| Initial Comments |
/* Formatting and <iomanip.h>
file: 4ex2.cpp (or used as 4ex2.appended)
FALL 1998
___________________________________
Jacob Y. Kazakia jyk0
September 28, 1998
Programming example 2 of week 4
Recitation Instructor: J.Y.Kazakia
Recitation Section 01
___________________________________
Purpose: This program reads three numbers a, b, and c through
the keyboard and outputs them on the screen in various
SCIENTIFIC formats.
Algorithm: The functions: setiosflags, setw, setprecision are
used to format output.
ios:: fixed
ios:: scientific
ios:: showpoint
*/
#include <iostream.h>
#include <iomanip.h>
void main()
{
// variables are typed and defined
float a,b,c; // the three numbers
cout<<" \n\n Please enter 3 numbers \n a = ";
cin>>a;
cout<<"\n b = ";
cin>>b;
cout<<"\n c = ";
cin>>c;
|
Since the function setiosflags is sent to cout,
Data directed to the default output will be in scientific form |
// Output everything in scientific form
cout<<setiosflags( ios::scientific );
//***********************************************************
|
Precision is set to 5 digits after the decimal point.
A string of numbers is sent out so that we can easily examine the location
of data in the output.
The width is set to 20 for each one of the three numbers a, b, and c. |
cout<<"\n\n\n With precision 5 and width 20 \n";
cout<<setprecision(5);
cout<<"\n 1 2 3 4 5 \n";
cout<<"12345678901234567890123456789012345678901234567890 \n" ;
cout<< setw(20)<<a <<setw(20)<< b <<setw(20)<< c ;
//***********************************************************
|
Precision is set to 3 digits after the decimal point.
A string of numbers is sent out so that we can easily examine the location
of data in the output.
The width is set to 10 for each one of the three numbers a, b, and c. |
cout<<"\n\n\n With precision 3 and width 10 \n" ;
cout<<setprecision(3);
cout<<"\n 1 2 3 4 5 \n";
cout<<"12345678901234567890123456789012345678901234567890 \n" ;
cout<< setw(10)<<a <<setw(10)<< b <<setw(10)<< c ;
//***********************************************************
|
| |
cout<<endl<<endl;
cout<<" enter e (exit) to terminate the program....";
char w;
cin>>w;
}
/* THESE ARE SOME OF THE OUTPUTS
|
|
The first number, when entered as fixed, needs 14 decimal digits.
However the number of significant digits is 1, so comes out correctly
in scientific format.
Suppose we had precision 15. Do you think that we could have captured
the detail at the end of number c?
Notice that 5 digits after the decimal point are shown even if they are
zero.
The numbers are placed into the 20 slot openings with right justification.
|
Please enter 3 numbers
a = 0.0000000000001
b = 123456789.45678
c = -4567.0000000045
With precision 5 and width 20
1 2 3 4 5
12345678901234567890123456789012345678901234567890
1.00000e-13 1.23457e+08 -4.56700e+03
|
Note that the third number needs 10 places to be displayed.
One for sign
One for integer part
One for point
Three for precision
Four for exponent
RULE:
Width >= precision + 7
What do you think would happen if we violated this rule? Try it out. |
With precision 3 and width 10
1 2 3 4 5
12345678901234567890123456789012345678901234567890
1.000e-13 1.235e+08-4.567e+03
enter e (exit) to terminate the program....
************************************************************
|
Same story here for a different set of numbers.
Try to understand why the output looks as it does. |
************************************************************
Please enter 3 numbers
a = 123
b = 12
c = 0.6789
With precision 5 and width 20
1 2 3 4 5
12345678901234567890123456789012345678901234567890
1.23000e+02 1.20000e+01 6.78900e-01
With precision 3 and width 10
1 2 3 4 5
12345678901234567890123456789012345678901234567890
1.230e+02 1.200e+01 6.789e-01
enter e (exit) to terminate the program....e */
|
© 2001 J.Y. Kazakia. All rights reserved