CSc 343
Computer Organization and Programming
Spring Quarter 1998
Programming Assignment #2 (Due: 13 May 1998, Wednesday)

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 two clocks (one for ATLANTA time and the other for another world city time) on the screen. When your program begins, the screen should be cleared, the following should be displayed, and the two clocks should keep advancing (at the rate of approximately 1 second per second).

The clocks should have the following functionality:

1. Daylight Savings Time: When the user presses the d key, the ATLANTA TIME should toggle between EST (Eastern Standard Time) and DST (Daylight Savings Time). When the time is switched to DST, the ATLANTA time should be turned back 1 hour and the term DST should replace EST. Similarly, when the time is switched back to EST, the ATLANTA time should be turned forward by 1 hour and the term EST should replace DST.
2. World City Times: Your program should have the capability to display the times for the following cities.

   CITY       Difference with EST    Difference with DST
   -----------------------------------------------------
   Karachi          +9.00                   +9.00
   London           +4.30                   +5.30
   Madras           +9.30                  +10.30
   Paris            +5.30                   +5.30
   Phoenix          -2.00                   -2.00
   Singapore       +13.00                  +14.00
   Wichita          -1.00                   -1.00
   ----------------------------------------------------

   When the first letter of any of these cities is pressed on the keyboard, the second clock should switch to the time in that city and the clock should be appropriately labeled with the name of the city.
3. Set Time: When the user presses the t key, the user may set the ATLANTA time. 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 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 time setting, the t key may once again be pressed to return to the time display.

   Note that when the ATLANTA time is set, the times in the other cities are also changed appropriately.

4. Reset Time: When the user presses the r key, the ATLANTA time should be reset to AM 12:00 and the clock should start ticking immediately after the reset. Note that the other city times should also be reset under this option.
5. 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. 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.
3. 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.

4. 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.
5. Be careful not to display 12:00:00 as 00:00:00.
6. Be careful about midnight and noon transitions.

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