I/o Systems & File Processing: By… Kharadi Fahad

I/O Systems & File Processing by… kharadi fahad

c++ stream classes IOS

istream

get() getline() read() ----------------

Overload ‘<<’

iostream

ostream

put() write() --------------

Overload ‘>>’

Types of i/o operation I/O OPERATION

UNFORMATTED

put() , get() getline() , write() ----------------------------------------------------------------------

Overload Overload oper. oper. ‘<<’ ‘<<’ ,, ‘>>’ ‘>>’

FORMATTED

IOS CLASS FUNCTION

USER DEFINED OUTPUT FUNCTION

Width(),precision() ,fill(),setf() ,unsetf()

MANIPULATORS

setw(),setprecision(), setfill(),setioflags() ,resetioflags()

unformatted 1>get():eg:# include void main() { char c; cin.get(c); while(c!='\n') { cout<
• 2>put() :# include void main() { char c; cin.get(c); while(c!='\n') { cin,put(c); cin.get(c); } }

3>getline():Syntax:

cin.getline(line,size);

#include #include void main() { clrscr(); int size=20; char c[20]; cout<<"enter the line-->" ; cin>>c; cout<<"city name-->"<"; cin.getline(c,size); cout<"; cin.getline(c,size); cout<<"the entered line is-->"<
Output 1 enter the line-->hellooops city name-->hellooops enter the new line--> enter again the new line-->hello fahad the entered line is-->hello fahad

Output 2 enter the line-->hello oops city name-->hello enter the new line--> oops enter again the new line-->hello fahad the entered line is-->hello fahad

4>write():Syntax:

cin.write(line,size);

#include

#include void main() { clrscr(); char c[20]; cout<<“enter the line”; cin.getline(c,20); cout<<“the entered line is”; cout.write(c,20); getch(); }

Output  enter the line-->hello oops the entered line is-->hello oops

formatted IOS CLASS FUNCTION

MANIPULATORS

width(int w)

setw(int w)

precision(int d)

setprecision(int d)

fill(char c)

setfill(char c)

setf(arg1,arg2)

setioflags(arg1,arg2)

unsetf()

resetioflags()

All above are used with cout.____

IOS CLASS FUNCTION • 1>width(int w):Eg1:cout.width(6); cout<<361; cout.width(5); cout<<18; OUTPUT:3 6 1

Eg2:cout.width(6); cout<<361; cout<<18; OUTPUT:1 8

3 6 1 1 8

2> precision(int d);Eg:cout.precision(4); cout<<sqrt(2)<<‘\n’; cout<<3.14159<<‘\n’; cout<<2.50003<<‘\n’; OUTPUT:1.4112TRUCATED VALUE. 3.1416ROUNDED TO NEAREST VALUE. 2.5 NO TRAILING ZEROS

• 3> fill(char c):Eg:cout.fill(‘ * ‘); cout.width(10); cout<<1265; OUTPUT:-

* * * * * *

1 2 6 5

4>Formattingflags,Bit fields:setf(arg1,arg2):Format arg1 Left-justified o/p ios::left Right-justified o/p ios::right Padding after base or ios::internal sign indicator

arg2 ios::adjustfield ios:: adjustfield ios:: adjustfield

Scientific notation ios::scientific Fixed point notation ios::fixed Decimal base ios::dec Octal base ios::oct Hexadecimal base ios::hex

ios::floatfield ios:: floatfield ios::basefield ios:: basefield ios:: basefield

Eg:cout.fill(‘*’); cout.setf(ios::left,ios::adj ustfield); cout.width(12); cout<<“oops”<<‘\n’; OUTPUT:o o p s

* * * * * * * *

• To display following 341.32 3 4 1 29.00

19.230

1

9

3

2

2

9

2

3

Other arg1

Description

setf(ios::showpoint)

display a trailing decimal point and trailing decimal zeros when real numbers are displayed

setf(ios::showpos)

display a + character with positive values.

setf(ios::showbase)

to display the numeric base of integral values. With hexadecimal values the 0x prefix is used, with octal values the prefix 0.

setf(ios::uppercase)

use capital letters in the representation of (hexadecimal or scientifically formatted) values

setf(ios::skipws)

leading white space characters (blanks, tabs, newlines, etc.) are skipped

setf(ios::unitbuf)

flush the stream after each output operation.

setf(ios::stdio)

flush the standard C streams stdout and stderr after each output operation.

Eg:cout.setf(ios::showpos);; cout.setf(ios::showpoint); cout.precision(4); cout.setf(ios::fixed,ios::floatfield); cout.setf(ios::internal,ios::adjustfield); cout.width(10); cout<<120.3<<’\n’; OUTPUT:-

+

1 2 0 .

3 0 0 0

User defined manipulator Syntax: ostream & manipulator(ostream & output) { ----------------return output; }

Eg:ostream & oops(ostream & output) { output<<“oops!!!!”; return output; } main() { cout<<“hello”<