Solution to Midterm Exam 1. What is the output? #include <stdio.h> main() { int i, j, k; i = 2; j = 5; k = 0; if(i == j) printf("i equals j\n"); else { while(j>k) { printf("%d\n", j); --j; ++k; } 5 4 3

Solution to Midterm Exam 2. What is printed? #define VAL 4 #include <stdio.h> main() { int a[3]; a[0] = 1; a[1] = -1; a[2] = VAL; printf("%d\n", a[0] < 1 || a[1] != 1); printf("%d\n", !a[1]); printf("%d\n", a[0] | a[1]); printf("%d\n", a[a[0]+1]); } 1 -1 4

Solution to Midterm Exam 3. Write a program that read standard input character by character, and print out the characters to the standard output, replacing spaces ' ' by underscores '\_'. You can use while loop, getchar(), and putchar() functions. #include <stdio.h> main() { int c; while( (c=getchar()) != EOF) { if(c == ' ') putchar('_'); else putchar(c); }

Quizzes What is the output? #include <stdio.h> main() { char *s = "ABC xyz"; printf("%s\n", s+4); printf("%c\n", s[4]); printf("%c\n", *s); printf("%s\n", &s); } xyz x A P^U

Quizzes What is the output? 11, 2, 13, 13, 10 #include <stdio.h> int i; void func(int j, int *p, int a[]); main() { int j, k, *p, a[1]; i = 1; j = 2; k = 3; p = &k; a[0] = 0; func(j, p, a); printf("%d, %d, %d, %d, %d\n", i, j, k, *p, a[0]); } void func(int j, int *p, int a[]) i += 10; j += 10; *p += 10; a[0] += 10; p = &i; 11, 2, 13, 13, 10

Quizzes Write a function (with a name of your choice) which take a string and returns an int. If the string looks the same when read forward and backward, return 1, else return 0. #include <string.h> int palindrome(char *s) { char *e; e = s + strlen(s) -1; while( s < e ) { if (*s != *e) return 0; ++s; --e; } return 1;

Looking Toward C++ Object-Oriented Design is characterized by Objects (data together with operations on the data) Classes (abstract characterizations of objects) Inheritance (code sharing) Polymorphism (run-time binding of operations to objects)

Objects The object-oriented programming emphasizes objects, which consist of data and operations on the data. For example, we may have a figures like circle or line object with the operation of drawing the figures. If c is a circle object, we invoke its draw method (operation) by passing a message to c: c.draw() While the traditional programming typically call a function like draw(CIR) where CIR is a flag to indicate which figure to draw.

Classes and Abstract Data Type A class is an abstract characterization of a set of objects. A class defines variable (data) and methods (operations) common to a set of objects. An abstract data type associates operations on the type but hides detail implementation.

Class example The following code declares a class string: char data[80]; public: void store(char*); int length(); }; The char data[80] is the data, store() and length() are methods. Only the two methods are accessible to the outside world. The data are private.

Create Objects and Invoke Method string s, t; defines two object s and t belonging to the class string. Data member is referenced by writing s.x and the method f is invoked by writing s.f(arguments) If ptr is a pointer to s, we use s -> x or s -> f(arguments)

Pass a Message to Object class string { char data[80]; public: void store(char *); int length(); } string s, t; s.store("Hi Mom"); len = s.length(); The user of the string class need not to know the implementation details.

Inheritance A new class can be defined based on an old class. All the data and associated methods becomes part of the new class. class pen { int x, y; int status; public: void set_status(int); void set_location(int, int); }; class colored_pen: public pen { int color; void set_color(int);

Polymorphism Poly : Greek word meaning many. Morphism : Greek word meaning form. Polymorphism mean many forms. In object-oriented programming, polymorphism refers to identically named methods that have different behavior depending on the type of object that they reference.