1. Chapter 7 Introduction to High-Level Language Programming

2. Where Do We Stand? Machine language Assembly language LOAD X ADD ONE STORE X. ONE:.DATA 1 Equivalent to INCREMENT X Fine-tuning

3. Disadvantages of Assembly Language Manually manage the movement of data items between and among memory locations. Must take a microscopic view of a task Machine-specific Statements are not English-like

4. High-level Programming Language Data management is much easier. Take a macroscopic view of tasks. High-level languages are more portable. Closer to standard English, use standard mathematical notation. High-level programming languages are often called third-generation language.

5. Program Translation Need a translator to convert high-level language instructions into machine languages. Such a system software is called a compiler. Code library Linker

6. Translations of High-Level Language Refer to Figure 7.1. Source program  translation(compiler)  intermediate program (assembly language code)  translation (assembler)  object program(object code in machine language)  Linker (links with library object code)  complete object code(executable)  loader  complete object code loaded into memory  hardware (execution)  results

7. The C++ Language Developed in the 1980s by Bjarne Stroustrup at AT&T Bell labs. Extension of C Object-oriented (more on this topic later)

8. 1// Fig. 1.2: fig01_02.cpp 2// A first program in C++ 3#include 4 5int main() 6{6{ 7 std::cout << "Welcome to C++!\n"; 8 9 return 0; // indicate that program ended successfully 10} Welcome to C++! preprocessor directive Message to the C++ preprocessor. Lines beginning with # are preprocessor directives. #include tells the preprocessor to include the contents of the file, which includes input/output operations (such as printing to the screen). Comments Written between /* and */ or following a //. Improve program readability and do not cause the computer to perform any action. C++ programs contain one or more functions, one of which must be main Parenthesis are used to indicate a function int means that main "returns" an integer value. More in Chapter 3. A left brace { begins the body of every function and a right brace } ends it. Prints the string of characters contained between the quotation marks. The entire line, including std::cout, the << operator, the string "Welcome to C++!\n" and the semicolon ( ; ), is called a statement. All statements must end with a semicolon. return is a way to exit a function from a function. return 0, in this case, means that the program terminated normally.

9. Overall Form of a C++ Program Prologue comment[optional] Include derivatives[optional] Functions[optional] Main function { declarations[optional] main function body }

10. Virtual Data Storage Can associate data with a more meaningful name called identifier. In C++, an identifier can be any combination of letters,digits and the underscore symbol (_), as long as it does not begin with a digit. Cannot use keywords for identifiers, either. C++ is a case-sensitive language. Constants vs. variables

11. C++ Keywords Cannot be used as identifiers or variable names.

12. Declaration Tells whether the data item is a constant or a variable. Tells the identifier that will be used throughout the program to name the item. Tells the data type for that item. e.g. double Radius;

13. C++ Syntax Syntax: the correct form for each component of the language. C++ is a free-format language, it does not matter where things are placed on a line. const double PI = 3.1416; int grades[50]; int image[256][256];

14. 2-D Array [0][0]=14.3, [0][1]=15.2, [0][2]=16.4 [1][0]=13.9, [1][1]=14.2, [1][2]=12.7  Data structure Site 1Site 2Site 3 Final reading 14.315.216.4 Initial reading 13.914.212.7

15. Statement Types Input/output statements Assignment statements Control statements

16. Input/output Statements Get the value for radius: cin >> Radius; extraction operator >> iostream library #include Print the value of circumference cout << Circumference; insertion operation <<

17. Output format Fixed-point format: 84.8232 Scientific notation (floating-point format): 8.482320e+001 #include cout.setf(ios::fixed); cout.setf(ios::scientific); cout.precision(2); setw(8);

18. The Assignment Statement Set the value of “ variable ” to “ arithmetic expression ” variable=expression; B=2; C=5; A=B+C; A=A+1; +,-,*,/,% (mod) Changing data type: type casting

19. Control Statements Sequential (default, no action required) Conditional Looping

20. C++ Comparison and Boolean Operators Comparison operators: ==,, >=, != Boolean operators && (AND), || (OR), ! (NOT)

21. Conditional Statements if-else if Nested-if

22. 1// Fig. 1.14: fig01_14.cpp 2// Using if statements, relational 3// operators, and equality operators 4#include 5 6using std::cout; // program uses cout 7using std::cin; // program uses cin 8using std::endl; // program uses endl 9 10int main() 11{ 12 int num1, num2; 13 14 cout << "Enter two integers, and I will tell you\n" 15 << "the relationships they satisfy: "; 16 cin >> num1 >> num2; // read two integers 17 18 if ( num1 == num2 ) 19 cout << num1 << " is equal to " << num2 << endl; 20 21 if ( num1 != num2 ) 22 cout << num1 << " is not equal to " << num2 << endl; 23 24 if ( num1 < num2 ) 25 cout << num1 << " is less than " << num2 << endl; 26 27 if ( num1 > num2 ) 28 cout << num1 << " is greater than " << num2 << endl; 29 30 if ( num1 <= num2 ) 31 cout << num1 << " is less than or equal to " 32 << num2 << endl; 33 The if statements test the truth of the condition. If it is true, body of if statement is executed. If not, body is skipped. To include multiple statements in a body, delineate them with braces {}. Enter two integers, and I will tell you the relationships they satisfy: 3 7 3 is not equal to 7 3 is less than 7 3 is less than or equal to 7 Notice the using statements.

23. 34 if ( num1 >= num2 ) 35 cout << num1 << " is greater than or equal to " 36 << num2 << endl; 37 38 return 0; // indicate that program ended successfully 39} Enter two integers, and I will tell you the relationships they satisfy: 3 7 3 is not equal to 7 3 is less than 7 3 is less than or equal to 7 Enter two integers, and I will tell you the relationships they satisfy: 22 12 22 is not equal to 12 22 is greater than 12 22 is greater than or equal to 12 Enter two integers, and I will tell you the relationships they satisfy: 7 7 7 is equal to 7 7 is less than or equal to 7 7 is greater than or equal to 7

24. Nested if/else Structures Test for multiple cases by placing if/else selection structures inside if/else selection structures. if student ’ s grade is greater than or equal to 90 Print “ A ” else if student ’ s grade is greater than or equal to 80 Print “ B ” else if student ’ s grade is greater than or equal to 70 Print “ C ” else if student ’ s grade is greater than or equal to 60 Print “ D ” else Print “ F ” Once a condition is met, the rest of the statements are skipped

25. Looping while (Boolean condition) S1; Initialization of variables. Sentinel value: to signal that there are no more data. Infinite loop

26. 1// Fig. 2.7: fig02_07.cpp 2// Class average program with counter-controlled repetition 3#include 4 5using std::cout; 6using std::cin; 7using std::endl; 8 9int main() 10{ 11 int total, // sum of grades 12 gradeCounter, // number of grades entered 13 grade, // one grade 14 average; // average of grades 15 16 // initialization phase 17 total = 0; // clear total 18 gradeCounter = 1; // prepare to loop 19 20 // processing phase 21 while ( gradeCounter <= 10 ) { // loop 10 times 22 cout << "Enter grade: "; // prompt for input 23 cin >> grade; // input grade 24 total = total + grade; // add grade to total 25 gradeCounter = gradeCounter + 1; // increment counter 26 } 27 28 // termination phase 29 average = total / 10; // integer division 30 cout << "Class average is " << average << endl; 31 32 return 0; // indicate program ended successfully 33} The counter gets incremented each time the loop executes. Eventually, the counter causes the loop to end.

27. Enter grade: 98 Enter grade: 76 Enter grade: 71 Enter grade: 87 Enter grade: 83 Enter grade: 90 Enter grade: 57 Enter grade: 79 Enter grade: 82 Enter grade: 94 Class average is 81

28. 1// Fig. 2.9: fig02_09.cpp 2// Class average program with sentinel-controlled repetition. 3#include 4 5using std::cout; 6using std::cin; 7using std::endl; 8using std::ios; 9 10#include 11 12using std::setprecision; 13using std::setiosflags; 14 15int main() 16{ 17 int total, // sum of grades 18 gradeCounter, // number of grades entered 19 grade; // one grade 20 double average; // number with decimal point for average 21 22 // initialization phase 23 total = 0; 24 gradeCounter = 0; 25 26 // processing phase 27 cout << "Enter grade, -1 to end: "; 28 cin >> grade; 29 30 while ( grade != -1 ) { Data type double used to represent decimal numbers.

29. 31 total = total + grade; 32 gradeCounter = gradeCounter + 1; 33 cout << "Enter grade, -1 to end: "; 34 cin >> grade; 35 } 36 37 // termination phase 38 if ( gradeCounter != 0 ) { 39 average = static_cast ( total ) / gradeCounter; 40 cout << "Class average is " << setprecision( 2 ) 41 << setiosflags( ios::fixed | ios::showpoint ) 42 << average << endl; 43 } 44 else 45 cout << "No grades were entered" << endl; 46 47 return 0; // indicate program ended successfully 48} Enter grade, -1 to end: 75 Enter grade, -1 to end: 94 Enter grade, -1 to end: 97 Enter grade, -1 to end: 88 Enter grade, -1 to end: 70 Enter grade, -1 to end: 64 Enter grade, -1 to end: 83 Enter grade, -1 to end: 89 Enter grade, -1 to end: -1 Class average is 82.50 setiosflags(ios::fixed | ios::showpoint) - stream manipulator ios::fixed - output numbers with a fixed number of decimal points. ios::showpoint - forces decimal point and trailing zeros, even if unnecessary: 66 printed as 66.00 | - separates multiple option. setprecision(2) - prints only two digits past decimal point. Programs that use this must include static_cast () - treats total as a double temporarily. Required because dividing two integers truncates the remainder. gradeCounter is an int, but it gets promoted to double.

30. Meeting Expectations Data management issue Macroscopic view Portability: ANSI standard Closer to human-language

31. Keeping the Pieces Apart Divide and conquer Using functions Function name (identifier) Argument list: what to pass, what gets returned(return indicator) Local vs. global variables Pass by value vs. pass by reference

32. 1// Fig. 3.12: fig03_12.cpp 2// A scoping example 3#include 4 5using std::cout; 6using std::endl; 7 8void a( void ); // function prototype 9void b( void ); // function prototype 10void c( void ); // function prototype 11 12int x = 1; // global variable 13 14int main() 15{ 16 int x = 5; // local variable to main 17 18 cout << "local x in outer scope of main is " << x << endl; 19 20 { // start new scope 21 int x = 7; 22 23 cout << "local x in inner scope of main is " << x << endl; 24 } // end new scope 25 26 cout << "local x in outer scope of main is " << x << endl; 27 28 a(); // a has automatic local x 29 b(); // b has static local x 30 c(); // c uses global x 31 a(); // a reinitializes automatic local x 32 b(); // static local x retains its previous value 33 c(); // global x also retains its value 34 x is different inside and outside the block. local x in outer scope of main is 5 local x in inner scope of main is 7 local x in outer scope of main is 5

33. 3.1 Define Functions 35 cout << "local x in main is " << x << endl; 36 37 return 0; 38} 39 40void a( void ) 41{ 42 int x = 25; // initialized each time a is called 43 44 cout << endl << "local x in a is " << x 45 << " after entering a" << endl; 46 ++x; 47 cout << "local x in a is " << x 48 << " before exiting a" << endl; 49} 50 51void b( void ) 52{ 53 static int x = 50; // Static initialization only 54 // first time b is called. 55 cout << endl << "local static x is " << x 56 << " on entering b" << endl; 57 ++x; 58 cout << "local static x is " << x 59 << " on exiting b" << endl; 60} 61 62void c( void ) 63{ 64 cout << endl << "global x is " << x 65 << " on entering c" << endl; 66 x *= 10; 67 cout << "global x is " << x << " on exiting c" << endl; 68} Local automatic variables are created and destroyed each time a is called. Local static variables are not destroyed when the function ends. Global variables are always accessible. Function c references the global x. local x in a is 25 after entering a local x in a is 26 before exiting a local static x is 50 on entering b local static x is 51 on exiting b global x is 1 on entering c global x is 10 on exiting c

34. local x in outer scope of main is 5 local x in inner scope of main is 7 local x in outer scope of main is 5 local x in a is 25 after entering a local x in a is 26 before exiting a local static x is 50 on entering b local static x is 51 on exiting b global x is 1 on entering c global x is 10 on exiting c local x in a is 25 after entering a local x in a is 26 before exiting a local static x is 51 on entering b local static x is 52 on exiting b global x is 10 on entering c global x is 100 on exiting c local x in main is 5

35. 1// Fig. 3.20: fig03_20.cpp 2// Comparing call-by-value and call-by-reference 3// with references. 4#include 5 6using std::cout; 7using std::endl; 8 9int squareByValue( int ); 10void squareByReference( int & ); 11 12int main() 13{ 14 int x = 2, z = 4; 15 16 cout << "x = " << x << " before squareByValue\n" 17 << "Value returned by squareByValue: " 18 << squareByValue( x ) << endl 19 << "x = " << x << " after squareByValue\n" << endl; 20 21 cout << "z = " << z << " before squareByReference" << endl; 22 squareByReference( z ); 23 cout << "z = " << z << " after squareByReference" << endl; 24 25 return 0; 26} 27 28int squareByValue( int a ) 29{ 30 return a *= a; // caller's argument not modified 31} Notice the use of the & operator

36. x = 2 before squareByValue Value returned by squareByValue: 4 x = 2 after squareByValue z = 4 before squareByReference z = 16 after squareByReference 32 33void squareByReference( int &cRef ) 34{ 35 cRef *= cRef; // caller's argument modified 36}