C++ Basics

1. C++ Basics Prof. Shermane Austin

2. Learning Programming Language Basics • Data Types – simple • Expressions • Relational and Logical Operators • Conditional Statements • Arrays • Iteration • Memory Allocation • I/O • Functions

3. Hello World //Simple C++ program #include <iostream> //input and output library #include <string> //string library using namespace std; // predefined objects int main() //first function, { //function delimiter cout << “Hello world!” << endl; //output stream return 0; //ends execution and returns ]

4. Simple Data Types • Int – 32 bit, optional qualifiers: long, short • Float – 32 bit, IEEE floating point • Double – 64 bit, optional qualifer: long • Char – 8 bit • Byte – 8 bit

5. Operators • Arithmetic • +, -, /, * • % - modulus or remainder, integer only, e.g. 23%4 • Relational • <, >, <=, >=, !=, == • (c == a) \\ common error is omitting one of the = • Be careful using != or == with floating point values, rounding occurs at the machine level • Logical • And &&, e.g. (c <= a) && (c >= b) • Or ||, e.g. (c <= a) || (c >= b)

6. Operator shortcuts – Compound Assignment • Increment, Decrement ++, -- a = a + 1; \\can be written as a++; a++, ++a, a--, --a Position of operator is important, e.g. b = f(a++); \\a is incremented after f(a) call c = f(++a); \\a is incremented before f(a) call • Compound Assignment Operators int a; … a = a + 5; a += 5; Can be used with all arithmetic operators

7. Exercise - 1 • Compute volume of an object • Read in: • Object mass (grams) • Object density (grams per cubic centimeter) • Output: Volume (cubic centimeters) • Relationship: Density = Mass/Volume

8. Code Needs • Determine variables (with types needed) • Issue prompts – use cout, e.g. Cout << “Object Mass?” << endl; • Read in values – use cin, e.g. Cin >> mass; • Compute Distance and Velocity

9. Conditional Expressions • Any combination of logical and relational operators • Use () as needed • Examples: Simple if statement if( a < b) s1 else s2

10. If/else statement • General format – single statement execution on true condition • Long format – multiple statement execution on true condition • General rule: more than one statement under if and/or else condition requires {} • Short-hand format – single statement • Nested if statements

11. If – single statement Format: if(expression) s1; else s2;

12. If – multiple statements Format: if(expression) { s1; s2; … } else { s1; s2; … }

13. If shorthand • Used only with single statements • Format: Expression ? S1 : s2; Example: c != b ? c++ : b++; Example: int a,b; … int min = a <= b ? a : b ;

14. Short-circuit evaluation • && - evaluation terminates with first false condition • || - evaluation terminates with first true condition • Done to insure objects can be properly manipulated, e.g. • (i != 0) && ((j/i) > 5)

15. Arrays • Included in C++ for backward compatibility with C • Arrays less popular and class representation of lists, especially the vector class more frequently used • Vector class is an example of container classes is defined in the Standard Template Library (STL)

16. Simple arrays - Declaration const int N = 20; const int M = 40; const int MaxListSize = 1000; // Note: const qualifier used to denote constant values //Declaration examples: int a[10]; float c[M*N]; int Values[MaxListSize];

17. Simple Arrays - Referencing • Array elements are referenced using subscripts or indices • First index in C++ is 0 • Examples: a[0] = b; a[i++] = a[j] + 3; a[a[k]] = 12; • Warning: No automatic checking for array boundaries. Illegal subscripts will result in inaccurate memory references or storage

18. Simple Array - Initialization • Int frequency[5] = {0,0,0,0,0}; • Int total[5] = {0}; // first element set to 0, remainder are uninitialized and default at 0 • Int digits[] = {0,1,2,3,4,5,6,7,8,9}; • Int zero[] = {0}; //one-element array

19. Iteration • For-loops • While-loops

20. Iteration using while • Format: while (conditional expression) { s1; … } Statement in the block are executed as long as condition is true If condition is evaluated to false, statements are never executed

21. Interation using for • Format: for (ForInit ; ForExpression; PostExpression) { } ForInit – initialization step to start loop ForExpression – logical expression PostExpression – next iteration of loop

22. For examples for( i = 0; i<= maxsize; i++) { } for(j=minsize; j < maxsize; j+=2) { } for(k = maxsize; k > minsize; k--) { }

23. Exercises • Compute n! using a for loop • Compute the nth Fibonacci term using a while loop

24. Example, compute roots of a quadratic equation: //Quadratic roots #include <iostream> #include <string> #include <math.h> Using namespace std; int main() { double a, b, c; cout << “Coefficients for quadratic equation: “; cin >> a >> b >> c; if ((a != 0) && ((b*b – 4*a*c) > 0)) { double radical = sqrt(b*b – 4 * a * c); double root1 = (-b + radical) / (2 * a); double root2 = (-b – radical) / (2 * a); cout << “ roots are “ << root1 << “ and “ << root2 << endl; } else { cout << “ No real roots “ << endl; } return 0; }

25. Compute area of a circle #include <iostream> #include <string> Using namespace std; const float Pi = 3.1415 int main() { float radius; cout << “Enter radius: ”; cin >> radius; //compute area float area = Pi * radius * radius; //output cout << “Area = “ << area; }

26. More general using functions #include <iostream> #include <string> Using namespace std; float CircleArea(float r) { const float Pi = 3.1415; return Pi * r * r; } int main() { float radius; cout << “Enter radius: ”; cin >> radius; //compute area float area = CircleArea(radius); //output cout << “Area = “ << area; }

27. Function prototyping • Functions cannot be used until they are defined • Can create problems with functions calling other functions • Use prototype conventions • Define function prototype before main • Implement function after main

28. Prototype Example #include <iostream> #include <string> Using namespace std; float CircleArea(float r); int main() { float radius; cout << “Enter radius: ”; cin >> radius; //compute area float area = CircleArea(radius); //output cout << “Area = “ << area; } float CircleArea(float r) { const float Pi = 3.1415; return Pi * r * r; }

29. Homework • Write a program for integrating a quadratic polynomial • User input will be • Quadratic coefficients: a1, a2, a3 • Interval of interest : n1, n2 • Output will be the area