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CS 1400

CS 1400. Pick ups from chapters 2 and 3. #include directive. This pre-processing directive causes the textual contents of a named file to be inserted into a program file at this point.

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CS 1400

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  1. CS 1400 Pick ups from chapters 2 and 3

  2. #include directive • This pre-processing directive causes the textual contents of a named file to be inserted into a program file at this point. • Include files typically contain information necessary to use externally-defined utilities (such as I/O, math, etc.)

  3. Character variables • A variable of type char can hold one character; char sex; • A character constant is delimited by single quotes; sex = ‘f’; if (sex == ‘m’) cout << “male”;

  4. char vs. literals • A literal is different from a character! char c; cout << “hello world”; c = “hello world”; // ERROR! c = ‘h’; // CORRECT c = “h”; // ERROR!

  5. *FYI variable types (Visual C++)

  6. *FYI Determining the size of variables • The library function sizeof() can be used to determine the size of variables or types on other systems: cout << sizeof (float);

  7. *FYI Constants • C++ allows the programmer to control the type and base of a constant cout << 32; // defaults to int cout << 32L; // becomes long cout << 3.14; // defaults to double cout << 3.14F; // becomes float cout << 032; // becomes base-8 or 26 cout << 3.14e-3; // becomes .00314

  8. Named constants • Constants may be given symbolic names to represent them in a program; • Form: consttype name = value; • Example: const float PI = 3.14159; const int SIZE = 24; • Alternative Form: #definename value #define PI 3.14159 #define SIZE 24 Defines should be place above main()

  9. cin I/O rules • Only digit characters (and sign) can be entered for an int variable. • Only digit, decimal, and possibly E-notation characters (and sign) can be entered for a float variable. • Only printable characters can be entered for a char variable.

  10. Strings or char arrays • A message or string of characters can be stored in a special array variable; char word[80]; // holds <80 characters cin >> word; cout << word << endl; • Only printable characters can be input using cin (no blanks, tabs, etc.)

  11. Initially limit use of string arrays… • For now, only input and output will be done on arrays; cin >> word; // OK cout << word; // OK word = “hello world”; // ERROR! if (word < “goodbye”) // ERROR! word1 = word2; // ERROR!

  12. Combining assignments • Multiple assignment statements may be combined • Example: a = b = c = 25; • Shorthand notation for combining arithmetic operations and assignment • Example: a = a * 2; same as a *= 2; b = b – 5; same as b -= 5; c = c / 7; same as c /= 7;

  13. Additional shorthand notation… • incrementing a variable value++ same as value = value + 1 • decrementing a variable value-- same as value = value - 1

  14. Formatting output • Requires: #include <iomanip> • cout manipulators: setw(n) • (set the minimum spaces for the next value output) setprecision(n) • (set the precision or rounding for a float value) fixed • (force output of float values in fixed-point notation) showpoint • (show a decimal point with trailing zeros)

  15. Controlling input • Requires #include <iomanip> • cin manipulators setw(n) • do not input more than n-1 characters for the next variable textbook error, pg 128 char word[5]; cin >> setw(5) >> word; // user enters “Eureka” cout << word; // program outputs “Eure”

  16. Special input examples… char sentence[20], ch; cin.getline(sentence, 20); • reads all characters on a line (up to 19 in count) from the keyboard and stores them in array sentence cin.get(ch); • reads the next input character (including white spaces) cin >> ch; • reads the next printable character (ignoring white spaces) cin.ignore (); • ignore (discard) the next input buffer character

  17. More math library functions… Requires: #include <cmath> functions examples abs y = abs(x); sqrt y = sqrt(a*a + b*b); log y = log(x); sin y = sin(x+z); cos y = cos(x); tan y = tan(x); etc…

  18. File Output Requires: #include <fstream> ofstream fout; fout.open (“report.txt”); fout << “hello from a file!\n”; fout.close(); To write to report.txt on the a: drive; fout.open (“a:\\report.txt”); fout.open (“a:report.txt”); fout.open (“a:\report.txt”); // ERROR!

  19. File Input Requires: #include <fstream> int a, b; ifstream fin; fin.open (“report.txt”); fin >> a >> b; cout << “sum is: “ << a+b << endl; fin.close();

  20. Example… • Write a program to generate a monthly report of concert hall business for a touring show. Up to 20 concerts are given. • assume: reserved seat tickets $80 stadium seat tickets $50 standing tickets $35 production company gets 80%

  21. Input file… line 1: tour name line 2: reserved stadium standing line 3: … line n: -1 -1 -1 Example: • Rolling Stones Geriatric Tour • 7500 4110 • 7320 4098 • 6432 2456 • -1 -1 -1 a:tour.txt

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