Description
Instructions For this assignment, you must write four programs in the assembly language you just started
learning. The four programs will be included in ONE file inside ONE project. These programs should be
implemented and tested using the Visual Studio IDE. For all these exercises, you cannot use built-in functions that
perform these operations. In case of a doubt, check with your instructor.
For this assignment, you will build your own byte input/output functions using basic character
input/output functions provided by the author of the textbook.
Objectives of this assignment:
• to build up your programming skills in the assembly language
• to get familiar with Visual Studio
• to stress on the fact that the memory (variables) ultimately are 0s and 1s
• to use some basic character input/output functions
• to build your own basic byte input/output functions.
• to distinguish between “numbers” and characters
Warning:
The executable you will build may get blocked by an Antivirus scanner on your system. In this case,
read this from the Textbook author: “Antivirus scanner software has improved greatly in recent years, and so have
the number of viruses (one website reports 50,000 at present). Because of this, your computer’s antivirus scanner may
report a false positive when you build your program, and refuse to let you run it. There are a few workarounds: (1) You
can add your project’s bin/debug folder into an exclusion list in your antivirus configuration. This is my preferred approach,
and it nearly always works. (2) You can suspend your realtime antivirus scanner software, but this will leave you open to
malware for a short time. If you choose this option, be sure to temporarily disconnect your computer from the Internet.
(3) You can send a copy of your program’s EXE file to the antivirus software vendor, labeling it as a false positive. The
virus scanner I use automatically uploads any questionable EXE file to their website and either quarantines or releases
the file within about 30 minutes.” I used the first workaround, i.e., I added my project’s /debug folder to the exclusion list
in my antivirus configuration.
Input/Output Built-in Functions Allowed:
The textbook author wrote some helpful functions. For this project, you can use only these two
functions:
1) ReadChar : this function will allow you to read a character from the keyboard and receive its ASCII
code in the register AL. This function is described in the textbook Page 165 (beginning/page).
2) WriteChar : this function will allow you to display on the console window (command window) a
character whose ASCII code is stored in the register AL. See in the textbook Page 169 (start/page).
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For this project, you must ultimately design and implement the code for these two functions:
1) WriteHexByte : this function will allow you to display on the console window (command window)
the hexadecimal number stored in the register AL. Note that for this project, you need only to write
the code. In a future assignment, you will organize it as a function (procedure that you can reuse).
2) ReadHexByte : this function will allow you to read an 8-bit hexadecimal integer from the keyboard
and receive it in the register AL.
Note that for this project, you need only to write the code for these two functions. In a future
assignment, you will organize them as functions (i.e., procedures that you can call).
Note: the four exercises must be included in ONE project using ONE assembly file. Just separate in the file the
exercises using clear comments.
Programming Exercise 1 (10 points):
The objective of this exercise is to write a program that converts a value v of a decimal digit d into the
ASCII code of the digit d. We assume that the register AL contains a value between 0 and 9. Therefore, AL will
contain the value of a decimal digit ‘0’ to ‘9’. You do not have to test AL for the range.
Your program 1) must store in the register DL the ASCII code of the character, and 2) must display the
character using the function WriteChar.
Example: If AL will contain the value 4. Your program 1) must store in DL the ASCII code of ‘4’, i.e. DLß34h,
and 2) must display the character 4 using the built-in function WriteChar.
To test our program, you must initialize AL to various values varying from 0 to 9 (e.g., MOV AL, 06h)
just before your instructions of the program you wrote.
Programming Exercise 2 (40 points): (Implementing WriteHexByte)
The objective of this exercise is to write a program that implements the function WriteHexByte to display in
hexadecimal on the console the byte contained in the register AL. We assume that AL contains a hexadecimal
number that uses only decimal digits (i.e. 0 to 9). Therefore, AL will contain a value such that both nibbles take
only the values from 0 to 9. For example, if AL = 94h = (1001 0100)2, then this content is valid because the
most significant nibble (1001)2 and the least significant nibble (0100)2 are in the range [0-9]. The value 5Ah is
invalid because the least significant nibble ((1010)2 = Ah) is not in the range [0-9]. Given a valid value in AL,
your program must :
1) store in the register DH the ASCII code of the most significant nibble
2) store in the register DL the ASCII code of the least significant nibble.
3) Display (using WriteChar) on the console the character stored in DH (recall that WriteChar uses
AL for the character to display)
4) Display (using WriteChar) on the console the character stored in DL
5) Display ‘h’ to indicate that the number is a hexadecimal number.
6) ‘Display’ the ‘line feed’ character (ASCII code is 0Ah) to go to the next line
7) ‘Display’ the ‘carriage’ character (ASCII code is 0Dh) to go to the next line
Displaying a ‘line feed’ and a ‘carriage return’ will produce a new line. Check what happens if you do not
display ‘line feed’ and/or a ‘carriage return’.
Example : If AL contains the number 94h, your program 1) must store 39h (ASCII code of the character ‘9’)
in DH , 2) must store 34h (ASCII code of the character ‘4’) in DL, 3) must display the characters ‘9’, ‘4’, ‘h’, ‘line
feed’, and ‘carriage return’. Recall that ‘line feed’ is ONE character whose ASCII code is 0Ah and ‘carriage
return is ONE character whose ASCII code is 0Dh
To test our program, you must initialize AL to various values varying from 00h to 99h (e.g., MOV AL, 47h)
just before your instructions of the program you wrote. Do NOT use hexadecimal digits.
Programming Exercise 3 (10 points):
The objective of this exercise is to write a program that will read a decimal digit d from the keyboard,
convert the ASCII code of a digit d into the value v of d, and store v in the register DL .
You must use the function ReadChar to input a decimal digit d from the keyboard. As described above,
the function ReadChar will return in the register AL the ASCII code of the decimal digit d. We assume that the
user will input ONLY decimal digits (‘0’ to ‘9’). Therefore, the register AL will contain the ASCII code of a
decimal digit ‘0’ to ‘9’, i.e., 30h to 39h. You do not have to test AL. Your program must store in the register DL
the value of the digit.
Example: If the user enters the digit ‘4’, AL will contain the ASCII code 34h. Your program must store in
DL the value of the digit ‘4’, i.e., the value 04h. Ultimately, DL ß 04h.
Programming Exercise 4 (40 points):
The objective is to write a program that implements the function ReadHexByte to input from the keyboard
a byte (i.e., two digits) and store it in the register AL. You must write the program to implement the function
ReadHexByte. In order to achieve this, you must read consecutively two decimal digits from the keyboard
(use ReadChar for each digit). We assume that the user will enter only TWO decimal digits (i.e. ‘0’ to ‘9’).
The first digit entered will be set as the most significant nibble of AL and the second digit entered will be set as
the least significant nibble of AL. Process appropriately the two characters and store in AL the value meant by
the user.
Example: suppose the user enters the digit ‘9’ followed by the digit ‘4’. This means that the user means the
byte 94h. Your program must ultimately store in AL the value 94h = (1001 0100)2. The digit ‘9’ ‘produced the
most significant nibble (1001)2 and the digit ‘4’ ‘produced the least significant nibble (0100)2.
What you need to turn in:
• Post on Canvas the following files:
1) Electronic copy of your report (standalone) as a word or PDF file.
2) The source code main.asm (standalone): this file will contain the four programs.
3) Your full project folder that will include your main.asm. This project folder must be named first
named m4-name where name is your last name. Do not have spaces in the file names. After you
correctly name the folder, zip it and post it on Canvas.
Your report must:
• State whether your code works (this should not take more than a sentence). Failing to make this
statement can be interpreted that your code does not work correctly and does not meet the
requirements
• Good writing and presentation are expected.
How this assignment will be graded:
1. The program compiles but does not produce any meaningful result (5%).
2. The program compiles and executes with major bugs (40% credit).
3. The program compiles and executes with minor bugs. The code is well designed and commented (90%
credit).
4. The program compiles and executes correctly without any apparent bugs. The code is well designed and
commented (100%).
5. If the instructor needs additional communications/actions to compile and execute your code, then a 30%
penalty will be applied.
6. If the turn-in instructions are not correctly followed, 10 points will be deducted.