HW 4

Problem 1

Bouncing Ball

 

1. Compile and run the following code.

* Put Console.c and Console.h into the current directory, and run the following commands:

gcc [file name].c Console.c -D_WINDOWS // on Windows

gcc [file name].c Console.c -D_MAC // on MacOS

2. Modify the code so that the ball bounces like the video below

 

skeleton code

#include <stdio.h>

#include "Console.h"

int main()
{
    int screen_width = getWindowWidth();       // get width of current console window
    int screen_height = getWindowHeight() - 3;      // get width of current console window
    int x = screen_width / 2, y = screen_height / 2;           // set initial coordinate by center of the screen
    int dx = 1, dy = 1;
    int key = 0;

    clrscr();               // clear screen (defined in Console.c)
    gotoxy(1, screen_height + 1);
    printf("screen size = %d x %d. Press ESC to fisnish.\n", screen_width, screen_height);
    
    while(key != 27){           // the ASCII code of ESC is 27.
        // save previous coordinate
        int oldx = x;
        int oldy = y;

        // move the coordinate of the ball
        y += dy;
        if(y > screen_height)          // if the ball reaches the bottom, restart from the top
            y = 1;

        // erase previous coordinate
        gotoxy(oldx, oldy);
        printf(" ");

        // draw star at the new object
        gotoxy(x, y);
        printf("*");

        // move the cursor to (1, 1) so that it does not blink
        gotoxy(1, 1);

        // flush screen (display all content in the output buffer and flush it)
        // this is to display all messages immediately.
        fflush(stdout);

        // the following routine detects and reads a key press. this is to stop when ESC key is pressed.
        if(kbhit())
            key = getch();

        // delay for 50 ms
        MySleep(50); // defined in Console.c   
    }

    clrscr();
    gotoxy(1, 1);
    printf("Bye!\n");

    return 0;
}

revised code

#include <stdio.h>

#include "Console.h"

int main()
{
    int screen_width = getWindowWidth(); // get width of current console window
    int screen_height = getWindowHeight() - 3; // get height of current console window
    int x = screen_width / 2, y = screen_height / 2; // set initial coordinate by center of the screen
    int dx = 1, dy = 1;
    int key = 0;

    clrscr(); // clear screen (defined in Console.c)
    gotoxy(1, screen_height + 1); 
    printf("screen size = %d x %d. Press ESC to finish.\n", screen_width, screen_height);
    
    while(key != 27){           // the ASCII code of ESC is 27.
        // save previous coordinate
        int oldx = x;
        int oldy = y;

        // move the x and y coordinate
        x += dx;
        y += dy;

        if(y<0 || y > screen_height) // if 'y' is out of the range of the minimum or maximum y coordinate of the screen,
            dy*=-1; // multiply 'dy' by -1 to put the y coordinate within the range of the screen
        if(x<0 || x > screen_width) 
            dx*=-1;
        
        clrscr(); //clean screen 

        // draw star at the new object
        gotoxy(x, y);
        printf("*");

        // move the cursor to (1, 1) so that it does not blink
        gotoxy(1, 1);

        // flush screen (display all content in the output buffer and flush it)
        // this is to display all messages immediately.
        fflush(stdout);

        // the following routine detects and reads a key press. this is to stop when ESC key is pressed.
        if(kbhit())
            key = getch();

        // delay for 50 ms
        MySleep(50);      // defined in Console.c   
    }

    clrscr();
    gotoxy(1, 1);
    printf("Bye!\n");

    return 0;
}

 

Problem 2

Center Editor

 

1. Compile and run the following code.

* Put Console.c and Console.h into the current directory, and run the following commands:

gcc [file name].c Console.c -D_WINDOWS // on Windows

gcc [file name].c Console.c -D_MAC // on MacOS

2. Complete the code so that it can run as the video below

 

 

 

skeleton code

#include <stdio.h>
#include <string.h>

#include "Console.h"

void PrintCenter(char text[], int cx, int cy);
// Displays a text at the center of the screen

void Erase(int len);
// Erases a text from the screen given its length

void EraseCenter(int len, int cx, int cy);
// Erases the previous message at the center of the screen given the length of the previous message

int main()
{
    int screen_width = getWindowWidth();            // get width of current console window
    int screen_height = getWindowHeight() - 3;      // get width of current console window
    int cx = screen_width / 2, cy = screen_height / 2;   // center of the screen

    char text[256] = "";
    int len = 0;				// the length of text

    clrscr();
    gotoxy(1, 1);
    printf("Press ESC to quit.\n");

    char key = 0;
    while(key != 27){
        int oldlen = len;			// save the length of the current text

        key = getch();				// reads a key from the user
        switch(key){
            case 27:    // ESC key
            	// if key == ESC, do nothing
                break;

            case 8:     // backspace key
                // TO DO: erase the last character of text and decrease len.
                //      Then, reprint the text at the center of the screen

                break;

            case 13:     // Enter key
				// TO DO: print current text at (1, 2). (erase previous text at (1, 2))
                
                
                // TO DO: clear text (fill text[0] by zero), and reset len to zero
                

                // TO DO: Erase the center text


                break;

            default:	// all other keys
                // TO DO: append key at the end of text, and increase len
                

                // TO DO: display new text at the center of the screen


                break;
        }               
    }

    // print a goodbye message at (1, 3)
    gotoxy(1, 3);
    printf("Bye!\n");
    
    return 0;
}

void PrintCenter(char text[], int cx, int cy)
// Displays a text at the center of the screen
{
    int len = strlen(text);         // returns the length of text. declared in string.h
    gotoxy(cx - len / 2, cy);
    printf("%s", text);
}

void Erase(int len)
// Erases a text from the screen given its length
{
    // TO DO: print space character len times (use the for statement)

}

void EraseCenter(int len, int cx, int cy)
// Erases the previous message at the center of the screen given the length of the previous message
{
	// TO DO: implement this function
   
}

 

revised code

#include <stdio.h>
#include <string.h>

#include "Console.h"

void PrintCenter(char text[], int cx, int cy);
// Displays a text at the center of the screen

void Erase(int len);
// Erases a text from the screen given its length

void EraseCenter(int len, int cx, int cy);
// Erases the previous message at the center of the screen given the length of the previous message

int main()
{
    int screen_width = getWindowWidth(); // get width of current console window
    int screen_height = getWindowHeight() - 3; // get width of current console window
    int cx = screen_width / 2, cy = screen_height / 2; // center of the screen

    char text[256] = "";
    int len = 0; // the length of text

    clrscr();
    gotoxy(1, 1);
    printf("Press ESC to quit.\n");

    char key = 0;
    while(key != 27){
        int oldlen = len; // save the length of the current text

        key = getch(); // reads a key from the user
        switch(key){
            case 27: // ESC key
            	// if key == ESC, do nothing
                break;

            case 8: // backspace key
                // TO DO: erase the last character of text and decrease len.
                // Then, reprint the text at the center of the screen
                text[oldlen-1]=0;
                oldlen-=1;
                EraseCenter(oldlen,cx,cy);
                PrintCenter(text, cx, cy);

                break;

            case 13: // Enter key
				// TO DO: print current text at (1, 2). (erase previous text at (1, 2))
                gotoxy(1,2);
                Erase(screen_width);
                gotoxy(1,2);
                printf("%s",text);
            
                // TO DO: clear text (fill text[0] by zero), and reset len to zero
                text[0]=0;
                len=0;

                // TO DO: Erase the center text
                EraseCenter(oldlen,cx,cy);

                break;

            default: // all other keys
                // TO DO: append key at the end of text, and increase len
                text[len]=(char)key;
                len+=1;
                text[len]=0;

                // TO DO: display new text at the center of the screen
                PrintCenter(text,cx,cy);

                break;
        }               
    }

    // print a goodbye message at (1, 3)
    gotoxy(1, 3);
    printf("Bye!\n");
    
    return 0;
}

void PrintCenter(char text[], int cx, int cy)
// Displays a text at the center of the screen
{
    int len = strlen(text); // returns the length of text. declared in string.h
    gotoxy(cx - len / 2, cy);
    printf("%s", text);
}

void Erase(int len)
// Erases a text from the screen given its length
{
    // TO DO: print space character len times (use the for statement)
    for(int i=0 ; i<len ; i++)
        printf(" ");
}

void EraseCenter(int len, int cx, int cy)
// Erases the previous message at the center of the screen given the length of the previous message
{
	// TO DO: implement this function
    char str[len];
    for(int i=0 ; i<len ; i++)
        str[i]=' ';
    str[len]=0;
    PrintCenter(str,cx,cy);
}