Sams Teach Yourself C++ in 21 Days

Working with Streams 603

17

Int: 2

Long: 30303

Double: 393939397834

Float: 3.33

Word: Hello

Unsigned: 85

Int: 2

Long: 30303

Double: 3.93939e+011

Float: 3.33

Word: Hello

Unsigned: 85

Int, Long, Double, Float, Word, Unsigned: 3 304938 393847473 6.66 bye -2

Int: 3

Long: 304938

Double: 3.93847e+008

Float: 6.66

Word: bye

Unsigned: 4294967294

Again, several variables are created, this time including a chararray. The user is

prompted for input and the output is faithfully printed.

On line 34, the user is prompted for all the input at once, and then each “word” of input

is assigned to the appropriate variable. It is to facilitate this kind of multiple assignment

that cinmust consider each word in the input to be the full input for each variable. If cin

was to consider the entire input to be part of one variable’s input, this kind of concate-

nated input would be impossible.

Note that on line 42, the last object requested was an unsignedinteger, but the user

entered -2. Because cinbelieves it is writing to an unsignedinteger, the bit pattern of -2

was evaluated as an unsignedinteger, and when written out by cout, the value

4294967294 was displayed. The unsignedvalue 4294967294 has the exact bit pattern of

the signedvalue -2.

Later today, you will see how to enter an entire string into a buffer, including multiple

words. For now, the question arises, “How does the extraction operator manage this trick

of concatenation?”

The cinReturn Value ....................................................................................

The return value of cinis a reference to an istreamobject. Because cinitself is an

istreamobject, the return value of one extraction operation can be the input to the next

extraction.

OUTPUT

ANALYSIS