Computing Machinery I

Assignment 3

Objective

The objective of this assignment is to practice binary multiplication, division, and shifting in ARMv8

assembly.

Skills Needed for this Assignment:

• Ability to work with basic arithmetic, loops, and if-else constructs in assembly

• Ability to print to standard output using the printf() and scanf() functions

• Ability to use shifting instructions to implement multiplication

• Ability to assemble programs using gcc and use m4 to process macros

• Ability to use gdb to debug and display assembly language programs

Overview

Your programs will convert decimal numbers to binary and vice-versa.

Details

1. The first program converts a binary number to decimal. It prompts the user for N,a number entered in

binary. For reading N, you will need to call the C library scanf() function. Read it as a long integer.

Let M be any number; we will refer to the least significant bit in M as M[0]. Implement the following

algorithms to convert N to a decimal value:

Binary to decimal:

If N is negative, pos_N = 2s complement of N

Else, pos_N = N

decimal_N = 0

For (i = 0; i < 64; i++) {

If pos_N(0) is 1 {

Decimal_N = decimal_N + 2i

}

pos_N >> 1

}

If N is negative, decimal_N = –decimal_N

Calculating 2i

:

Pow_2 = 1

For (i = 0; i < n; i++) {

Pow_2 << 1

}

2. The second program converts a decimal number or binary. The user enters a decimal value N. Use the

following algorithm:

Decimal to binary:

If N is negative, decimal_N = –decimal_N

binary_N = 0

quotient = N

i = 0

while quotient != 0 {

quotient, remainder = quotient / 2

// Divide quotient by 2 producing a new quotient and a remainder

remainder = remainder << i

binary_N = binary_N | remainder

i++

}

If N is negative, binary_N = 2s complement of binary_N

You do not need to check for a valid input (especially for program 1 where the entered number must be

binary). Make sure your code is properly formatted into columns, is readable and fully documented, and

includes identifying information at the top of each file. You must comment each line of assembly code.

Your code should also be well designed: make sure it is well organized, clear, and concise.

Submission

• Note: The TA may provide further submission instructions

• Name your programs assign3a.asm (binary to decimal) and assign3b.asm (decimal to binary)

• Create a script file for each program. Call them assign3a.script and assign3b.script. Both script

files must contain a GDB session.

• Submit a README file providing extra instructions or information for your TA (optional)

• Submit your work to the appropriate dropbox on D2L.

Late Submission Policy

Late submissions will be penalized as follows:

-12.5% for each late day or portion of a day for the first two days

-25% for each additional day or portion of a day after the first two days

Hence, no submissions will be accepted after 5 days (including weekend days) of the announced deadline.

Academic Misconduct

This assignment is to be done by individual students: your final submission must be your own original

work. Teamwork is not allowed. Any similarities between submissions will be further investigated for

academic misconduct. While you are encouraged to discuss the assignment with your colleagues, this must

be limited to conceptual and design decisions. Code sharing by any means is prohibited, including looking

at someone else’s paper or screen. The submission of compiler generated assembly code is absolutely

prohibited. Any re-used code of excess of 5 lines in C and 10 lines in assembly (10 assembly language

instructions) must be cited and have its source acknowledged. Failure to credit the source will also result in

a misconduct investigation.

D2L Marks

Marks posted on D2L are subject to change (up or down).

Computing Machinery I

Assignment 3 Rubric

Student:__________________________________________

Item Max Points Points

Code compiles 5

Code runs 5

Calculating 2i 5

Binary to decimal 30

Decimal to binary 30

Handling negative numbers (both programs) 10

Code readability (formatting and documentation) 15

Total Points 100