Instruction Execution

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.

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.
•  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 instructiont” (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.

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 instructiont” (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.

Part 4 (3 marks)
This part is based on Part 3.

•  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 instructiont” (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.

Part 5 (3 marks)
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 instructiont” (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.

Part 6 (3 marks)
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 instructiont” (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.

Part 7 (3 marks)
This part is based on Part 6.

•  Name this program as part7.c
•  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 instructiont” (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.Part 8 (3 marks)

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 instructiont” (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.Part 9 (1 mark)

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