Formatting Output

Formatting Output • Escape Sequences • iomanip.h Objects • setw() • setiosflags(…) • setprecision()

Output ¾ coutThe object cout is used to direct data to the ststandard output device, usually the monitor. • w predefined stream objectw in iostream libraryw used with insertion operator << *

Output ¾ coutSyntax: cout << ExprOrString; • Read << as “put to”. cout << 24; cout << ‘y’; cout << “Hello”; • Note: none of these contain a “\n” or endl, and thus may not be displayed immediately. *

Output ¾ coutSyntax: cout << ExprOrString; • cout << “The answer to question “;cout << q_num; cout << “ is “;cout << 1.5 * pay_rate; • cout << endl; // force a new line and flush q_num 5 pay_rate 6 The answer to question 5 is 9.0 *

space Output ¾ coutSyntax: cout << ExprOrString << ExprOrString;Each appends data to the stream. • cout << “Num1 * num2 is “ << num1*num2; • OUTPUTNum1 * num2 is 110 * *

no space Output ¾ coutSyntax: cout << ExprOrString << ExprOrString;Each appends data to the stream. • cout << “Num =“ << 35.1; • OUTPUTNum =35.1 * *

space no space Spaces – Essential for StringsSyntax: cout << ExprOrString << ExprOrString;Each appends data to the stream. • OUTPUT Hi, Shadowhow are you? cout << “Hi, “ << name << “how are you?”; * * *

no ; cout << “The answer to question “ << qu_num << “ is “<< 1.5 * pay_rate; Output ¾ coutSyntax: cout << ExprOrString << ExprOrString; • cout << “The answer to question “;cout << q_num;cout << “ is “;cout << 1.5 * pay_rate; align the put-to operators for good style * *

no ; cout << “The answer to question number 17 “ << “is listed after question “ << lastqu << ‘.’; More Multi-line SyntaxSyntax: cout << ExprOrString << ExprOrString << ExprOrString ; • cout << “The answer to question number 17 is listed after question “;cout << lastqu << ‘.’; Strings should never span multiple lines error * *

Escape Sequences • \ Changes the meaning of the character that follows it.\n hard return\t tab\\\\”“\a beep or bell • These must be within quotation marks.

\n \n gives a blank line Escape Sequences • cout << “Name\tTotal\tGrade\n”;cout << “Miyo\t186\t B\n”;cout << “\n Jake\t211\t A\n”;cout << “Syd\t203\t A\n”; • OUTPUT Name Total Grade Miyo 186 B Jake 211 A Syd 203 A_ *

Escape Sequences • \ Changes the meaning of the character that follows it.\” take quotes literally “James \”Big Jim\” Traficant” gives James “Big Jim” Traficant *

Escape Sequences “\n Alfonsus\n\”Butch\” \nBillone” gives Alfonsus“Butch”Billone “|\n Alfonsus\n\t\”Butch\” \tBillone|” gives | Alfonsus “Butch” Billone| * * * *

Formatting Output • does the same thing as \n - inserts a hard return • requires the insertion operator cout << endl << endl; is the same as:cout << “\n\n”; endl

2.3 Numerical Output using cout • Using cout to output the results of an arithmetic expression • Numerical output should be displayed attractively • Programs are often judged on the presentation of their output, (in addition to the accuracy of the results) • For example, $1.897 is not acceptable output

cout Syntax • cout << ExprOrStringOrManipulator << ExprOrStringOrManipulator...; • For Example: • cout << setw(5) << 350; uses field width of 5 • cout << setw(7) << 350; uses field width of 7

Formatting Output • the iomanip header file contains objects which have special effects on the iostream. #include <iostream>#include <iomanip> *

Formatting Outputiomanip contains the objects which havespecial effects on the iostream.…… …... • setw(n) how many columns for data setprecision(n) sets number of decimals • setiosflags(ios::fixed) displays 6 digits after the decimal * * *

¨o33¨7132¨oHi 337132¨Hi fields expand Formatting Outputsetw(n) how many columns for data • cout << setw(4) << ans cout << setw(1) << ans << setw(5) << num << setw(3) << num << setw(4) << “Hi”; << setw(3) << “Hi”; * *

x = format result314.0 setw(10) setprecision(2) ¨ooo314.00 point counts 314.0 setw(7) setprecision(5) 314.00000 columns added Formatting Outputsetprecision(n) sets number of decimals • 314.0 setw(10) setprecision(5) ¨314.00000 * * *

Formatting Outputsetiosflags(ios::fixed) displays 6 digits after the decimal • #include<iostream> • #include<iomanip> • using namespace std; • void main() • { • double v = 0.00123456789; • double w = 1.23456789; • double x = 12.3456789; • double y = 1234.56789; • double z = 12345.6789;

Formatting Output • cout <<v<< endl<<w<< endl <<x<< endl • <<y<< endl <<z<<”\n\n”; • cout << setiosflags(ios::fixed); • cout <<v<< endl <<w<< endl <<x<< endl • <<y<< endl <<z<<”\n\n”; • cout << setprecision(2); • cout <<v<< endl <<w<< endl <<x<< endl • <<y<< endl <<z<<”\n\n”; • }

Formatting Output • default • 0.00123457 • 1.23457 • 12.3457 • 1234.57 • 12345.7 ios::fixed 0.001235 1.234568 12.345679 1234.567890 12345.678900 + setprecision(2) 0.00 1.23 12.35 1234.57 12345.68

output 6 18 124 --- 149 Numerical output with cout • An example from the 2nd Edition text: • #include <iostream> • using namespace std; • int main() • { • cout << 6 << ‘\n’ • << 18 << ‘\n’ • << 124 << ‘\n’ • << “---\n” • << 6+19+124 << ‘\n’; • return 0; • }

output 6 18 124 --- 149 Numerical output with cout • Same example using setw( ): • #include <iostream> • #include <iomanip> • using namespace std; • int main() • { • cout << setw(3) << 6 << ‘\n’ • << setw(3) << 18 << ‘\n’ • << setw(3) << 124 << ‘\n’ • << “---\n” • << 6+19+124 << ‘\n’; • return 0; • }

Formatting Output • For decimal alignment use: • ios::fixed and setprecision( ) • setw( ) use setw( ) each time cout << setiosflags(ios::fixed) << setprecision(n); l l l cout << “- -” << setw(n) << var1 << setw(n) << “- -”; cout << “- -\t” << setw(n) << var1 << setw(n) <<var2; *

Common Programming Errors, cout and Variables • Forgetting to declare all variables • Storing wrong data type into a variable • Forgetting to initialize variables • Dividing integer values incorrectly • Mixing data types without knowing effect • Forgetting insertion symbol <<

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Formatting Output