Input and Output Streams in 9.1 C++.

Meaning of input and output

1) Input data from keyboard and output to display screen.
2) Input and output to external files (discs).
3) Use the space specified in memory for input and output. String Input Output

Standard Output Stream

C++ Input and Output Streams

Common stream classes in I/O class libraries

Class name	Effect	header file
ios	Abstract Base Class	iostream
istream	Universal Input Stream	iostream
ostream	Universal Output Stream	iostream
iostream	Universal input-output stream	iostream
ifstream	Input File Stream	fstream
ofstream	Output File Stream	fstream
fstram	Input and Output File Stream	fstream
istrstream	Input String Stream Class	strstream
ostrstream	Output String Stream Class	strstream
strstream	Input Output String Stream Class	strstream

4 stream objects defined in iostream header file

object	Meaning	Corresponding device
cin	Standard input stream	keyboard
cout	Standard Output Stream	screen
cerr	Standard error stream	screen
clog	Standard error stream	screen

Format output of standard type data

1. Use Controller to Control Output Format
These controllers are defined in the header file iomanip, which needs to be declared at the beginning.
Binary: dec (ten), hex (sixteen), oct (eight)

int b = 123456;
cout<<hex<<b;

Read more P50

2. Use member functions of stream objects to control output format
More See P410

Output characters with stream member function put

A member function put designed to output a single character

cout.put('a');
cout.put(97);//The character a is also output because ASCII codes are supported

put functions can be called continuously in a statement

cout.put(71).put(79).put(79).put(68).put('\n');
display GOOD Back line break

Standard input stream

cin stream

Judgement status: normal - cin value is true (non-zero value)

if(!cin)
	cout<<"error";

Stream member function for character input

1. Read a character using the get function
No parameters

int c;
cout<<"Enter a number:"<<endl;
c = cin.get();
getchar()and cin.get()Same function

Has parameters (used to determine whether the read was successful)

int ch;
if(!cin.get(ch))
	cout<<"File End!"<<endl;

There are three parameters (n-1 characters read from input stream)

cin.get(Character Array,Number of characters n,Termination Character)
cin.get(Character Pointer,Number of characters n,Termination Character)

2. Read a line of characters with getline (n-1 characters, plus'\0'for n characters in the character array)

cin.getline(Character Array(Character Pointer),Number of characters n,Termination Character)

Other member functions

1. eof function (judge end of file)

while(!cin.eof())
Reach the end true, otherwise 0

2. peek function (observe next character)

c = cin.peek();

3. putback function

cin.putback(ch);

4. ignore function

cin.ignore(n,Termination Character);
cin.ignore(5,'A');

I/O operations for 9.2 files

Opening and Closing of Files

1. Open Disk File
(1) Call member function open of file stream

ofstream outfile;//Define object outfile
outfile.open("C:\new\f1.dat",ios::out);//Open file as output

(2) Specify parameters when defining stream objects

ofstream outfile("C:\new\f1.dat",ios::out);

File Input and Output Settings (see P422 for details)

mode	Effect
ios::in	Open file as input
ios::out	Open the file as output (default), empty it if it already has the same name
ios::app	Open file as output, write data added at end
ios::ate	Open an existing file with the file pointer pointing to the end of the file
ios::binary	Open the file binary (otherwise ASCII is defaulted)
ios::in|ios::out	Open file as input and output, readable and writable
ios::out|ios::binary	Open an output file in binary mode

2. Close disk files

ofstream outfile;//Define object outfile
outfile.close();

outfile can be associated with other files after closing, for example:

outfile.open("C:\new\f2.dat",ios::out);

File Read-Write Stream Operation, How to Copy Between Two Files

#include<fstream>
#include<iostream>

using namespace std;

int main(){
	
	char temp[20];
	
	fstream in,out;
	
	in.open("file1.txt",ios::in);
	out.open("file2.txt",ios::out);
	
	while(!in.eof()){
		in.getline(temp,20);
		cout<<temp<<endl;
		out<<temp<<endl;
	}
	
	 
	in.close();
	out.close();	
	
	return 0;
}