c programming by example

8/8/2019 C Programming by Example

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Computer Based Applications

"How Software Works"

Author ~ Martin Whitbread


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This document is in two parts. The first is in sections and contains a series of

exercises that should be worked on using the DevCpp Integrated Development

Environment. These should be documented and shown on request, to your

supervisor. The second part applies many of the skills acquired in the first part todevelop a game program that emulates a Pin Ball table.

The marks applied are: Part 1 - 40%

Part 2 - 60%

Your work should NOT just be a collection of code listings but should be a

discourse where the code illustrates points. Results need to be recorded and the

results of any more interesting tests that are applied. Do NOT copy work, all

parties will be penalized if this is detected, work individually and meet deadlines.

MJW


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IntroductionIn today's world software is everywhere, often hidden from the user as an integral part of of the

system. So when a button on a remote control is pressed, or a key on a mobile phone, layers of

electronics and controlling software are activated. Programming these systems is not easy, they

have to function reliably and accurately for the live of the system. There may be health and safety

issues, with lives or property at risk if the design is not robust or the software faulty. Applications ofsoftware extend far beyond the simple PC or laptop and are much more demanding on the

designers, implementers and testers. There is no reset button on a pacemaker or a jumbo jet.

http://boeing.com/commercial

Software tools have evolved considerably over the last 40 years or so. A lot of code is

still written in a programming language, to be compiled and tested in a suitable

environment. Early languages were low level - they matched the architecture of the

processor and were specific for that machine. Later came languages such as Fortran

(Formula Translation) and COBOL (Common Business Oriented Language) which

advanced the number of scientific and business applications that could be written for

the large mainframe computers then in use. Other languages followed, including the

widely used language 'C'. While C is a relatively low level language, in includes

many high level constructs. The ability of C to process data at bit level meant that it

has been able to replace most of the machine specific assembly (low) level languages

used on embedded systems projects. The later extension of the C syntax to include

object oriented design concepts as C++ has meant that large software projects can be

built around libraries of proven objects. Other languages have been developed from

C++ , including Java and C#. The basic syntax of C stays more or less the same inthese languages. An understanding of C leads to a much better appreciation of the

logic in applications written in these languages. Progressing from C to C++ becomes

relatively easy, once an understanding of object oriented programming is achieved.

These languages evolve over the years and with the increasing use of multi-core

processors new versions or even new languages are bound to appear, sooner rather

than later.

An example - C program

A program has a carefully defined structure. It needs a start and end point and also

must itemize any special features such as libraries that may be needed. C programs

need to be written according to certain rules (syntax). These rules need to be followed

otherwise the program will probably fail to compile, or if it does compile, it may do

the wrong thing. A very basic program looks like :
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Example 1.1

#include #include

int main()

{printf("This is an example of a C program ");getch();return 0;

}

The line #include identifies the "header" file stdio.h which ensures that the

standard I/O library is included in the program, providing standard C input/output

facilities. The conio.h header allows various console I/O functions to be used. These

include the key read function 'getch()' - in this program it is there to stop the programso you can read the output, otherwise it would just flash by too quickly. This program

starts at 'main() { ' and ends at the last '}' .

So we have seen that a program runs sequentially, beginning at main() and finishing

at the last brace (}). This is not the end of the story by any means, software is useful

because it can make decisions and it can loop. A program can test inputs and act

accordingly, if the input is wrong then remedial action can be take. Such actions are

difficult to implement in pure hardware and any such solution is likely to lack

flexibility. Consider :

Example 1.2

#include #include int main()

{char ch;

printf("Enter a number from 1 to 4 \n");

ch = getch();if(ch< '1' || ch > '4') // is it < '1' OR > '4'?{

printf("You pressed the wrong key \n");}else{

printf("You pressed %c ",ch);}

getch();return 0;

}


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This program reads a key in using getchar() and then tests the value to see if it is less

than 1 or greater 4, in terms of the 8-bit ASCII value read from the keyboard. Note -

the logical OR operation is denoted by || in C. The %c entry in a printf() refers to

the character variable 'ch' declared in the program. So, the input is wrong if it is less

than '1' or greater than '4', otherwise it is correct and printed out.

Now try:-

Example 1.3

#include #include

int main(){

char ch;printf("Enter a number from 1 to 4 \n");ch = getch();while (ch< '1' || ch > '4'){

printf("You pressed the wrong key \n");ch = getch();

}printf("You pressed %c ",ch);

getch();return 0;}

Software can loop, using a while statement the program is now locked in a loop until

a correct entry is made. Note that the key is read before the loop (once) and then in

the loop, after the test, so that it tests the new key each time. Without that it would

test the original key which would be incorrect.

We can break out of the program using:-

if(ch=='q')

Exercise 1.1

Try changing the test range so that another number range is accepted. The try a

character range, say 0 to z. What can you tell from this about the ASCII character

set? Look at the full table on http://www.asciitable.com/.


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{return 0;}

We can now look a bit further at the keyboard itself and see what information it

provides for a computer system to respond to. If you look at the ASCII code table

mentioned earlier you will see that not all the keys on your keyboard are present. The

keyboard logic plays a clever trick and sends two characters for those keys, the first is

an 'escape' code (sometimes a zero byte) followed by a familiar character. This pair

represents the key e.g. is represented by 00 3b in hexadecimal (null, ; ).

Example 1.4

#include #include int main()

{char ch;

printf("Enter any key \n");ch = getch();while (ch != 'q')

{printf("You pressed the %c key - %x in hex \n",ch,ch);ch = getch();

}printf("Goodbye - hit any key to close");getch();return 0;

}

In printf() we can show the hexadecimal value of a variable with %x, note that the %

entries in the text line are matched by a list of the appropriate variables after the text

quotes have closed. Text is always shown in double quotes - "this is a text string", and

Exercise 1.2

Try putting this into the program to see if the program can be made to quit on 'q'.

Exercise 1.3

Run the program below and examine the values of keys. You should become

familiar with values for , 0-9 and the start of the upper and lower case

alphabet. You should try combinations such as c, and compare the

results with the ASCII table.


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a single character is shown in single quotes - 'q', The difference? A text string has an

extra byte on the end (null) to indicate that the end has been reached - corrupt that

and you are in trouble!

Hint: Consider using an exclusive OR operation, enter a key variable at the start

and then Exclusive OR the character with the key using ch^key. It works sometimes.

(Bit-wise operations in C are & = AND, | = OR, ^ = Exclusive OR and ~ = invert. Do

not confuse these with LOGICAL operations using && and || as in while (ch< '1' ||ch > '4')).

Exercise 1.4

i) Write a program that writes each character to the screen as typed until is

pressed. Remember = 00 3b, so just look for the null (00).

ii) Modify this program so that the text is printed in an encoded format. Can you

think of a way to do this so that the text can be reentered to recover what was

pressed. Like an Enigma machine!


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SECTION 2 - Program Structure

It is possible to write computer software that works but is both unreadable and

virtually impossible to modify. Software needs to have a structure so that it can easilybe understood by others and has a form of logic that means that it will meet any

situation that arises, not just the input that was planned but any input that might

occur. Quite a few software applications can be implemented as state machines. That

is, they move through a series of states as the application progresses. This often

applies to parts of an application as well, such as opening up a communication link.

If we consider an ATM application where the machine waits for a card, then for a PIN

number followed by a service selection, then we can divide it up into states:-

State Activity Input

0 Wait for card c and 0000-9999(PIN)

1 Enter service request A,W or R

2 Show balance

3 Request cash

4 Print statement

9 Eject Card

The 9th state leaves room for others to be added, this can be implemented using the

'switch' statement C where the variable controlling the flow of the logic is used to

select the appropriate 'case'. This is a common technique in engineering applicationsin a wide range of languages. Note that the state variable "state" is initialized to zero

so that we start with requesting a debit card.

Example 2.1

#include

#include #include

int state=0;

/*State variable*/char in;

int main()

{

while(1){

/*Tells you what state it is inprintf("State = %d\n",state);*/

switch(state)

{


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case 0:printf("Enter card - \n"); /* enter 'c' to represent the card input */

in=getch();

if (in== 'c')

{

printf("Enter PIN\n");getch();putch('*');

getch();

putch('*');getch();

putch('*');getch();

putch('*');

printf("PIN OK\n\n\n");state = 1;

/*These follow so they are only printed once, the state now changes*/printf("Select option\n");

printf("Account Balance - \n");

printf("Withdraw Cash - \n");printf("Request Printed Statement - \n");

}break;

case 1:

/*select user interface option*/in=getch();

if(in=='A'){ state = 2;}

if(in=='W')

{ state = 3;}if(in=='R')

{ state = 4;}break;

case 2:printf("Your account balance = %d.42\n",rand()/100); /*pseudo random amount*/

/* getchar();*/

state=9;break;

case 3:

printf("Please enter an amount - in ten pound steps\n"); /*no more steps here*/getchar();

state=9;

break;

case 4:printf("Please take your statement\n"); /*no more steps here*/

getchar();state=9;break;


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Now, if you have a program that compiles, and runs, think about the way it operates.

the PIN feature is meant to give 10,000 options for getting the number right and the

system detects multiple trys, eventually retaining the card. However, our model has a

logical flaw, you can derive the PIN after 10+10+10+10 trys instead of 10x10x10x10.

That is because it ejects after a single incorrect digit has been pressed. The sequence

to extract this PIN would be:

0 -> (eject card)

1 * (correct 1st digit)0 -> (eject)

1 -> (eject)

2 * (correct 2nd digit)

0 ->

1 ->

2 ->

3 * (correct 3rd digit)

0 ->

1 ->

2 ->

3 ->

4 * (correct 4th digit)

So after 14 attempts, the PIN is revealed. To correct this feature the PIN must be

loaded completely before checking, putting the digits into an empty array:

char buf[4]; /*Empty character array */

We can use this array as:

for(loopcount=0;loopcount


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Debugging your program

Once you have a program that will compile, key to open the debug window.

Move the cursor to a line at the start of the program and use Ctrl F4 (run to cursor)

Now you can step the program - and/or set a watch on a variable e.g.

'loopcount'.

As you step over a getch() you must click on the DOS window prompt so that the

character can be entered (only in this window).

Experiment with break points, run the code normally after clicking on a line in the

code so that it shows highlighted in red.

Conclusions : The code might compile and run but it might not be logically correct.

Always examine the specification carefully and identify any likely problems. These

can be corrected by adding additional features, if it all works, no one will commenton the change, they will not want any specification error being pointed out!

Exercise 2.2

Can you put these routines into your code and verify that it works as predicted.


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SECTION 3 - Graphics

In order for a program to be compiled with various libraries and other code that may

be needed, the user needs to provide a lot of information. This can be quite tiresometo key in every time and it is easy to make mistakes. One early option was to record

the complex command line in text file and provide that as part of a "batch file". This

technique is still used in some operating environments. If you have a development

environment like Dev Cpp then you can create a project file and set up the right

parameters in that. Then it is quite simple case of compiling as before. To use a

simple form of graphics with Dev Cpp, it is necessary to bring in the Borland

Graphical Interface library that has been ported to this environment and is supported

by the guys at the University of Colorado, on-line documentation is to be found at:

http://www.cs.colorado.edu/~main/bgi/doc/

Example 3.1

#include #include

#include

int main()

{float offset;

int i,x1,y1;initwindow(600,600);setfillstyle(1,YELLOW);

fillellipse(300,300,30,30);getchar();

}


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Example 3.3

#include

#include

int main()

{int i,x1,y1;

x1 = 300;

y1 = 300;initwindow(600,600);

setfillstyle(1,YELLOW);setcolor(BLACK); /*SET RIM OF CIRCLE TO BLACK */

for(i=0;i


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Exercise 3.2

If we want to bounce the disc off of the edge, we need to reverse the increment

of x, so that it moves back to the left. If we replace thefor (i=0;i


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SECTION 4 - Using Maths functions

Example 4.1#include

#include #include

int main()

{float offset;

int i,x1,y1;initwindow(900,900);

setcolor(BLACK);

while(1){

setfillstyle(1,YELLOW);//calculate moon position x1 has bigger offset so orbit is elipse

x1=(sin(offset)*200)+400;

y1=(cos(offset)*100)+400;//draw moon

fillellipse(x1,y1,15,15);

//draw planet

setfillstyle(1,RED);fillellipse (400,400,60,65);

//blank moon after delayfor(i=0;i


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Note on collisions:

We can use Pythagoras' theorem to find the distance between two objects.

[x1,y1]

Distance y1-y2

x1-x2

[x2,y2]

2 2 2Distance = (x1-x2) + (y1-y2)

if((int)sqrt((double)((x1-x2)*(x1-x2))+ ((y1-y2)*(y1-y2)))


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SECTION 5 - Functions, Structures and Objects

Functions

We have already used predefined functions like printf(). It is obvious they are a useful

way of carrying out operations that would otherwise have to be implemented with

blocks of code that would reoccur throughout the program. We can create our own

functions in one of two different ways. If we define our function after the main()

block, then a 'prototype' of the function (consisting of its header line terminated with

a semicolon (;), is needed before main. Otherwise, defining a function before main()

means that no prototype is needed:

Example 5.1#include void tick(); /*prototype for function tick */

void tock() /*function defined ahead of main, no need for prototype*/

{printf("TOCK\n");

}int main()

{

while(1)

{tick(); /*function calls */tock();

}

}void tick() /*definition of function tick */

{printf("TICK\n");

}

We can send various data items to a function including pointers to data but a function

only returns a single item as in:

ch= getch();

(You can tell its a function by the brackets.) ch=key; is not a function call!


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Structures

It is very useful to be able to group related item of data in a structure. This might be a

record to be written to a file or the information relating to some kind of item in the

code. The structure below is a descriptor of a data set that a graphic object needs to

operate. It will not exist as data until it is declared.

struct BUTTON {int x;

int y;

int on_color;int off_color;

int state;int buffer[2000];

};

struct LIGHT {int x;

int y;


int state;};

The complete program looks like :-

#include

#include

#define ON 1

#define OFF 0

struct BUTTON {int x;

int y;

int on_color;

int off_color;int state;

int buffer[2000];

};

struct LIGHT {

int x;int y;


int state;};


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void initbutton(BUTTON *button_str,int xpos,int ypos,int on,int off){

button_str->x=xpos;button_str->y=ypos;

button_str->on_color=on;

button_str->off_color=off;

button_str->state=OFF;

}

void initlight(LIGHT *light_str,int xpos,int ypos,int on,int off){

light_str->x=xpos;light_str->y=ypos;

light_str->on_color=on;

light_str->off_color=off;

}void drawlight(LIGHT *light_str)

{

setfillstyle(1,LIGHTGRAY);fillellipse(light_str->x,light_str->y,12,13);

if(light_str->state==ON){

setfillstyle(1,light_str->on_color);

}else

{setfillstyle(1,light_str->off_color);

}

fillellipse(light_str->x,light_str->y,10,10);setfillstyle(1,LIGHTGRAY);

bar(light_str->x-4,light_str->y-4,light_str->x+2,light_str->y-2);

}

void setlight(LIGHT *light_str,int state){

if(state >=0)

{ light_str->state =state;

drawlight(light_str);}

}int drawbutton(BUTTON *button_str)

{

setfillstyle(1,LIGHTGRAY);bar(button_str->x-22,button_str->y-22,button_str->x+22,button_str->y+22);

setfillstyle(1,WHITE);bar(button_str->x-26,button_str->y-26,button_str->x+26,button_str->y-23);

bar(button_str->x-26,button_str->y-26,button_str->x-23,button_str->y+26);setfillstyle(1,DARKGRAY);bar(button_str->x-26,button_str->y+23,button_str->x+26,button_str->y+26);


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initbutton(&button3, 300,200,BLACK,YELLOW);

initlight(&light1, 100,250,YELLOW,GREEN);initlight(&light2, 200,250,BLACK,RED);

initlight(&light3, 300,250,WHITE,BLUE);

drawbutton(&button1);drawbutton(&button2);drawbutton(&button3);

drawlight(&light1);drawlight(&light2);

drawlight(&light3);

while(!kbhit())

{s =getbutton(&button1);

setlight(&light1,s);s =getbutton(&button2);

setlight(&light2,s);

s =getbutton(&button3);setlight(&light3,s);

}closegraph();

return 0;

}

Compile this program using a project file as before.

This can be run to produce this result:

This program runs in a continuous loop, left click on a button to see its operation.


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The initialization routines simply load the structures with the given variables.

void initbutton(BUTTON *button_str,int xpos,int ypos,int on,int off){

button_str->x=xpos;button_str->y=ypos;

button_str->on_color=on;

button_str->off_color=off;button_str->state=OFF;

}void initlight(LIGHT *light_str,int xpos,int ypos,int on,int off)

{

light_str->x=xpos;light_str->y=ypos;

light_str->on_color=on;

light_str->off_color=off;}

void setlight(LIGHT *light_str,int state){

if(state >=0)

{light_str->state =state;

drawlight(light_str);}

}

The calling routine sends the address of the structure descriptor to the initializerwhich is then used to point to the structure elements.

This shows that the structures and the code routines are closely related and there is

likely to be some private functions that these use that the user would not normally

access.

Once you have built the structure you will have to create an instance of it, as in:-

BALL ball1; /*declaring a ball known as ball1*/

Now you need a function to initialize the ball, giving the address of ball1 (&ball1) tothe function, as well as its initial position and its colour. See above.

Exercise 5.1

Go back to the "bouncing ball" program and edit it, creating a structure for the "ball"

giving its position, colour, radius and direction.


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File Handling

Files are handled using a file pointer of type FILE. This creates a structure containing

details of the file including a link to the file control block. A byte counter is increased

with every access and can be reset using rewind(). Program below opens a file

"test.txt" (in your current working directory) which holds :-

jack

100

It amends the file with new data, in the same directory. For other pathsfopen uses \\as the first \ is an escape character as in \n. (newline)

You can usefprintfandfscanfin the same way that printf and scanf are used

except that the syntax would be as fprintf(out,"%s\n%s\n",name,score);

where out is a file pointer.FILE *in creates a pointer to a type FILE. From then on'in'refers to the pointer, which will be set to NULL if the file does not exist.

#include int main(void)

{

char newname[] = "john"; char newscore[] = "123";

char oldname[40];char oldscore[4];

FILE *in; /*File pointer */

if ((in = fopen("test.txt", "r+"))== NULL){

fprintf(stderr, "Cannot open input file.\n");

Exercise 5.2

Can you now modify the rest of the program to use the fields in the structure, so thatx1becomesball1.x1. This is a way accessing the field within a structure which

declared locally. Make sure that it runs like the original. Keep this program safe, you

will need need it later.

Exercise 5.3

This program can be altered to create a file using "w+" if it does not already exist, seeif you can do it.


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getchar();return 0;

}fscanf(in,"%s%s",oldname,oldscore);

rewind(in);

printf("Original file holds : %s %s",oldname,oldscore);

fprintf(in,"%s\n%s\n",newname,newscore);rewind(in);fscanf(in,"%s%s",oldname,oldscore);

rewind(in);

printf("\nNew file holds : %s %s",oldname,oldscore);getchar();

fclose(in);printf("\nOK \n");

getchar();

return 0;}

else

{ if ((in = fopen("test.txt", "w+"))== NULL){

fprintf(stderr, "Cannot open input file.\n");

getchar();return 0;

}

From then, its business as before:

fprintf(in,"%s\n%s\n",newname,newscore); /*write data to file*/

Exercise 5.4

How to change it:

We need to reverse the logic on the line that opens the file, so that if it exists, it is

read (fscanf) and the contents printed out (printf). to do this we need to change this

line to:if ((in = fopen("test.txt", "r+"))!= NULL)notice the change?

Now we can follow that with:

{ fscanf(in,"%s%s",oldname,oldscore);rewind(in);

printf("Original file holds : %s %s",oldname,oldscore); }

If thefopen returns a NULL it means that there is no such file and we have to create

one using "w+". So, using an 'else' we can take the reverse logic and try and open a

file of that name for writing:


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rewind(in); /*go back to start*/fscanf(in,"%s%s",oldname,oldscore); /* Read (new) data */

rewind(in);printf("\nNew file holds : %s %s",oldname,oldscore);

C++ Objects

This leads use to the basic concept of objects as used in C++, Java, C# and whatever

else comes next. The program below is in C++. Try it out. Notice thatset_values isaccessed as rect.set_values, as a function once it has been declared, just like

accessing the data in a C structure. In this case it is also set as public within the classCRectangle, making it accessible.

Example 5.2// C++ classes example from http://www.cplusplus.com/doc/tutorial/classes/

#include using namespace std;

class CRectangle {int x, y;

public:

void set_values (int,int);int area () {return (x*y);}

};

void CRectangle::set_values (int a, int b) {

x = a;y = b;

}

int main () {

CRectangle rect;rect.set_values (3,4);

cout


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definition. For example, in the function set_values() of the previous code, we have been able

to use the variables x and y, which are private members of class CRectangle, which means they

are only accessible from other members of their class. "

So you can see, C++ is not easy to learn from scratch, a good knowledge of C helps a

great deal. Java is slightly less complex than C++. C# is tied to Microsoft and is notportable across other operating systems.


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Section 6 - Multitasking

It may come as a surprise but there are far more microprocessors in your life than the

few obvious ones you see every day. You may think that Windows is the onlycomputer operating system around but every phone has a specialized operating

system, others, called Real Time Operating Systems are to be found providing your

power, water, food, transport and health care. These systems have to stay live day

after day, year after year. There is no rebooting an atomic power station or an

intensive care monitor, they just have to work. These systems share a common

feature, they run code as a set of cooperating tasks that time share the central

processor. This multi-tasking allows tasks with a higher priority to get a larger share

of the CPU's time. They can also communicate and synchronize through a variety of

mechanisms including the one we are going to see here, the pipeline.

InP

Pipe Buffer

OutP Pointers wrapround to start

A pipe can be used to link two tasks so that neither has to wait when data is

transferred, unless it is full or empty.

Multitasking

In an RTOS there are multiple tasks running, with different priorities and fast

response mechanisms are provided for interrupts and other events. The task

scheduling is carried by a scheduler that is driven by a timer interrupt. Multitasking

also takes place in non-real time operating systems such as Windows and Linux.

A way of achieving multi-tasking without a scheduler is known as cooperative

multitasking. This technique can be used to divide an application into tasks, where

some tasks have lower priority and run less often. It can even be applied to simple

microcontrollers such as the PIC 16F8x devices. Here an application is split intomajor functions, representing the tasks. These are run in a switch-case architecture

and can be selected according to priority. The major difficulty is that tasks have to


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hand control back to the scheduling routine, if they do not, the whole application

comes to a halt. (Remember Windows 95!).

/*A demonstration of Cooperative Multitasking

each task is run in turn, a delay loop slows the system down sothat the user can interact. Priorities are applied based on the loop counter

the lower the value the more likely count%(modulus)priority will produce a zero*/

// This is needed for DevC++, comment out for MPLAB

#include

//Comment out for DevC++, leave in for MPLAB

/*#if defined(__PCM__)

#include #fuses HS,NOWDT,NOPROTECT

#use delay(clock=20000000)

#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7) // Jumpers: 8 to 11, 7 to 1*/

void task1 ();void task2 ();

void task3 ();struct Task_st

{

int id;int pr;

int en;};

struct Task_st Tsks[3];

void task1(){

printf("Task 1 running\n");

return;}

void task2(){

printf("Task 2 running\n");return;

}

void task3(){

printf("Task 3 running\n");return;

}int main(){


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int state,j,counter=0;//Creating task table

Tsks[0].id=1;Tsks[1].id=2;

Tsks[2].id=3;

//Creating priority list

Tsks[0].pr=1;Tsks[1].pr=1;Tsks[2].pr=1;

//Enable Tasks

Tsks[0].en=1;Tsks[1].en=1;

Tsks[2].en=1;

while(1){

counter++;// Scheduler routine

for(state=0;state


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There are a number of other mechanisms commonly used in RTOSs, passing data by

reference, setting flags to indicate events and posting data in "mailboxes" are just

some of them. The use of multi-core processors has brought on a new revolution in

concurrent programming and C++ is now being used in various ways to support the

programmer -www.openmp.org and Intel have now acquired a software house

dedicated to this problem. RTOS suppliers provide tools that support multitaskingand more importantly, the debugging process in this environment :

http://www.ghs.com/products/TI_davinci_development.html

http://www.qnx.com/news/pr_3361_1.html

http://www.embeddeddesignindia.co.in/ART_8800535482_2800002_TA_3d44a76

2.HTM

Exercise 6.2

Write a single paragraph summary of the situation for RTOSs in multi-core

systems. (max 200 words)


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SECTION 7 : The Pin Ball Assignment

This assignment requires you develop a game program that displays as Pin Ball

game. Using the skills that you have already acquired, and the code examples,

develop a program that has the following characteristics:

a) The ball bounces off all sides of the game area, displaying some random

characteristics.

b) The ball bounces off randomly placed pillars on the screen.

c) The game finishes when the ball "falls" into a "hole". The score of hits on the

pillars at that stage is shown. If it is higher than a recorded value then the user is

invited to enter a name, and the new top score is recorded.

d) Paddles at the base of the screen can be activated using left and right mouse keys.

(see graphics.h and the "colorado" website.

These add momentum to the ball (speed it up).

e) The ball loses momentum over time and slows down, losing height on the playing

area, unless accelerated by the paddles.

f) If the ball loses all height, it rolls off the bottom of the game area and the game isover.

These must be written up in a report and the final program demonstrated before the

last laboratory session ends. Late work will be penalized. Do NOT copy work from

others, duplicate work will result in penalties for all parties.

Marks 60% [ 10% for each section a)-f) ]

c programming by example

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