1 CS 1430: Programming in C++

2 Literal Values Literal values of int Literal values of float

3 Positive, Negative, and Zero Is 0 positive or negative? 0 is neither positive nor negative

4 Literal Values (II) Literal values of char ‘C’ ‘A’ ‘D’ Literal values of string “Enter an integer: ” “Your Grade is ” “A”

5 Variables // Variables can have initial values int num1, total = 0; // Variables can have different values cin >> num1; num1 = 58; total = total + num1;

6 Symbolic Constants // Symbolic constant const int MAX_SCORE = 60; // Must give a value // Store in memory // Can we do this? MAX_SCORE = 100; cin >> MAX_SCORE; // Error: constant cannot change its value

7 No Magic Numbers // Define symbolic constant const int MAX_SCORE = 60; int myScore; myScore = 60; // Is this good? // NO! // Magic number! // Half points off! myScore = MAX_SCORE; // Very good!

8 The Cast Functions int num1, num2; float quotient; cin >> num1 >> num2; //No input prompt! // 3 5 quotient = num1 / num2; // what’s the value of quotient? // How to get float quotient? quotient = float(num1) / num2; // Use cast function. // coercion quotient = float(num1 / num2); // Integer division or float division? // Integer division!

9 The IF statement int num1, num2; float quotient; cin >> num1 >> num2; quotient = float(num1) / num2; // Any possible issues? // What if num2 is zero? if (num2 != 0) quotient = float(num1) / num2;

10 The IF statement int num1, num2; float quotient;... if (num2 != 0) quotient = float(num1) / num2; // Semantics // do computation only when num2 is not zero // the statement is skipped when num2 is zero // Syntax // condition inside () // != for not equal // Style // on separate lines // indent 3 spaces

11 If-Else if (num2 == 0) cout << endl << "Cannot divide by zero!"; else { quotient = float(num1) / num2; cout << endl << "The quotient is " << quotient << ‘.’; } // Semantics // do different things when num2 is zero or not // Syntax // braces for multiple statements (statement block) // == for equal // Why use “==” instead of “=”? // Style // braces on separate lines

12 If-Else if (num2 == 0) { cout << endl << "Cannot divide by zero!"; } else { quotient = float(num1) / num2; cout << endl << "The quotient is " << quotient << ‘.’; } // Syntax // braces are optional for single statement

13 Statement Block if (num2 == 0) cout << endl << "Cannot divide by zero!"; else quotient = float(num1) / num2; cout << endl << "The quotient is " << quotient; // Will the program do output when num2 is 0? // YES! // Same as the following: if (num2 == 0) cout << endl << "Cannot divide by zero!"; else quotient = float(num1) / num2; cout << endl << "The quotient is " << quotient; // Indentation and blank line is a style issue // It does not make a block

14 If-Else if (num2 == 0) { cout << endl << "Cannot divide by zero!"; } else { quotient = float(num1) / num2; cout << endl << "The quotient is " << quotient << ‘.’; } // Syntax // braces are optional for blocks of single statement // braces are required for blocks of multiple statements

15 Comparison Operators == != > >= < <= No Space between!

16 Logical Operators && // And || // Or ! // Not

17 Comparison Operators != !> // NO! <= // Yes! ≤ // NO! <= // Yes!

18 Comparing characters const char UPPER_A = 'A'; char inputChar; cout << endl << "Enter a char: ”; cin >> inputChar; if (inputChar == UPPER_A) cout << endl << “It's an A!”;

19 Examples if (inputChar >= UPPER_A && inputChar <= 'Z') cout << endl // What should be the message? << "It's an upper case letter."; inputChar = ‘C'; inputChar = inputChar + 1; cout << endl << "The next char is " << inputChar; // The next char is D inputChar = ‘C'; cout << endl << "The next value is " << inputChar + 1; // The next value is 68 cout << endl << "The next char is " << char(inputChar + 1); // The next char is D

20 Multiple Conditions int num1, num2; cin >> num1 >> num2; if (num1 > 0 && num2 > 0) cout << “Both numbers are positive.” << endl; if (num1 > 0 || num2 > 0) cout << “At least one number is positive.” << endl; if (num1 && num2 == 0) cout << “\nBoth numbers are zero.”; // NO! if (num1 == 0 && num2 == 0) cout << “\nBoth numbers are zero.”; // Good! if (num1 = 0 && num2 = 0) cout << “\nBoth numbers are zero.”; // NO! // “=” is assignment!

21 Checking Input int score1, score2; Cout << “Enter two scores between 0 and 60, inclusive.”; cin >> score1 >> score2; if (score1 >= 0 && score1 = 0 && score2 <= 60) cout << “Both numbers are in the range.” << endl; // Magic numbers! const int MAX_SCORE = 60; const int MIN_SCORE = 0; if (score1 >= MIN_SCORE && <= MAX_SCORE && score2 >= MIN_SCORE && score2 <= MAX_SCORE) cout << “Both numbers are in the range.” << endl;

22 Example: Find the MAX of two numbers int num1, num2, max; cin >> num1 >> num2; if (num1 > num2) max = num1; else max = num2; cout << “The max value is ” << max << endl; // Another way if (num1 >= num2) max = num1; else max = num2; cout << “The max value is ” << max << endl;

23 Positive or Non-Positive int x = 10, y = 7; float z = -5.0; z = y / x; z = y / float(x); if (z > 0) cout << “Positive."; else cout << "Non-Positive."; // what is the output?

24 Even and Odd Numbers const int EVEN_NUMBER_DIVIDER = 2; int theNum; cout << "Enter an integer: "; cin >> theNum; // How do we know an integer is an even number? // The remainder operator %! if ((theNum % EVEN_NUMBER_DIVIDER) == 0) cout << theNum << " is an even number."; else cout << theNum << " is an odd number.";

25 Square Root Function float theNum; cout << "Enter a number: "; cin >> theNum; // How do we compute the square root of a number? // Call function sqrt()! if (theNum >= 0) cout << “The square root of ” << theNum << “ is ” << sqrt(theNum); else cout << theNum << " is a negative number."; // Need to include header file

26 Power Function #include using namespace std; int main() { float base, expo; cout << "Enter two numbers: "; cin >> base >> expo; // How do we compute base expo // Call function pow()! if (base > 0) cout << “Base ” << base << “ raised to power ” << expo << “ is ” << pow(base, expo); else cout << “Base is not positive."; return 0; }

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