1. ENERGY 211 / CME 211
Lecture 9
October 10, 2008

2. Streams
To exchange data between memory and I/O devices or storage, use streams
cin, cout are examples of streams
Some member functions:
clear() resets stream to allow read/write
bad() returns true if stream in bad state
good() returns true if stream usable
eof() returns true if no input available
istream, ostream have useful subclasses for I/O with various sources

3. Console Streams Declared in <iostream> header
Predefined instances of class ostream write data to the screen
cout for standard output
cerr for reporting errors
clog for writing logging data
Predefined instance cin, of class istream, reads from the keyboard

4. File Streams Declared in <fstream> header
Use ofstream object to write to file named at construction
ifstream object allows reading from a file named at construction
Constructors want a const char *, so use c_str() member of string
Available functions/operators:
>>, <<, char get(), put(char), getline(istream, string), etc.

5. String Streams Declared in <sstream>
ostringstream object (derived from ostream) allows writing to a string, accessed with str() member function
istringstream object (derived from istream) allows reading from a string designated at construction
Usual functions/operators available
Useful for working with a line of input in memory instead of in another stream

6. Manipulators
The following belong to the std namespace, and are used with >>, << operators
endl outputs a newline and flushes output buffer
setw(int n) sets the field with for the next output to n
right, left set justification of output
dec, oct, hex set base for reading or writing integers

7. Persistence Data in program's memory goes away when execution ends
To make data persistent, write to file
Then, program can read from file to resume working with data
>>, << operators allow simple method of making data persistent
For more complex objects, requires agreed-on format to map text to object

8. structs
A struct is a primitive data structure that allows data of different types to be grouped into a single entity
Primarily used in C; in C++, superseded by classes, which offer much more functionality
A struct contains fields, or members, which are given any names and types
Fields are stored consecutively in memory, in order of declaration

9. structs, cont’d Form of declaration:
struct { type1 name1; type2 name2; … } varname;
To access fields, use the . operator:
structname.fieldname
To access field through pointer to struct, use arrow operator:
pointername->fieldname
To associate type name with struct:
typedef struct { … } typename;

10. Character functions Declared in <cctype> header
Useful for classifying or manipulating characters (and for Project 2!)
isalnum(c): true if c is letter or digit
isalpha(c): true if c is a letter
iscntrl(c): true if c is a control character
isdigit(c): true if c is a digit

11. More Character Functions
islower(c): true if c is uppercase
ispunct(c): true if c is punctuation
isspace(c): true if c is white space (space, tab or newline)
isupper(c): true if c is uppercase
tolower(c) converts c to lowercase
toupper(c) converts c to uppercase

12. Next Time
All about pointers!
Project 2 Questions