1. 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

2. 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

3. 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); }

4. 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

5. 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

6. 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;

7. 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)

8. 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.

9. 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.

10. 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.

11. 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)

12. 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.

13. 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);

14. 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.