C++ INTERACTIVE INPUT AND OUTPUT
Input
The extraction operator >> is used for general input of variable values.
The extraction operator is defined for all the built-in basic C++ types. It
is possible to input values for multiple variables in the same statement by
chaining them together with the extraction operator. For each occurrence
of >> you must supply the name of the variable where you want the input
value assigned (a statement can’t end with >>).
cin >> value1 >> value2; is the same as cin >> value1;
cin >> value2;
Rules for how C++ reads different types of values:
int Skip any leading spaces or blank lines, read digits until encountering a
character that is not valid in an integer value, like a blank space or a
special character, or a decimal point, or a letter, or the end of the line
(result of pressing Enter)
double Skip any leading spaces or blank lines, read digits until encountering a
character that is not valid in a floating-point value, like a blank space
or a special character other than a decimal point, or a letter, or the end
of the line.
char Skip any leading spaces or blank lines and read the first non-blank
character encountered.
string Skip any leading spaces or blank lines and read characters
until encountering a blank space or the end of the line.
When you’re reading from the keyboard, you should precede your input
statements with output statements explaining what it is that your program
is expecting the user of the program to enter – these are called prompting
messages. Otherwise, the cursor will be blinking on the output screen, but
the user of the program has no way of knowing what the program is waiting
for.
Prompting messages should be brief because people tend not to read instructions
very well. Sometimes it helps to give the user an example of the input the
program expects rather than to try and write out a long detailed description.
Some knowledge about the anticipated users of your program may give you
an idea of the amount of detail that would be necessary or desirable in your
instructions.
You can input the values your program needs in any order you want and in
any combination you want (one at a time, two at a time, etc.). I strongly
recommend reading only one value at a time because it greatly simplifies
the instructions and possibly helps to prevent errors by the user while keying
the input values. If you expect the user to enter multiple values without
additional instructions in between values, then you probably need to explain
about the spacing required. If you’re only asking for one value at a time,
spacing isn’t a problem.
// Monty Python
// Program 1
// CSCI 151 Height Conversion Program
1
