cout / cin - University of Kentuckykwjoiner/cs215/notes/IntroCinC... · 2020. 8. 18. · cin >>...
Transcript of cout / cin - University of Kentuckykwjoiner/cs215/notes/IntroCinC... · 2020. 8. 18. · cin >>...
Introduction to
is used to print to the screen in a C++
Console Application.
is used to read user input from the
keyboard in a C++ Console Application.
and are defined by the C++
standard library . To use these
utilites:
#include <iostream>
Additional utilities for formatting are in:
#include <iomanip>
is a stream from the application
(executing in memory) to the screen.
Characters are inserted into the stream and
“fall out” on the screen.
I/O manipulations may be used to format
the characters before they are written.
is a stream from the application
(executing in memory) to the screen.
Characters are inserted into the stream and
“fall out” on the screen.
I/O manipulations may be used to format
the characters before they are written.
cout << expression;
where expression is a literal, variable or
more complex expression that evaluates to
one value.
cout << expr1 << expr2 << ...
<< exprn;
is equivalent to:
cout << expr1;
cout << expr2;
...
cout << exprn;
Can vary greatly depending on the situation.
Make it clear to another programmer and
easy to maintain.
Good style:
cout << ”+-------+\n”;
cout << ”| Hello |\n”;
cout << ”+-------+\n”;
Good style:
cout << ”+-------+\n”
<< ”| Hello |\n”
<< ”+-------+\n”;
Poor style:
cout << ”+-------+\n| Hello |\n+-------+\n”;
Floating Point Numbers:
// print floats/doubles in decimal format with
// 2 digits past the decimal point.
// Prints nothing. In effect until changed.
cout << fixed << setprecision(2);
Field Widths:
// set total field with of a value
cout << setw(10) << ”Hello”;
Prints 5 spaces then 5 characters:
Hello
Field Widths:
// effect is only for 1 value
cout << setw(10) << ”Hello” << ”There”;
Prints 5 spaces then 5 characters then There
HelloThere
Justification:
// effect is until Justification is changed
cout << left << setw(10) << ”Hello”;
cout << right << setw(10) << ”There”;
Prints 5 chars, 5 spaces, 5 spaces, 5 chars
Hello (10 spaces) There
is a stream from the keyboard to the
console application (executing in memory)
Characters are inserted into the stream by
the user and are extracted by
(simple)
cin >> variable;
in general
variable = whatever is entered by the user;
in general
- halts execution of the program
- the user enters data and presses ENTER
- the data is converted to the data type of the
variable.
- the data entered is stored in the variable
- execution continues
specifically
Exactly how behaves depends on the:
- data type of the variable
- what is currently in "the stream", if anything.
- data type of the data entered by the user
For now, assume that for each :
- the user enters the correct data type
- the user enters NO SPACES/TABS/etc
- the user presses ENTER when done