examples
   int a=20;
   cout<<hex<<a<<endl;//output is 14
   a = 10;
   cout<<hex<<uppercase<<a<<endl;//output is A
   out<<oct<<a<<endl;//output is 12
   cout<<hex<<showbase<<a<<endl;//output is 0xa

   float b=12.0;
   cout<<b<<endl;//output is 12
   cout<<showpoint<<b<<endl;//output is 12.0

   b = 12.346789;
   cout<<setprecision(5)<<b<<endl;//output is 12.347

   cout<<scientific<<b<<endl;//output is 1.23468e+1
   cout<<showpos<<a;//output is +10

get(), put() and getline() functions

istream class has two more functions to read other than extraction operator. These are get() and getline().

get() function can be used to read one character from input stream.
   char ch;
   cin.get(ch);

getline(char *,int len, [char delimiter]) can be used to read a string which contains whitespaces. Extraction operator terminates reading when it encounters whitespace. If there is a need to read complete line, we can use readline() function.

   char arr[40];
   cin.getline(arr,40);//read a string terminated by newline character
   char arr2[200];
   cin.getline(arr2,200,'#');//reads a string terminated by # character

Let us look at another program which reads characters from keyboard and display them on screen until # is pressed

char ch;
do {
cin.get(ch);
   cout.put(ch);
}
while(ch!='#');