Zimmer
CSCI 130
3/18/2016
CHAPTER 10 - Simple Data Types: Built- in and User – Defined
Additional C++ Operators –
Combined Assignment Operators:
+=, -=, *=, /=
Increment and Decrement Operators:
++, -Other Operators:
( ) cast
sizeof
?:
Ex - avg = float(sum) / float(count);
Ex - sizeof(int)
exp1 ? exp2 : exp3
if (exp1)
exp2;
else
exp3;
Ex- x = (y>z) ? y : z;
Operator Precedence : (see table in textbook)
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Zimmer
CSCI 130
3/18/2016
Working with Character Data –
External Representation - printable character
Internal Representation - How it is represented in the computer (ASCII or EBCIDIC)
Special characters – See textbook
Converting Character digits to integers - subtract the character '0' (zero) not 48!! (48 only works for
machines that use ASCII).
Converting to lower and uppercase - include the header file cctype to use the toupper( ) and tolower( )
functions.
Accessing characters in a string using the position number string s;
s[0] = 'H';
s[1] = 'I';
s[2] = '\0'; // null terminator character must be in the string!
cout << s;
// prints: HI on the screen
Floating Point Numbers Read textbook closely…
Significant digits - leftmost nonzero digit to the rightmost nonzero digit
precision - maximum significant digits
Normalization - leftmost digit is non zero, decimal pt is assumed after the rightmost digit then floats to appropriate position based on exponent.
Ex - 120 is represented as 1200 x 10-1
+-11200
Representational Error - Arithmetic error when significant digits > precision of machine.
- underflow - trying to represent numbers that are too small
- overflow - trying to represent numbers that are too large
- Cancellation errors - error caused by adding numbers of differing magnitudes.
----Programmers working with Floating pt. numbers need Numerical Analysis -----
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Zimmer
CSCI 130
3/18/2016
User Defined Simple DataTypes
Typedef -
Creating a new name for an existing data type.
Creates self-documenting code.
typedef ExistingTypeName NewTypeName;
ex:
typedef int Boolean;
const Boolean TRUE = 1;
const Boolean FALSE = 0;
…
Boolean dataOK;
…
dataOK = TRUE;
typedef char string [256];
string InFileName, OutFileName;
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Zimmer
CSCI 130
3/18/2016
Enumerated Data Types - Ordered sequence of identifiers used in place of integers as an aid to
the programmer.
- Provides a name for the new type
- Explicitly lists all the values (enumerators) of this new type
- Compiler performs an object to integer mapping (default starts at 0)
- Easier for computer to keep track of than the programmer.
enum DataType {enumerators separated by commas};
Example:
enum DayType {SUN, MON, TUE, WED, THU, FRI, SAT};
( SUN has the integer value 0, MON has the value 1…)
enum DayType {SUN = 4, MON = 18, TUE = 22, WED,THU,FRI,SAT);
(WED value is 23, THU is 24…)
enum VowelType { ‘a’, ‘e’, ‘i’, ’o’, ’u’}
enum PlacesType { 1st, 2nd, 3rd}
// ERROR, not valid ident.
// ERROR, not legal ident.
enum StarchType { corn, rice, potato, bean} //ERROR, together these
enum GrainType {wheat, corn, rye, barley} // overlap, ident.s must be unique
enum AnimalType { rodent, cat, dog, reptile, bird, horse, sheep};
AnimalType animal1, animal2;
Assignment - Implicit type coercion is defined from enumeration type to int, but not from int to an
enumeration type.
animal1 = dog;
// does not assign “dog” or the value of a variable dog, but
assigns the value dog.
animal1 = animal2;
// valid
animal1 = 2;
// ERROR, compile time error
someInt = dog;
// valid, because of implicit type coercion
BECAFEFUL enum Boolean {FALSE, TRUE};
Boolean dataOK;
dataOK = (someInt > -1)
// ERROR, relational expressions yield an int
// Better in this case to use typedef
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Zimmer
CSCI 130
3/18/2016
Incrementing - Can increment or decrement if type casting is used.
animal1 = animal1 + 1; // ERROR, animal1 + 1 yields and integer value
animal1++;
// ERROR, same as above
animal1 = AnimalType (animal1 + 1); // Valid, type casting
for (animal1 = rodent; animal1 < sheep; animal1 = AnimalType(animal1 + 1)) // valid
Comparison - Ordinal sequence is determined by the order in enum statement, or the integer it is
mapped to.
animal1 <= bird;
switch (animal1)
{
case rodent : …
case cat: …
…
}
// valid
Input/Output - enumerated types cannot be input or output directly..
char ch1, ch2
cin >> ch1 >> ch2;
switch (ch1)
{
case ‘r’: if (ch2 = ‘o’) animal1 = rodent;
else animal1 = reptile;
case ‘c’ : animal1 = cat;
…
}
User-Written Header files
 create your own header files in your directory
 need to use the preprocessor directive to include in your program:
#include “filename.h”
ex:
#include “bool.h”
// typedef & const for boolean values
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