LC3汇编模拟器代写：COMPSCI 210 Assignment 3

COMPSCI 210 Assignment 3

Due date: 21:00 29th May 2018 Total marks: 100

This assignment aims to give you some experience with C programming and to help you gain better understanding of the addressing mode of LC‐3.

Important Notes

 There are subtle differences between various C compilers. We will use the GNU compiler gcc on login.cs.auckland.ac.nz for marking. Therefore, you MUST ensure that your submissions compile and run on login.cs.auckland.ac.nz. Submissions that fail to compile or run on login.cs.auckland.ac.nz will attract NO marks.
 Markers will compile your program using command “gcc –o name name.c” where name.c is the name of the source code of your program, e.g. part1.c. That is, the markers will NOT use any compiler switches to supress the warning messages.
 Markers will use machine code that is different from the examples given in the specifications when testing your programs.
 The outputs of your programs will be checked by a program. Thus, your program’s outputs MUST be in the EXACTLY SAME FORMAT as shown in the example given in each part. You must make sure that the registers appear in the same order as shown in the example and there are no extra lines.
 The files containing the examples can be downloaded from Canvas and unpacked on server with the command below:
```
      o  tar xvf A3Examples.tar.gz
```
 As we need to return the assignment marks before the exam of this course, there is NO possibility to extend the deadline for this assignment.
Academic Honesty

Do NOT copy other people’s code (this includes the code that you find on the Internet).

We will use Stanford’s MOSS tool to check all submissions. The tool is very “smart”. Changing the names of the variables and shuffling the statements around will not fool the tool. In previous years, quite a few students had been caught by the tool; and, they were dealt with according to the university’s rules at https://www.auckland.ac.nz/en/about/learning‐and‐ teaching/policies‐guidelines‐and‐procedures/academic‐integrity‐info‐for‐students.html

In this assignment, you are required to write C programs to implement a LC‐3 simulator. That is, the programs will execute the binary code generated by LC‐3 assembler.

1

Part 1 (35 marks)

LC3Edit is used to write LC‐3 assembly programs. After a program is written, we use the LC‐3 assembler (i.e. the “TranslateAssemble” function in LC3Edit) to convert the assembly program into binary executable. The binary executable being generated by LC3Edit is named “file.obj” where “file” is the name of the assembly program (excluding the “.asm” suffix). In this specification, a “word” refers to a word in LC‐3. That is, a word consists of two bytes. The structure of the “file.obj” is as below:

 The first word (i.e. the first two bytes) is the starting address of the program.
 The subsequent words correspond to the instructions in the assembly program and the
contents of the memory locations reserved for the program using various LC‐3 directives.
 In LC‐3, data are stored in Big‐endian format (refer to https://en.wikipedia.org/wiki/Endianness to learn more about Big‐endian format). For example, if byte 0x12 in word 0x1234 is stored at address 0x3000, byte 0x34 is stored at address 0x3001. This means, when you read a sequence of bytes from the executable of
an LC‐3 assembly program from a file, the most significant bit of each word is read first. In this part of the assignment, you are required to write a C program to display each word in the “.obj” file of a program in hexadecimal form. That is, the C program should display each binary number stored in the “.obj” file in it corresponding hexadecimal form.
-  Name the C program as “part1.c”.
-  The name of the “.obj” file (the name of the file INCLUDES the “.obj” suffix) must be
  given as a command line argument. The number of instructions in the file is NOT
  
  limited.
-  In the output, each line shows the contents of one word.
-  The value of each word must have a “0x” prefix.
-  The letter digits “a” to “f” must be shown as lowercase letters.
  Here is an example of the execution of the program. In this example, the LC‐3 assembly program is as below. The name of the executable of the assembly program is “p1.obj” (markers will probably use a file with a different name and different contents).

.ORIG X4500
LD R0, A
LEA R1, B
LDI R2, C
AND R3, R0, R1 AND R3, R1, #0 NOT R4, R3

ADD R4, R4, #1 BRp F
ADD R3, R3, #1

F HALT

A .FILL X560A
B .FILL X4507
C .FILL X4501

.END

The execution of the program is shown below. In this example, the name of the file containing the machine instructions is p1.obj (NOTE: “p1.obj” is the exact name of the file. That is, the file name does NOT have a ‘.txt’ suffix.). The command line argument is marked in red.

    $ ./part1 p1.obj
    0x4500
    0x2009
    0xe209

Part 2 (46 marks)

In this part, you are required to write a C program to implement a LC‐3 simulator that is capable of executing instruction “LD”.

 Name the C program as “part2.c”.
 The name of the “.obj” file (the name of the file INCLUDES the “.obj” suffix) must be
given as a command line argument. The number of instructions in the file is NOT

limited.
 The state of the simulator consists of the contents of the 8 general purpose registers (i.e.
R0 to R7), the value of the program counter (i.e. PC), the contents of the instruction

register (i.e. IR), and the value of the condition code (i.e. CC).
 The values in R0 to R7, PC and IR should be shown as hexadecimal value. The value of CC
is either N, Z or P.
 Before the simulator starts executing a program, it should first display the initial state of
the LC‐3 machine. In the initial state, R0 to R7 and IR should all be 0; PC should be the

starting address of the program to be executed; and CC should be set to Z.
 When displaying the value of R0 to R7, PC, IR and CC, a tab character (denoted as “\t” in
C) is used to separate the name of the register and the value of the register. 3

 Each hexadecimal value must have a “0x” prefix. The letter digits “a” to “f” must be shown as lowercase letters.
 After showing the initial state, the simulator should execute each instruction except the “HALT” pseudo instruction in the “.obj” file. For this part, the simulator should display the hexadecimal code of each LD instruction that has been executed and the state of the LC‐3 machine after each LD instruction is executed. The hexadecimal code of an instruction is the hexadecimal form of the 16 bits used to represent the instruction. The hexadecimal code of each LD instruction should be preceded with “after executing instruction\t” (where \t denotes a tab character) and “0x”.
 The simulator should output a line consisting of 18 “=” after displaying the state of the LC‐3 machine.
 When the execution reaches the “HALT” instruction, the simulator terminates.
Here is an example of the execution of the program. In this example, the LC‐3 assembly program is as below. The name of the executable of the assembly program is “p2.obj” (NOTE: “p2.obj” is the exact name of the file. That is, the file name does NOT have a ‘.txt’ suffix). Markers will probably use a file with a different name and different contents.

.ORIG X4500

LD R0, A F HALT

A .FILL X560A
B .FILL X4507
C .FILL X4501
.END

The execution of the program is shown below. The command line argument is marked in red.

$ ./part2 p2.obj
Initial state

R0 0x0000
R1 0x0000
R2 0x0000
R3 0x0000
R4 0x0000
R5 0x0000
R6 0x0000
R7 0x0000

PC      0x4500
IR      0x0000
CC      Z
==================
after executing instruction

R0 0x560a
R1 0x0000
R2 0x0000
R3 0x0000
R4 0x0000
R5 0x0000
R6 0x0000
R7 0x0000

PC      0x4501
IR      0x2001
CC      P

0x2001

       ==================

Part 3 (3 marks)

This part is based on Part 2.

 Name this program as part3.c
 Expand the functionality of the simulator in part 2 to allow the simulator to execute
instruction “LEA”.
 For this part, the simulator should display the hexadecimal code of each LEA instruction
that has been executed and the state of the LC‐3 machine after each LEA instruction is executed. The hexadecimal code of each LEA instruction should be preceded with “after executing instruction\t” (where \t denotes a tab character) and “0x”.
 The simulator should output a line consisting of 18 “=” after displaying the state of the LC‐3 machine.
Here is an example of the execution of the program. In this example, the LC‐3 assembly program is as below. The name of the executable of the assembly program is “p3.obj” (NOTE: “p3.obj” is the exact name of the file. That is, the file name does NOT have a ‘.txt’ suffix.). Markers will probably use a file with a different name and different contents.

.ORIG X4500

LD R0, A LEA R1, B

F HALT

A .FILL
B .FILL
C .FILL
.END

The execution of the program is shown below. The command line argument is marked in red.

X560A
X4507
X4501

    $ ./part3 p3.obj
    after executing instruction

R0 0x560a
R1 0x4504
R2 0x0000
R3 0x0000
R4 0x0000
R5 0x0000
R6 0x0000
R7 0x0000

    PC      0x4502
    IR      0xe202
    CC      P
    ==================

Part 4 (3 marks)

This part is based on Part 3.

0xe202

 Name this program as part4.c
 Expand the functionality of the simulator in part 3 to allow the simulator to execute
instruction “LDI”.
 For this part, the simulator should display the hexadecimal code of each LDI instruction
that has been executed and the state of the LC‐3 machine after each LDI instruction is executed. The hexadecimal code of each LDI instruction should be preceded with “after executing instruction\t” (where \t denotes a tab character) and “0x”.
 The simulator should output a line consisting of 18 “=” after displaying the state of the LC‐3 machine.
Here is an example of the execution of the program. In this example, the LC‐3 assembly program is as below. The name of the executable of the assembly program is “p4.obj” (NOTE: “p4.obj” is the exact name of the file. That is, the file name does NOT have a ‘.txt’ suffix.). Markers will probably use a file with a different name and different contents).

.ORIG X4500

LD R0, A LEA R1, B LDI R2, C

F HALT

A .FILL
B .FILL
C .FILL
.END

The execution of the program is shown below. The command line arguments are marked in red.

X560A
X4507
X4501

    $ ./part4 p4.obj
    after executing instruction

R0 0x560a
R1 0x4505
R2 0xe203
R3 0x0000
R4 0x0000
R5 0x0000
R6 0x0000
R7 0x0000

    PC      0x4503
    IR      0xa403
    CC      N
    ==================

Part 5 (3 marks)

0xa403

This part is based on Part 4.

 Name this program as part5.c
 Expand the functionality of the simulator in part 4 to allow the simulator to execute

instruction “AND”.

 For this part, the simulator should display the hexadecimal code of each AND instruction that has been executed and the state of the LC‐3 machine after each AND instruction is executed. The hexadecimal code of each AND instruction should be preceded with “after executing instruction\t” (where \t denotes a tab character) and “0x”.
 The simulator should output a line consisting of 18 “=” after displaying the state of the LC‐3 machine.
Here is an example of the execution of the program. In this example, the LC‐3 assembly program is as below. The name of the executable of the assembly program is “p5.obj” (NOTE: “p5.obj” is the exact name of the file. That is, the file name does NOT have a ‘.txt’ suffix.). Markers will probably use a file with a different name and different contents).

.ORIG X4500

LD R0, A
LEA R1, B
LDI R2, C
AND R3, R0, R1 AND R3, R1, #0

F HALT

A .FILL
B .FILL
C .FILL
.END

The execution of the program is shown below. The command line arguments are marked in red.

X560A
X4507
X4501

    $ ./part5 p5.obj
    after executing instruction

R0 0x560a
R1 0x4507
R2 0xe205
R3 0x4402
R4 0x0000
R5 0x0000
R6 0x0000
R7 0x0000

    PC      0x4504
    IR      0x5601
    CC      P
    ==================
    after executing instruction

R0 0x560a
R1 0x4507
R2 0xe205
R3 0x0000
R4 0x0000
R5 0x0000
R6 0x0000
R7 0x0000

    PC      0x4505
    IR      0x5660
    CC      Z
    ==================

Part 6 (3 marks)

0x5601

0x5660

This part is based on Part 5.

 Name this program as part6.c
 Expand the functionality of the simulator in part 5 to allow the simulator to execute
instruction “NOT”.
 For this part, the simulator should display the hexadecimal code of each NOT instruction
that has been executed and the state of the LC‐3 machine after each NOT instruction is executed. The hexadecimal code of each NOT instruction should be preceded with “after executing instruction\t” (where \t denotes a tab character) and “0x”.
 The simulator should output a line consisting of 18 “=” after displaying the state of the LC‐3 machine.
Here is an example of the execution of the program. In this example, the LC‐3 assembly program is as below. The name of the executable of the assembly program is “p6.obj” (NOTE: “p6.obj” is the exact name of the file. That is, the file name does NOT have a ‘.txt’ suffix.). Markers will probably use a file with a different name and different contents).

.ORIG X4500

LD R0, A
LEA R1, B
LDI R2, C
AND R3, R0, R1 AND R3, R1, #0 NOT R4, R3

F HALT

A .FILL
B .FILL
C .FILL
.END

The execution of the program is shown below. The command line arguments are marked in red.

X560A
X4507
X4501

    $ ./part6 p6.obj
    after executing instruction

R0 0x560a
R1 0x4508
R2 0xe206
R3 0x0000
R4 0xffff
R5 0x0000
R6 0x0000
R7 0x0000

    PC      0x4506
    IR      0x98ff
    CC      N
    ==================

Part 7 (3 marks)

This part is based on Part 6.
 Name this program as part7.c

0x98ff

 Expand the functionality of the simulator in part 7 to allow the simulator to execute instruction “ADD”.
 For this part, the simulator should display the hexadecimal code of each ADD instruction that has been executed and the state of the LC‐3 machine after each ADD instruction is executed. The hexadecimal code of each ADD instruction should be preceded with “after executing instruction\t” (where \t denotes a tab character) and “0x”.
 The simulator should output a line consisting of 18 “=” after displaying the state of the LC‐3 machine.
Here is an example of the execution of the program. In this example, the LC‐3 assembly program is as below. The name of the executable of the assembly program is “p7.obj” (NOTE: “p7.obj” is the exact name of the file. That is, the file name does NOT have a ‘.txt’ suffix.). Markers will probably use a file with a different name and different contents).

.ORIG X4500

LD R0, A
LEA R1, B
LDI R2, C
AND R3, R0, R1 AND R3, R1, #0 NOT R4, R3 ADD R4, R4, #1

F HALT

A .FILL
B .FILL
C .FILL
.END

The execution of the program is shown below. The command line arguments are marked in red.

X560A
X4507
X4501

    $ ./part7 p7.obj
    after executing instruction

R0 0x560a
R1 0x4509
R2 0xe207
R3 0x0000
R4 0x0000
R5 0x0000
R6 0x0000
R7 0x0000

    PC      0x4507
    IR      0x1921
    CC      Z
    ==================

Part 8 (3 marks)

0x1921

This part is based on Part 7.

 Name this program as part8.c
 Expand the functionality of the simulator in part 7 to allow the simulator to execute

instruction “BR”.

 For this part, the simulator should display the hexadecimal code of each BR instruction that has been executed and the state of the LC‐3 machine after each BR instruction is executed. The hexadecimal code of each BR instruction should be preceded with “after executing instruction\t” (where \t denotes a tab character) and “0x”.
 The simulator should output a line consisting of 18 “=” after displaying the state of the LC‐3 machine.
Here is an example of the execution of the program. In this example, the LC‐3 assembly program is as below. The name of the executable of the assembly program is “p8a.obj” (NOTE: “p8a.obj” is the exact name of the file. That is, the file name does NOT have a ‘.txt’ suffix.). Markers will probably use a file with a different name and different contents).

.ORIG X4500

LD R0, A
LEA R1, B
LDI R2, C
AND R3, R0, R1 AND R3, R1, #0 NOT R4, R3 ADD R4, R4, #1 BRp F
ADD R3, R3, #1

F HALT

A .FILL
B .FILL
C .FILL
.END

The execution of the program is shown below. The command line arguments are marked in red.

X560A
X4507
X4501

$ ./part8 p8a.obj
after executing instruction

R0 0x560a
R1 0x450b
R2 0xe209
R3 0x0000
R4 0x0000
R5 0x0000
R6 0x0000
R7 0x0000

PC      0x4508
IR      0x0201
CC      Z
==================

0x0201

Here is another example of the execution of the program. In this example, the LC‐3 assembly program is as below. The name of the executable of the assembly program is “p8b.obj” (NOTE: “p8b.obj” is the exact name of the file. That is, the file name does NOT have a ‘.txt’ suffix.). Markers will probably use a file with a different name and different contents).

.ORIG X4500 LD R0, A LEA R1, B

LDI R2, C
AND R3, R0, R1 AND R3, R1, #0 NOT R4, R3 ADD R4, R4, #1 BRzp F
ADD R3, R3, #1

F HALT

A .FILL
B .FILL
C .FILL
.END

The execution of the program is shown below. The command line arguments are marked in red.

X560A
X4507
X4501

    $ ./part8 p8b.obj
    after executing instruction

R0 0x560a
R1 0x450b
R2 0xe209
R3 0x0000
R4 0x0000
R5 0x0000
R6 0x0000
R7 0x0000

    PC      0x4509
    IR      0x0601
    CC      Z
    ==================

Part 9 (1 mark)

0x0601

1 mark for having no compile warning messages for all the submitted programs.

Submission

You MUST thoroughly test your program on login.cs.auckland.ac.nz before submission.
Programs that cannot be compiled or run on login.cs.auckland.ac.nz will NOT get any

mark.
Use command “tar cvzf A3.tar.gz part1.c part2.c part3.c part4.c part5.c part6.c part7.c
part8.c” to pack the eight C programs to file A3.tar.gz. [Note: You MUST use the tar command on login.cs.auckland.ac.nz to pack the files as files packed using tools on PC cannot be unpacked on login.cs.auckland.ac.nz. You will NOT get any mark if your file cannot be unpacked on login.cs.auckland.ac.nz.]
Submit A3.tar.gz through Canvas. The markers will only mark your latest submission.
NO email submission will be accepted.

Resource

 The binary files used in the examples of the specifications are packed in file A3Examples.tar.gz.
 The scripts used by the markers to check your programs’ outputs are also packed in A3Examples.tar.gz. To ensure that the outputs of your programs conform to the required output format, I STRONGLY suggest you use the scripts to check the outputs of your programs when you use the examples in the specification to test your programs. If the outputs and the format of the outputs are correct, you should see a “part X passes the test” message. WHEN YOUR PROGRAMS ARE MARKED, OUTPUTS THAT DO NOT CONFORM TO THE REQUIRED FORMAT WILL FAIL THE TEST AND WILL GET 0 FOR THE FAILED CASES.
 Follow the steps below to extract and to use the files in A3Examples.tar.gz

o Put A3Examples.tar.gz in the directory in which your programs are stored.
o Use command “tar xvf A3Examples.tar.gz” to unpack A3Examples.tar.gz. After

unpacking the file, the “.obj” files and the marking scripts should be extracted to the

same directory as your programs.
o Once you are satisfied with the outputs of your program, you can run the marking

scripts to check the outputs and the formats of the outputs of your programs using the marking scripts. There is one marking script for each part. The marking script for part 1 is “m1.bash”; the script for part 2 is “m2.bash”; and so on.

o To run a script, use command “./mX.bash” where X is a digit. For example, to run the marking script for part 1, use command “./m1.bash”.

o The marking scripts only check the outputs of the programs for the examples given in the specification.

 You should create more test cases to manually test your programs. The easiest way is to use LC‐3 assembler to generate the binary “.obj” file and upload the file to login.cs.auckland.ac.nz for testing. You can use the official LC‐3 simulator to check whether the outputs of your programs are correct.

Debugging Tips

Debugging is a skill that you are expected to acquire. Once you start working, you are paid to write and debug programs. Nobody is going to help you with debugging. So, you should acquire the skill now. You can only acquire it by practicing.
If you get a “segmentation faults” while running a program, the best way to locate the statement that causes the bug is to insert “printf” into your program.
If you can see the output of the “printf” statement, it means the bug is caused by a statement that appears somewhere after the “printf” statement. In this case, you should move the “printf” statement forward. Repeat this process until you cannot see the output of the “printf” statement.
If you cannot see the output of the “printf” statement, it means the bug is caused by a statement that appears somewhere before the “printf” statement.
Combining step 3 and 4, you should be able to identify the statement that causes the “segmentation faults”.
Once you identify the statement that causes the “segmentation faults”, you can analyse the cause of bug, e.g. whether the variables have the expected values.

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