lecture2

lecture2 - Monday, Oct 11 stions about Proje #1? ct Que e...

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Monday, Oct 11 th Questions about Project #1? Week 1 review challenge A potpourri of new topics More about variables New operators (+=, ++, etc.) The if statement String variables…
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Time for your favorite game! Programming Language Inventor Or Serial Killer See if you can guess who uses a keyboard and who uses a chainsaw!
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Review Challenge This program computes the average of 2 numbers and prints the result. Find the syntax & semantic errors. #include <iostream> int main(void) { int sum, a, b; std::cout << “Enter 2 numbers:\n“; std :: cin >> a; sum = sum + a; std::c in >> b sum = sum + b; sum = sum / 2; std::cout >> “Average: “ + sum; ; )
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Review Challenge #include <iostream> int main(void) { int n; std::cout << “Enter n: “; std::cin >> n; // add your code here std::cout << ; std::cout << ; std::cout << ; } Given a number, n , in seconds, print out the number of hours, minutes and seconds that n represents. Hint : Use regular division and modulo division E.g. if the user types in 7265, the program should print: Hours: 2 Minutes: 1 Seconds: 5
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More About Variables Learn how to use char variables. Learn how to initialize more than one variable at a time Learn about const variables Learn some new C++ operators Linda writes her first C++ program…
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char variables int main(void) { char small_num; small_num = -125; // this is OK! Last time we learned that char variables can hold numbers between -127 and 128. To assign a symbolic value to a character variable, use single quotation marks ‘ and ’. You print out character variables just like you do any other variable. A char variable can also hold a symbolic character, like a letter or a punctuation mark. char grade, punct; grade = ‘ A ’; punct = ‘ $ ’; cout << “Your grade is: “ << grade; }
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char variables #include <iostream> int main(void) { char grade; cout << “Enter desired grade: “; cin >> grade; cout << “You don’t deserve a “ << grade; } You can also prompt the user to input a single character using std::cin . The user can type in a single character and then hit the enter key. grade ‘P’ Enter desired grade: B ‘B’ You don’t deserve a B
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#include <iostream> int main(void) { int a, b, c; a = b = c = 5; } Assigning Multiple Variables at The Same Time Sometimes its convenient to assign many variables to the same value at once. This is how you do it. #include <iostream> int main(void) { int a, b, c; c = 5; b = c; a = b; } And here’s how C++ treats it.
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Const Variables What’s wrong with this program? #include <iostream> int main(void) { double rad; std::cout << “Enter the radius of your zit: “; std::cin >> rad; std::cout << “Zit circumference: “ << 2 * rad * 3.141; std::cout << “Zit area: “ << rad*rad * 3.141; } Hint: 1.What do we have to do to our program to get increased precision (3.141 ->3.14159)?
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Const Variables #include <iostream> int main(void) { const double PI = 3.14; double rad; std::cout << “Enter the radius of your zit: “; std::cin >> rad; std::cout << “Zit circumference: “ << 2 * rad * PI ; std::cout << “Zit area: “ << rad*rad * PI ; } Use const variables when you have a value that is fixed (like , П the speed of light, etc.), and is used multiple times in your program. 3.141592653; You can define your constant variable at the top of your program once and then use it over and over. Then you can be sure you use the exact same value everywhere in your program.
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