06-NumbersOperators.pdf

Transcript

1. ICS 212 Program Structure William McDaniel Albritton M.S.
2. Memory Allocation  #define  Numbers and Operators in C  Formatting Output
4. #define
5. #define  Usually at the top of the code  Used to create symbolic constants  Used to create macros
6. #define format  #define identifier replacement-text  All subsequent occurrences of identifier will be replaced before the program is compiled  Occurrences that appear in string literals (strings in double-quotes) will not be replaced
7. #define PI 3.14159265358979323846 Symbolic Constant  Creates a name for a constant in the program  NO semi-colon!!!!  Redefining a symbolic constant with a new value is an error  See example program: define.c
8. Macro  Macros enable you to name a small instruction and use the name throughout the program.  Example:  #define AREA b*h  More about this later…
10. Numbers and Operators in C
11. Data Types are System-Dependent  On UH UNIX operating system, we are using GCC  GNU Compiler Collection (GCC) is a compiler system, which was created by the GNU Project and supports languages such as C (gcc), C++ (g++), and others %gcc –v gcc version 3.4.6
12. Data Types are System-Dependent Integers char Maximum = 127 short Maximum = 32,767 int Maximum = 2,147,483,647 long Maximum = 2,147,483,647 *GCC on UH UNIX
13. Data Types are System-Dependent Floating Point float 6 digits of precision Maximum exponent 38 Maximum value 3.402823e+38 double 15 digits of precision Maximum exponent 308 Maximum value 1.797693e+308 long double 33 digits of precision Maximum exponent 4932 Maximum value 1.189731e+4932 *GCC on UH UNIX
14. Example Program  Try running this program on different platforms to see if you get different outputs  See program at: maximum.c
15. Number Representation  Integer numbers are exactly represented as binary numbers  Floating-point numbers are approximately represented as binary numbers, with three parts: sign, exponent, and mantissa  Because of round-off errors, floating-points are not exact, except for negative powers of two (0.5, 0.25, …)
16. Scientific Notation  Floating point numbers are expressed as a mantissa times a power of ten  Exponential notation: the x10n is substituted for e n  Examples:  155.97 = 1.5597x102 = 1.5597e2  2.3 = 2.3 x 100 = 2.3e0
17. Precedence of Arithmetic and Assignment Operators Precedence Operator Associativity 1 Parentheses: ( ) Innermost first 2 Unary operators: + - ++ -- (type) Right to left 3 Binary operators: * / % Left to right 4 Binary operators: + - Left to right 5 Assignment operators: = += -= *= /= %= Right to left
18. Overflow and Underflow  This occurs when numbers are either too big or too small to be stored. overflow overflow within allowed range within allowed range underflow close to zero large negative large positive
19. Integer Division  Integer division produces an integer result.  Integer division truncates  1/2  1 divided by 2 is 0  9/5  9 divided by 5 is 1
20. Modulus  The remainder after division (%)  10 % 5  10/5 = 2, remainder 0  19 % 5  19/5 = 3, remainder 4  1 % 2  1/2 = 0, remainder 1
21. Pre-Increment Operator  Increment (add one), then assign new value a = 3; b = ++a; //b = 4, a = 4
22. Post-Increment Operator  First assign value, then increment (add one) a = 3 b = a++; //b = 3, a = 4
23. Assignment Operators  x = x + 5;  Shortcut: x += 5;  a *= b + 5;  Evaluates to a = a *(b + 5);  And not a = a * b + 5;
24. Implicit Conversion  When using operands of different types, the “narrower” one will be converted to the “wider” one
25. Implicit Conversion  Examples:  1 / 3.0 (int/float) evaluates to 0.33333  1.0 / 2 (float/int) evaluates to 0.5
26. Explicit Conversion  Also know as Type Casting  Converting one data type into another by using the (datatype) operator  Usually implies a potential loss of data precision.
27. Explicit Conversion  variable2 = (datatypeOfVariable2) variable1;  See example program at: number.c double number1 = 12.34; int number2 = 0; number2 = (int)number1; //number2 will be 12, loss of precision
29. Formatting Output
30. Characters  Char variables are enclosed in single quotes: 'a'  Don’t forget that integer 3 is not the same as character '3' char letter = 'a'; //0x61 char integer3 = 3; //0x03 char letter3 = '3'; //0x33
31. printf  The printf function allows us to print to standard output (the screen)  printf statements usually contain  Control string: To label the output  Conversion specifier: To format the output  Argument: What needs to be printed
32. Conversion Specifiers Variable Type Output Type Specifier Integer Values char, short, int int %i, %d int short %hi, %hd long long %li, %ld int unsigned int %u int unsigned short %hu long unsigned long %lu
33. Conversion Specifiers Variable Type Output Type Specifier Floating-Point Values float, double double %f, %e, %E, %g, %G long double long double %LF, %Le, %LE, %Lg, %LG Character Values char char %c
34. Conversion Specifiers
35. Example Program  See example program at: output.c
36. Using Flags Flag Description - Left justify + Precede numerical values with the corresponding sign # Prefix O when using octal specifier Prefix OX when using hexadecimal specifier Forces decimal point for floating points printed with e, E, f, g or G without a fractional part For G and g, trailer zeroes are not eliminated 0 Pad a field with leading zeroes
37. Function puts()  Function puts() displays a string and a newline puts(“Aloha!”); puts(“Hey, y'all!”); /* Aloha! Hey, y'all! */
38. Example Program  See example program at: format.c
39. Memory Management  #define  Numbers and Operators in C  Formatting Output