CSCI 152 C++ INTERACTIVE INPUT AND OUTPUT
Output
The insertion operator << is used for general output of values of multiple types. It has been defined to
output values in a default format for all of the built-in basic C++ types.
Because of the way the operator is defined, it is possible to output multiple values in the same statement by
chaining them together with the << (insertion) operator:
cout << value1 << value2; is the same as cout << value1; cout << value2;
where the variables (or constants or expressions) may be of any of the built-n basic types.
The insertion operator converts values to text form. By default, values are displayed in a width equal to their
size and formatted as follows:
char A type char value, if it represents a printable character, is displayed as a character in a field
one character wide.
int Numeric integer types are displayed as decimal integers in a field just wide enough to hold the
number and, if the value is negative, a minus sign.
float Floating-point types are displayed with 6 places to the right of the decimal, except that
trailing fractional zeros aren't displayed. If there are no significant digits to the right of the
decimal point, printing of the decimal point is suppressed along with the trailing zeros.
The number may be displayed in E-notation, depending upon the value of the number (which
depends on the implementation being used). Again, the field is just wide enough to hold the
number and, for a negative value, a minus sign.
string Strings are displayed in a field width equal in width to the length of the string.
Examples of default field widths (these defaults may vary from one compiler to another):
1 #include <iostream>
2 using namespace std;
3 int main ()
{ // value displayed:
4 cout << '*' << "NCC 1701" << "*\n"; // *NCC 1701*
5 char ch = 'K'; int t = 273;
6 cout << '*' << ch << "*\n"; // *K*
7 cout << '*' << t << "*\n"; // *273*
8 cout << '*' << -t << "*\n"; // *-273*
9 double f1 = 1.200;
10 cout << '*' << f1 << "*\n"; // *1.2*
11 cout << '*' << (f1 + 1.0 / 9.0) << "*\n"; // *1.311111*
12 double f2 = 1.6E7;
13 cout << '*' << f2 << "*\n"; // *16000000*
14 cout << '*' << (f2 + 1.0 / 9.0) << "*\n"; // *16000000.111111*
15 cout << '*' << (f2 + 2.0e5) << "*\n"; // *1.62e+07*
16 float f3 = 2.3e-4;
17 cout << '*' << f3 << "*\n"; // *0.00023*
18 cout << '*' << f3 / 10 << "*\n"; // *2.3e-05*
// The point where the default switches from fixed to scientific is dependent
// on the compiler you use.
19 float f4 = 5.0;
20 cout << '*' << f4 << "*\n"; // *5*
21 return 0;
}
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