Simple Data Types

1. Simple Data Types Built-In and User Defined Chapter 10

2. Built-In Simple Types • Simple (or "atomic") • Each value is indivisible, a single entity • Examples • int, char, float • NOT simple types • strings, arrays, structs

3. Characteristics of Simple Types • An object of a given type uses a specific number of bytes • sizeof( ) function will give how many • int => 2 bytes • float => 4 bytes (on our Borland C++) • An object of a simple type has a range of values • low to high • range is limited by size allocated to the type

4. Integral Types • Include • char, short, int, long • can be signed or unsigned • signed integer stored in 2 bytes • range is -32768 … 32767 • Constants can be specified in • decimal, octal, hex • normally in decimal

5. Floating Point Types • Stored in scientific notation • Include • float, double, long double • Float stored in 8 bytes • 5 - 6 significant digits • range  3.4 E  38

6. Assignment Operators & Expressions • Assignment operator = • Syntax : variable = expression; • Statement has • a value of the expression • value stored in variable location • Value previously stored in variable is now wiped out

7. Combined Assignment Operators • Considera += 5; // same as a = a + 5; • Similar results with-= *= /= %= • The symbol += is considered a binary operator • syntax requires a variable on the left • an expression on the right

8. Increment & Decrement Operators • a++; // a unary operator which increments a by 1same as a = a + 1; or a += 1; • Similar results with -- • ++ and -- work only on variables … not constants • Consider cout << a++; and cout << ++a; • post increment prints, then increments • pre-increment increments first, then prints

9. Bitwise Operators • Operators <<, >> , & , and | • Used for manipulating individual bits within memory • << and >> for shifting bits • Most of what we do will use && and || for logical AND and OR

10. The Cast Operator • Wen mixing data types in expressions, implicit type casting occurs • Example int x; float f;Consider x = f;Versus f = x; • Text suggests explicit type castingx = (int)f; // use the type in ( ) f = float(x); // use the type as a function

11. The sizeof Operator • A unary operator • yields size (in bytes) of some variable or data type • almost acts as a function • cout << sizeof (part_struct); • Often used for arrays or structs where you need to specify number of bytes to be read in or sent to a file

12. The Selection Operator ? : • A trinary operator -- requires three operands • Exampleamt = (x < 5) ? y : z; • If x < 5 then amt gets value stored in yotherwise gets value stored in z

13. Operator Precedence • Similar to algebraic precedence • Parentheses, unary, mult, div, addn, subt • Note page A1 Appendix B • Note also that some are L-> R, others are R-> L:

14. Character Data • Char is actual considered a subset of int • uses 1 byte of memory • Since it is subset of int, it can store numbers or characterschar c1, c2;c1 = 12;c2 = 'A' // Both are legal

15. Character Sets • External representation => what you see printed on screen or printer • Internal representation => bit form for storing the data in the computer memory • Most machines we encounter will use ASCII character set • Other machines use EBCDIC • Appendix D, pg A9 has examples of both

16. C++ char Constants • Single printable character enclosed by single quotes'A' '7' '$' • can be letters, numerals, or symbols • Control characters (non printable characters) used to control output'\n' for newline (same as endl)'\f' for form feed'\t' for tab'\a' for beep

17. Comparing Characters • Use comparison operators< == >= etc. • Consider if (ch >= 'a' && ch <= 'z') ...This checks to see if ch is in the lower case characters • Equivalent is if (islower (ch)) … • found in ctype.h • Check out character-testing library functions in Appendix C, pgs A2-A4

18. Convert Digit Characters to Integers • Possible to do arithmetic with characters • they are basically, integers • Examplechar ch;cin >> ch;num = ch - '0';

19. Converting Lowercase to Uppercase • From ctype.h header file, use functions providedch = toupper (ch);ch = tolower(ch): • Change only made if ch "needs" to be changed • if it is already uppercase, toupper( ) does nothing

20. Representing Floating Point Numbers • Precision of 5 or 6 significant digits • Represented internally in scientific notationFour bytes will store • sign bit for the number • 5 or 6 significant digits • sign bit for the power •  38 range for the power

21. Arithmetic with Floating Point Numbers • May lose accuracy due to round off error • especially when combining very large with very small numbers • Warnings • don't use floats to control loops • don't compare floats for equality, rather compare for closenessif ( abs (a - b) < 0.0001) …

22. Implementation of Float on a Computer Significant digits: from 1st nonzero digit on left to last non zero digit on right Precision: max number of significant digits 1.200000000000345 • Example: 1.2345E-4 Representational Error:The arithmetic error when precision of true results greater than precision for machine

23. Implementation of Float on a Computer • Underflow • results of calculation too small to be represented1.3E10 + 4.5E-10 • Overflow • value of calculation too large to be stored5.6E20 * 7.8E30 • C++ does not define results when this occurs, usually garbage values

24. The Typedef Statement • Syntax:typedef existing_type_name new_type_name; • Example:typedef int Boolean; • Does not really create a new type • is a valuable tool for writing self-documenting programs

25. Enumerated Types • Possible to create a new type by simply listing (enumerating) the constants which make up the type • Example:enum daysOfWeek (SUN, MON, TUE, WED, THU, FRI, SAT);daysOfWeek today, tomorrow, work_day;work_day = MON; • C++ represents these internally as numbers (0 .. 6 for our example)

26. Enumerated Types • Incrementing variables of an enumerated type • Do NOT use workaday += 1; NOR today++; • Instead, use explicit type conversiontoday = daysOfWeek (today + 1);

27. Enumerated Types • Comparison • normal, OK • in order of the enumeration definition • I/O • generally not possible to do directly • can be sort of done, indirectly • Used primarily for program control, branching, looping • Possible to have functions return an enumerated type

28. Named and Anonymous Data Types • Named Type • user defined type • declaration includes typedef • As with daysOfWeek or Boolean • Anonymous Type • does not have an associated typeenum (MILD, MEDIUM, HOT) salsa_sizzle; • variable declared without typedef

29. User-Written Header Files • For your collection of handy identifiers • type such as our Boolean type definition • use #include "bool.h" • note use of " " rather than < > • Tells the computer to go looking at the logged directory for bool.h file and include/insert it into the source code.

30. Type Coercion in Expressions Expression result is of type int • If two operands are of different types • one is temporarily "promoted" or "widened" to match the data type of the otherint x = 5;float f = 1.234, amt = + f; • Another example: • char or short operands promoted to intint x = 5 + 'Q';

31. Type Coercion in Assignments x | 3 Memory • Can result in "demotion" or "narrowing" • Assigning a float to an integer variable int x = 3.456; • decimal portion of float is lost • This loss of data can be considered a problem or a feature!