Operating Systems $($CS $330)$

Assignment $01$

High$-$Level, Assembly and Machine Languages

Submission Date: Wednesday, $7$th February $2024$

Important instructions

$1)$ Complete explanation must be handwritten, no typed assignments will be

accepted

$2)$ Please upload the $$pdf$$ on the LMS

$3)$ Screenshots must be included in the assignment.

$4)$ If the assignment is not on the LMS it will not be graded

In this assignment you will explore assembly and machine languages. You already know

that when a high$-$level language program is compiled a machine language program gets

generated that can be directly executed. What does such a machine language program

look like? How can an $.$exe file be viewed and modified?

$($a$)$ As a first step you will first write a simple C program to add two integers and

compile it with gcc $($GNU C compiler$).$ As an example, the following is the

$$Hello World$$ program in C$.$ You can modify it to make it add two integers.

#include

#include

int main$($int argc, char $**$argv$)\{$

printf$("$Hello World of C$")$;

$\}$

The compilation command in Linux would be: gcc $$o HelloWorld

HelloWorld.c assuming that this program is saved in the file

HelloWorld.c $.$ Completing $($a$)4/10$

$($b$)$ The compiler gcc has an option to generate the compiled code is assembly

language. Find out how such an option can be used and use it to generate

assembly language code for your high$-$level program for adding two integers.

View this file and note the point where the two numbers get added in assembly.

You may also use the Linux utility: objdump $$d exe file name, to disassemble

the exe file into assembly and see the instruction for adding the two numbers.

Completing $($b$)$ if the student was able to do $($b$)$ and locate the instructions

for adding the two numbers $7/10$

$($c$)$ Next, edit the executable file generated by gcc in step $($a$),$ to change the addition

operation to a subtraction operation. You will have to do some research here to

find out the op code for subtraction instruction and other issues. $($Use editors

available freely online for editing executable files and other binary files for this

purpose. One such editor is hexedit, but it would be best that you search online

for a better option.$)$ After modifying the code try to run the executable to see if

Page $2$ of $2$

you have succeeded. If not try to explain why you failed. Completing $($b$)$ if the

student was able to do $($c$)10/10$

$($d$)$ Java compiler, javac, compiles Java language files to java byte code $($not the

machine language instructions$)$ which is executed by the Java Virtual Machine

$($JVM$).$ Try to find out how a Java byte code file can be viewed. Can source files

be generated for Java byte code?