Description
Problem 1 [B] [1 marks, submit to PS1P01]
Write a VAL program that tests whether the sum of all the registers eax, ebx, ecx, edx,
esi, and edi, is odd or even. At the end of the program, register eax should contain the
result: 0 if the sum is even, and 1 if the sum is odd.
Problem 2 [C] [2 marks, submit to PS1P02]
Write a VAL program that converts a string made up of digit characters (‘0’..’9’) into the 4-
byte unsigned numeric value corresponding to that string. Your program should assume that
the string resides in memory at the address pointed to by register esi, and should return the
result in register eax.
Problem 3 [A] [4 marks, submit to PS1P03]
Write an interpreter for the following language, which we shall call L. Programs of the
language L are sequences of simple instructions (no whitespaces are allowed). Each
instruction has the form
????????⊗=???????;
where variable is a variable name, following the syntax of C identifiers, ⊗ is any of the
operators +, -, *, or /, and operand is either a variable, or an unsigned integer. The
instruction is terminated by semicolon. All the variables are considered to be initialized with
0 before the program starts execution. The interpreter should print the values of all the
Submission: In IVLE, in the cs2104 workbin, you will find a folder called “Homework
submissions”. In that folder, there are currently 5 subfolders: PS1P01,…,PS1P05. The
last two digits of the folder name indicate the solution that is to be submitted into that folder: the
solution to Question 1 into PS1P01, and so on (that is, you need to submit 5 separate solutions to
5 questions). A solution should consist of a single text file that can be compiled, or loaded into the
interpreter of interest and executed. You should provide as much supplementary information about
your solution as you can, in the form of program comments.
12 marks
variables in the program at the end of the execution. Your interpreter should be implemented
in C.
Execution example:
For the input string: “x+=3;y+=5;x*=y;”
Interpreter output: x = 15 y = 5
Hint: Implement your interpreter as a deterministic finite automaton (slide 15 in cs2104-
L02-pre.pdf).
Problem 4 [C] [2 marks, submit to PS1P04]
Write an VAL program that computes the first N prime integers (each taking up a space of 4
bytes), where N is a parameter of the program that is made available in register ecx. The
prime numbers you compute should be placed in increasing order in the memory area with
the address range 0 … 4*N.
Problem 5 [A] [3 marks, submit to PS1P05]
In VAL, a linked list is implemented in the following way. Each list element is an 8-byte
entity, whereby the first group of 4 bytes represents the data field of the element, and the
second group of 4 bytes represents the pointer to the next element. In our case, the 4 data
field bytes shall be interpreted as an integer. Thus, list elements are sequenced together by
interpreting the second group of 4 bytes in an element as the address of the next element in
the list. The last element in the list has this “next element” field set to 0 (implying that no list
element can reside at address 0).
Write a VAL program that receives the address of a list in register esi, and computes the
sum of the elements in the list. To test your program, write a main function that sets up a
linked list with the elements placed in memory in as much a random fashion as possible (but
remember not to place a list element at address 0). Your main function should then call
exec(), and then finally print the value of eax, which should be the desired result of the
VAL program.