1. IO Overview
CSCE 121
Strongly influenced by slides created by Bjarne Stroustrup and Jennifer Welch

2. cin & cout Standard in Standard out Standard error
Where input comes into a program by default
Normally the keyboard
Can be modified (e.g. pipes in UNIX)
Standard out
Where output is sent
Normally the screen
Can be modified (e.g. pipes)
Standard error
Where error messages are sent
Frequently set to a file
cin
cout
cerr
clog
Standard in
Standard out
Standard err
buffered error
Keyboard
Monitor
Default: Same as cout
Default: Same as cerr
Apparently, clog is the same as cerr, just buffered.
Example:
$ ./prgm [ARGS] 0<IN 1>OUT 2>ERR

3. Input and Output (IO or I/O)
Program
Output

4. Input and Output (IO or I/O)
data source:
input library
input device
device driver
our program
data destination:
output library
device driver
output device

5. The Stream Model An ostream Values of various types
‘c’
“somewhere”
ostream
1.234
Values of various types
123
buffer
An ostream
turns values of various types into character sequences
sends those characters somewhere (console, file, main memory, another computer…)

6. The Stream Model An istream Values of various types
‘c’
“somewhere”
istream
1.234
Values of various types
123
buffer
An istream
gets characters from somewhere (console, file, main memory, another computer,…)
turns character sequences into values of various types

7. The Stream Model Supports reading and writing of typed entities
<< (output) and >> (input/extraction) plus other operations
type-safe
formatted
typically stored as text
but not necessarily, e.g, binary streams
extensible
define your own I/O operations for your own types
a stream can be attached to any I/O or storage device

8. Many different Streams
What applies to cout/cin will also apply to
file streams
string streams
Etc.

9. Model