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Electrical and Computer Engineering 1of 12
UAH CPE 112
Simple Data Types: Built-In
and User-Defined
•Additional C++ operators: +=, -=, *=, /=
Statement Equivalent Statement
i += 5; i = i + 5;
pivotPoint *= n + 3; pivotPoint * (n + 3);
•The Cast Operation
Two forms:
intVar = (int)floatVar;
intVar = int(floatVar); (only works if the data type name is a
single identifier)
myVar = (unsigned int) someFloat; (the only way for this one)
Electrical and Computer Engineering 2of 12
UAH CPE 112
Working with Character Data
•Each computer uses a particular character set, two
in substantial use today are ASCII and EBCDIC.
The vast majority use ASCII.
•Character Issues:
–Comparing Characters: if (ch >= ‘a’ && ch <= ‘z’) –
islower is preferred usage
–Converting Digit Characters to Integers: ‘9’ –‘0’ = 9
–Converting to Lowercase and Uppercase: toupper and
tolower can help (#include <cctype>)
–Accessing Characters Within a String: Use position
number, e.g. ch = inputStr[2];
Electrical and Computer Engineering 3of 12
UAH CPE 112
More on Floating-Point Numbers
•Comparing Floating-Point Numbers: check for an
error within some range
•Underflow and Overflow: Numbers can be too
large or too small to be represented.
•Cancellation Error: problems can occur when
arithmetic operations occur on values of wildly
different magnitudes: (1 + 0.00001234 –1) =
0.00001234. For four digits of precision, this
doesn’t work, why?
Electrical and Computer Engineering 4of 12
UAH CPE 112
Practical Implications of
Limited Precision
•Limited precision has led to
–Mercury splashdown in unknown location, delaying the
recovery of the spacecraft and the astronaut.
–Specialized high-tension cables linking a hydroelectric
dam to the nearest power distribution point had to be
redone due to precision problems.
–A bank employee stole infinitesimal amounts from a
large number of accounts.
Electrical and Computer Engineering 5of 12
UAH CPE 112
User-Defined Simple Types
•Enumeration Types –C++ allows the user
to define a new simple type by listing
(enumerating) the literal values that make
up the domain of the type. These literal
values are identifiers, not numbers,
separated by commas.
•Example:
enum Days (SUN, MON, TUE, WED,
THU, FRI, SAT);
Electrical and Computer Engineering 6of 12
UAH CPE 112
Enumeration Type Declaration
•EnumDeclaration
enum Name {Enumerator, Enumerator, …};
•Enumerator
Identifier = ConstIntExpression
•Legal or Illegal?
enum Vowel {‘A’, ‘E’, ‘I’, ‘O’, ‘U’};
enum Places {1st, 2nd, 3rd};
enum Starch {CORN, RICE, POTATO, BEAN};
enum Grain {WHEAT, CORN, RYE, BARLEY, SORGHUM};
