The Standard C++ Input/Output Commands

MELJUN CORTESMELJUN CORTES

The Console Output Library Command

There are several library commands used for output of data, but we’ll learn to use first the cout statement.

The syntax is: 

cout [<< format string] [<< argument list] Where:

– cout refers to the console output library command– << refers to the standard output stream operator (SOSO)– the format string can be an ordinary character, string, or an escape

character– the argument list can be a simple variable, constant, or an expression.

Example#include <iostream>

using namespace std; void main(void){

char ch;int i;float f;double d;

 // initialize variables

ch = 'Z';i = 70;f = 0.123456789;d = 0.123456789123456789;

 

Example (continued…)cout << "Hello\n"; // prints a stringcout << 'A' << "\n" ; // prints a char constant cout << ch << "\n"; // prints the value of a char variable cout << 567 << "\n"; // prints an integer constant

cout << i << "\n"; // prints the value of integer variable cout << 1.25 << "\n"; // prints a float constantcout << f << "\n"; // prints the value of float variablecout << 3.1416 << "\n"; // prints a double constant cout << d << "\n"; // prints a value of a double variable cout << "ch = " << ch << "\n"; // using different parameterscout << "i = " << i << " f = " << f << " d= " << d << "\n";

}

The Console Input Library Command

Like the output library commands, there are also several input library commands, but we’ll learn to use first the cin statement.

The syntax is:cin [>> argument list]

 Here, the argument list can only be variables, which

will hold the data input of the user through the use of the keyboard.

Example#include <iostream>

using namespace std;

void main(void)

{

char ch;

int i;

float f;

double d;

Example (continued…)cin >> ch; // expects a character input from usercin >> i; // expects an integer input from usercin >> f; // expects a float input from usercin >> d; // expects a double input from user

 // outputs the input valuescout << “ch = ” << ch;

cout << “ i = ” << i << “ f = ” << f ; cout << “ d = ” << d << “\n”;}

cin Examples with Prompts

#include <iostream>

using namespace std; void main(void){

char ch;int i;float f;double d;

 cout << "Input value of char variable ch: ";cin >> ch;

cin Examples with Prompts (continued…)

cout << "Input value of int variable i: ";cin >> i;cout << "Input value of float variable f: ";cin >> f;cout << "Input value of double variable d: ";cin >> d;

 // outputs the input values

cout << "ch = " << ch << " i = " << i; cout << " f = " << f << " d = " << d << "\n";}

Special Formatting Characters • The ‘\n’ character is just one of the special formatting

characters of C++, it is referred to as the new line character. • If used alone, the character must be enclosed in single quotes

or in double quotes. • It can also be used in conjunction with other characters in a

format string enclosed in double quotes. • There is, however, an alternative to the ‘\n’ character that is

more readable. • Users can use the endl in place of ‘\n’, read as end line. • But unlike the ‘\n’ character, endl can not be used as part of a

string, i.e enclosing it in double quotes – or even single quotes. • Doing so will cause unexpected results or a logical error.

Common Formatting Characters