1. Basic Input and Output
C++ programs can read and write information using streams
A simple input stream accepts typed data from a keyboard
A simple output stream writes data to the terminal

2. Standard Input/Output Streams
A stream is a sequence of characters
Streams convert internal representations to character streams or vice versa
>> input (extraction) operator
<< output (insertion) operator
Any character (printable or not)
A stream has no fixed size

3. cin – input stream Defined in the iostream library cin
// first.cpp #include <iostream> // for stream IO #include <string> using namespace std; int main() // start of main function { string name; // Get the name cin >> name; // Output the distance in miles. cout << "Hello " << name << endl; return 0; }
Defined in the iostream library
#include <iostream>
cin
Standard input stream
Accepts typed input from the keyboard
Uses the extraction operator >>
Extraction operator
Load input into a variable
cin >> name;
“points” in the direction of the data flow!

4. cout – output stream Defined in the iostream library cout
// first.cpp
#include <iostream> // for stream IO
#include <string>
using namespace std;
int main() // start of main function {
string name;
// Get the name
cin >> name;
// Output the distance in miles.
cout << "Hello " << name << endl;
return 0; }
Defined in the iostream library
#include <iostream>
cout
Standard output stream
Outputs to the terminal window
Uses the insertion operator <<
Insertion operator
Output to a device (or file)
cout << "Hello " << name << endl;
“points” in the direction of the data flow!

5. Input Stream, >> Operator
Last character read is tracked with an input stream buffer pointer
Each new input attempt begins at current pointer position
Leading white space (blanks, tab, newline) skipped until first non- white-space character is located, then…
For strings, characters are read into string variable until white space is encountered
For numeric data, characters are read into the variable until a character is encountered that is not a valid character for that data type

6. Input Stream Example
$ John
$ 2.3 $
User types this
note: $ is the prompt
loads buffer…
Stream Buffer
Pointer J o h n
space 2 3 6 . 1 \n 4 5 7 8 9 10 11 12 13 14 15 16
User starts typing, Stream Buffer is loaded until:
“Enter” is typed (‘\n’), at position 12:
Pointer starts at 1, “John” gets stored in name - stops at 5
Pointer skips over space in 5, 23 gets stored in i - stops at 8
Pointer skips 8, 6.1 gets stored in x - stops at 12
More typing, buffer loads until “Enter” is typed again (16)
Pointer skips over 12, 2 gets stored in j - stops at 14
… because an int (j) cannot contain a decimal point!
Pointer continues from 14, .3 gets stored in y - stops at 16
string name;
int i, j;
float x, y;
cin >> name;
cin >> i >> x >> j >> y;

7. getline() getline(stream, string_variable);
An alternate way to get input
Syntax:
getline(stream, string_variable);
Reads from a “stream” (like cin)
Loads everything from the current pointer location up to the next delimiter into a string variable
Default delimiter is ‘\n’ (end of line)
Does NOT skip leading whitespace!!!
// string variable
string name;
// read an entire
// line into “name”
getline(cin, name);

8. Output Stream By default, cout outputs data with no formatting Strings
It just outputs the characters required to represent the variable
Strings
Output the characters in the string
Integers
Output the digits in the number
Float point numbers
Can vary based on the value, usually a minimal representation of the number
Boolean
By default : 0 for false, 1 for true

9. Formatting output Embed spaces between items
Add a “carriage return” to start a new line
Use “endl” to output a c/r
Same as outputting the character ‘\n’
cout << “George” << “ “ << “Washington” << endl;
Or use manipulators

10. Manipulators Provide greater control over output formatting
Embed them in the output stream
cout << fixed << setw(10) << setprecision(3) << x << endl;
Settings persist until changed
Must include the iomanip library
#include <iomanip>
setw is an exception
Width resets after a value is output

11. Output Stream - Manipulators
setw
Set the width of the next output value. After output the value resets to zero. Zero width defaults to the object width (i.e. no padding)
boolalpha
noboolalpha
Switches between textual and numeric representation of booleans
showpoint
noshowpoint
Controls whether decimal point is always included in floating-point representation
skipws
noskipws
Controls whether leading whitespace is skipped on input
left
right
Sets the placement of fill characters (i.e. right or left justification)
fixed
scientific
Changes formatting used for floating-point I/O
endl
Outputs '\n' and flushes the output stream
setprecision
Changes floating-point precision
Manipulators require the inclusion of the iomanip library
#include <iomanip>