CS2208b Assignment 4

CS2208b Assignment 4

For this assignment, only an electronic submission (attachments) at owl.uwo.ca is required.
 Attachments must include:
o ONE pdf file (named report2.pdf) that has the one flowchart, program documentations, and any
related communications, if any.
o ONE Text files (named question1.s) that has softcopy of the assembly source program you wrote.
 So, in total, you will submit 1 + 1 = 2 files (report2.pdf and question1.s)
 Failure to follow the above format may cost you 10% of the total assignment mark.
Late assignments are strongly discouraged
 10% will be deducted from a late assignment (up to 24 hours after the due date/time)
 After 24 hours from the due date/time, late assignments will receive a zero grade.
In this assignment, you will use the micro Vision ARM simulator by Keil, which is an MS Windows based
software, to develop the required programs in this assignment. The simulator (version 4) has been installed on all
PCs at GEN labs, except NCB-105.
The Keil micro Vision simulator may also be installed on your Windows PC. You just need to download it from
OWL and install it.
Programming Style
Programming style is very important in assembly language. It is expected to do the following in your programs:
 Using EQU directive to give a symbolic name to a numeric constant to make it more readable.
 Applying neat spacing and code organization:
o Assembly language source code should be arranged in three columns: label, instruction, and comments:
 the label field starts at the beginning of the line,
 the instruction field (opcodes + operands) starts at the next TAB stop, and
 the comments are aligned in a column on the right.
 Using appropriate label names.
 Commenting each assembly line
 Commenting each logical part of your code.
Great Ways to Lose Marks
 Not grouping your lines into logical ideas
 Not appropriately using whitespace
 Not bothering to comment your code
 Commenting the code by just stating what you're doing, instead of why, e.g.,
MOV r0, #5 ;move 5 into r0
 Not paying attention to the programming style (see the previous paragraph)
 Not optimizing your code by using unnecessary assembly instructions. The more instructions in your program
the less your mark will be.
 Handing in your code as soon as it assembles, without testing and validating your code
 Not using proper flowchart symbols
 Not following the flowchart rules 
Copyright © 2019 Mahmoud El-Sakka.
QUESTION 1 (100 marks)
A string is an array representing a sequence of characters. To store a string of n characters in your program, you need to set
aside n+1 bytes of memory. This allocated memory will contain the characters in the string, plus one extra special
character—the null character—to mark the end of the string. The null character is a byte whose bits are all zeros (0x00). The
actual string consists of any group of characters, which none of them can be the null character.
Draw a detailed flowchart and write an ARM assembly language program to copy a null terminated STRING1 to a null
terminated STRING2, after removing any occurrences of the word “the” (case sensitive) in STRING1. I.e., if STRING1 is
“the woman and The man said the” then STRING2 would become “ woman and The man said ”.
However, if STRING1 is “and they took breathe” then STRING2 would become
“and they took breathe” without any change. You can assume that STRING2 will be less than 255 characters.
Your code should be highly optimized. Use as few instructions as possible (as little as 30 assembly instructions only,
NOT including any assembly directives or data definitions)!!.
Define the data of this program in a separate DATA area.
Define the strings as follow:
STRING1 DCB "and the man said they must go" ;String1
EoS DCB 0x00 ;end of string1
STRING2 space 0xFF ;just allocating 255 bytes
More test cases:
"the the the 123 the"  " 123 "
""  ""
"the"  ""
"The"  "The"
"them the the1"  "them the1"