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Week 3

Week 3. In this class, you will learn about: Program Structure, Actions and Data Types Data Type: Variables Output and Input action: function cout<< & cin>> Assignment Simple calculations

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Week 3

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  1. Week 3 In this class, you will learn about: • Program Structure, Actions and Data Types • Data Type: Variables • Output and Input action: function cout<< &cin>> • Assignment • Simple calculations Reference: Programming with C++, Theory and Problems of, Second Edition; John R Hubbard (McGraw Hill, 2000, Schaum's Outline Series)

  2. Program Structure, Actions and Data Types • C++ Program Structure • #include <iostream> • main() { • cout<<"HEY, you, I'm alive!"; // output a string. • } • The program is saved as a file that should be named. In this example, the name of the file is cout1a.cpp. .cpp • The #include is called a preprocessor directive which tells the computer compiler to include the header fileiostream.h in our program cout1a.cpp. • The next part is main(). • The body of the • The lines for the body of a program is called statements, for example, cout • Comment lines

  3. Data Type: Variables • Variables • Name of a variable • A variable has a name, which is given by the programmer by declaration or definition. When the name is given, the memory for it is specified. • Rules for creating names of variables • Rule 1: a name starts with a letter. • Rule 2: a name is unique, which should be different from other words in the program. • Rule 3: names are sensitive to letters upper case or lower case. Doug is not equivalent to doug. • Rule 4: names should be meaningful.

  4. For example, int alice; name of variable: alice type: int(eger) tail: ; Data Type: Variables

  5. Data Types

  6. Part of Integral Type

  7. It shows that the 32 bits it uses to store a float are partitioned into 3 parts: 23 bits for the mantissa, 8 bits for the exponent, and 1 bit for the sign. The 23-bit mantissa produces a floating-point value with 6 significant digits, and the 8-bit exponent yields a range in magnitude from about 10–37 to about 3 × 1038. i.e., 0.0000000000000000000000000000000000001 < |x| < 300,000,000,000,000,000,000,000,000,000,000,000,000 for any variable x declared to have type float. Float type example

  8. A new variable : char (character data) • Definition • A char variable is defined to hold a single character that appears on the keyboard. • Difference between a char and a string is that a char is a single character while a string is a collection of serial characters. • Declaration • char c; • Input a char variable from keyboard • A space cannot be input from keyboard

  9. A new variable : char (character data)

  10. A new variable : char (character data)

  11. Output action: function cout<< • More actions by using a back slash \ • The sign \ is not a normal character but a control character to instruct the computer to take an action corresponding to next character. See table below, • Escape characterEffect\nNewline\tHorizontal tab\rCarriage return\bBackspace\aBell or beep\\Backslash\”Double quote\’Single quote\?Question mark

  12. Input action: input function cin>>Assignment • We have seen that one way of assigning a variable with a value is to input a number of digits on keyboard. Another important way is to use an assignment statement. For example (assignment1.cpp),

  13. Prefix and postfix increment • Example:k = ++x;//prefix increment • is equivalent to: • x = x + 1; //increment n first • k = x;//assign x’s value to k • Example:k = x++;//postfix increment • is equivalent to • k = x;//assign x’s value to k • x = x + 1;//and then increment x

  14. Applying the Pre-increment and Post-increment Operators int main() { // shows the difference between m++ and ++m: int m,n; m = 44; n = ++m; // the pre-increment operator is applied to m cout << "m = " << m << ", n = " << n << endl; m = 44; n = m++; // the post-increment operator is applied to m cout << "m = " << m << ", n = " << n << endl; }

  15. COMPOSITE ASSIGNMENT OPERATORS • The standard assignment operator in C++ is the equals sign =. In addition to this operator, C++ also includes the following composite assignment operators: +=, -=, *=, /=, and %=. • When applied to a variable on the left, each applies the indicated arithmetic operation to it using the value of the expression on the right.

  16. Applying Composite Arithmetic Assignment Operators int main() { // tests arithmetic assignment operators: int n=22; cout << "n = " << n << endl; n += 9; // adds 9 to n cout << "After n += 9, n = " << n << endl; n -= 5; // subtracts 5 from n cout << "After n -= 5, n = " << n << endl; n *= 2; // multiplies n by 3 cout << "After n *= 2, n = " << n << endl; n / = 3; // divides n by 9 cout << "After n /= 3, n = " << n << endl; n %= 7; // reduces n to the remainder from dividing by 4 cout << "After n %= 7, n = " << n << endl; }

  17. Simple calculations

  18. Simple calculations

  19. Integer Calculation Example int main() { // tests operators +,-,*,/,and %: int m=54; int n=20; cout << "m = " << m << " and n = " << n << endl; cout << "m+n = " << m+n << endl; // 54+20 = 74 cout << "m-n = " << m-n << endl; // 54-20 = 34 cout << "m*n = " << m*n << endl; // 54*20 = 1080 cout << "m/n = " << m/n << endl; // 54/20 = 2 cout << "m%n = " << m%n << endl; // 54%20 = 14 Return 0; }

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