CSc 343 Computer Organization and Programming
Fall Quarter 1997
Programming Assignment #2 (Due: 31 October 1997, Friday)

Assignment Objectives: To gain experience with program control (procedures and jump instructions), screen processing in text mode, and simple keyboard processing.

Problem Description: Write an assembler program that will simulate an alarm clock on the screen. When your program begins, the screen should be cleared and the following should be displayed and the clock should keep advancing (at the rate of approximately 1 second per second).

The alarm clock should have the following functionality:

1. Alarm ON/OFF: When the user presses the o key, the alarm status should toggle between ON and OFF. You may assume that the alarm is OFF when your program begins. When the alarm is ON, the display should have an asterix after the time as follows:

   

2. Set Alarm Time: When the user presses the a key, the display should switch to the following:

   

   and the user should be allowed to use the up arrow and the down arrow keys to increase or decrease the hours or minutes setting of the alarm time. The user should be able to switch between setting hours and minutes by pressing the h or the m keys. To begin with, you may assume that the hour will be set with the arrow keys. Once the user is satisfied with the alarm setting, the a key may once again be pressed to return to the time display.

   IMPORTANT NOTE: While the alarm time is being set, the clock should keep running and not lose time! Also, while setting the alarm time, the time setting key t should be ignored. All other commands (the o, the r and the escape keys) should still be accepted and processed.

3. Set Time: When the user presses the t key, the user may set the time. The time is set in a similar fashion as the alarm setting (i.e. with the up arrow, down arrow, h and the m keys).

   IMPORTANT NOTE: While the time is being set, all other keys should be ignored. After the user is satisfied with the time setting, the t key may once again be pressed to return to the regular time display. Note that while setting the time, it does not make sense to keep running the clock!

4. Reset Time: When the user presses the r key, the time should be reset to AM 12:00:00 and the clock should start ticking immediately after the reset.
5. Sound Alarm: If the alarm status is ON and the alarm setting is the same as the time, the program should sound the alarm (send the BELL character 20 to 30 times to the screen).
6. Exit Program: The program should terminate when the escape key is pressed at any time except while setting the time.

Submission Instructions: Electronically submit clock.asm and clock.exe by the deadline and submit program listing of clock.asm.

Hints:

1. Start small. For example, you might first write a program that simply clears the screen and draws the box. Then, add the time to the box. Make the clock tick next. Then, start adding the functionality one at a time.
2. To introduce a 1 second delay, you may set up a separate procedure which has several nested loops. I set up one with 3 levels of nesting with the number of iterations being 10H, 100H and 100H for the outer, middle and inner loop respectively. You may experiment with these numbers to get a reasonable delay. It does not have to be exact one second!
3. You will need to make the cursor disappear (to avoid an annoying flicker). Use INT 10H, function 03H, to determine the top and bottom scan lines of the cursor. Save these in the data segment. Then use INT 10H, function 01H, to make the cursor invisible. Just before the program terminates, use the same interrupt to restore the cursor to its original size.
4. Some new DOS/BIOS services to use in this assignment (you will need some of the services used in Assignment 1 as well):

     INT 10H, Function 01H: Set Cursor Size
        Useful for changing the size of the cursor or making it disappear
        entirely. See Page 162 of the text for details. To make the
        cursor disappear, put 20H in CH before performing the interrupt.
   
     INT 16H, Function 11H: Determine if key pressed
        Useful to check if the user has pressed any key. See P 191 for details.
   
     INT 16H, Function 10H: Read key from keyboard
        Useful after we have determined that the user has pressed a key.

5. You will need to use the extended ASCII codes for the characters that will make up the box containing the time (see Page 171 of text). These are: CDH for Horizontal double line, BAH for Vertical double line, C9H for Top Left, C8H for Bottom Left, BBH for Top Right and BCH for Bottom Right.
6. Be careful not to display 12:00:00 as 00:00:00.
7. Be careful about midnight and noon transitions.