代写INF2C留学生、代做C/C++语言、MIPS Assembly Language Programming代写

日期：2018-10-17 10:15

INF2C Computer Systems

Coursework 1

MIPS Assembly Language Programming

Deadline: Wed, 24 Oct (Week 6), 16:00

Instructor: Boris Grot

TA: Siavash Katebzadeh

The aim of this assignment is to introduce you to writing simple programs in MIPS

assembly and C languages. The assignment asks you to write three MIPS programs

and test them using the MARS IDE. For details on MARS, see Lab Exercise 1. The

assignment also asks you to write C code and use C code versions of the programs as

models for the MIPS versions.

This is the first of two assignments for the INF2C Computer Systems course. It is

worth 50% of the coursework mark for INF2C-CS and 20% of the overall course mark.

Please bear in mind the guidelines on academic misconduct from Undergraduate year

2 student handbook available at http://web.inf.ed.ac.uk/infweb/student-services/

ito/students/year2.

1 Preliminaries

One of the most common and simplest tools that can assist the user with writing is

a spell checker. A spell checker is a program or function of a program which determines

the correctness of the spelling of a given word based on the language set being used.

The main focus of this exercise is to implement a spell checker for a subset of the

English language in C and MIPS.

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1.1 Task A: Tokenizer

The first task is a warm-up exercise. It helps you get familiar with the basic structure

of MIPS and C programs, and with using the MARS IDE.

In this task, an input file is used. The input file is a text document, consisting of

alphabetic characters (a-z and A-Z), punctuation marks ,.!? (i.e., comma, period,

exclamation, question mark) and spaces in any order and combination (without any

newlines). The input file is terminated by End-of-File (EOF). A valid input file does

not include any other characters.

You are given a MIPS file named tokenizer.s which contains a skeleton of your

program. This skeleton reads an input file named input.txt and stores its content into

a null-terminated string named content. Your task is to break the content string into

a list of tokens and output them, one token per line.

A token consists of one or more consecutive characters of exactly one of the following

three different character types:

1. Alphabetic characters, which includes only alphabetic characters (a-z and A-Z)

e.g. ’CompSys’

2. Punctuation marks, which includes only punctuation mark characters

3. Spaces, which includes only space characters (’ ’)

e.g. ’ ’

If the content of the input file is:

Let go your earthly tether. Enter the void... Empty,and become wind.

then the output of your program should look like:

Let

go

your

earthly

tether

.

Enter

the

2

void

...

Empty

,

and

become

wind

.

A good way to go about writing a MIPS program is to first write an equivalent C

program. It is much easier and quicker to get all the control flow and data manipulations

correct in C than in MIPS. Once the C code for a program is correct, one can translate

it to an equivalent MIPS program statement-by-statement. To this end, a C version of

the desired MIPS program is provided in the file tokenizer.c.

For convenience, the C program includes definitions of functions such as read string

and print char, which mimic the behaviour of MARS system calls with the same names.

Derive your MIPS program from this tokenizer.c C program.

Do not try optimizing your MIPS code. Aim to keep the correspondence with the C

code as clear as possible. Use your C code as comments in the MIPS code to explain

the structure. Then put additional comments to document the details of the MIPS

implementation.

As a model for creating and commenting your MIPS code, have a look at the supplied

file hex.s and the corresponding C program hex.c. These are versions of the hexOut.s

program from the MIPS lab which converts an entered decimal number into hexadecimal.

1.2 Task B: Spell Checker

The goal of this task is to write a program that detects misspelled words in a string

and marks them in the output. A word is not misspelled if it exists in the dictionary.

All characters in the dictionary are lowercase. For the purposes of this exercise, spell

checking will be case insensitive. Thus, ’tHen’ is a correct spelling of a dictionary word

’then’.

This task requires an input file similar to the one in Task A. In addition to this

input file, we also use a dictionary file. The dictionary file consists of English words in

lowercase alphabetic characters (a-z) delimited by a newline (\n) and terminated by

End-of-File (EOF). A valid dictionary does not include any other characters.

You are given a MIPS file named spell checker.s that contains a skeleton of your

program. This skeleton reads an input file named input.txt and stores its content

into a null-terminated string named content. It also reads a dictionary file named

dictionary.txt and stores its content into a null-terminated string named dictionary.

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In this task, you will write a program in both C and MIPS, that in the first step,

tokenizes the content string and in the second step, checks whether each Alphabetic

token is correct; if not, the program marks it by putting underscores ( ) at the beginning

and end of the token. In the final step, the program outputs all of tokens.

If the content of a given input file is:

Everybody is speciall.Everybody.. Everybody is a HeRo, a luver, a fool,

a villain!! Everybody... Everybody has thier story to tell.

then the output of your program should look like:

Everybody is _speciall_.Everybody.. Everybody is a HeRo, a _luver_, a

fool, a villain!! Everybody... Everybody has _thier_ story to tell.

Approach this task by first writing an equivalent C program spell checker.c and

then translating this C program into a MIPS program spell checker.s. Before translating,

you should compile and test your C program. Ensure it is working correctly

before starting on the MIPS code. To help you get started with the C program, an

outline spell checker.c is supplied. Furthermore, you can reuse the Tokenizer of Task

A to extract the tokens from the content string. We recommend structuring the code

into functions for ease of development and readability. See section 2.2 for further advice

and requirements on MIPS code.

As in Task A, use the C code to comment your MIPS code, and put additional

comments for MIPS-specific details. In your C program, your comments should focus

on explaining the higher-level features of your program, so your comments in the MIPS

code can mainly just concern themselves with the MIPS implementation details.

1.3 Task C: Punctuation Checker

The goal of this task is to extend Task B by adding basic punctuation checking

to your program. In this task, in addition to spell checking (Task B), your program

(punctuation checker.s) also has to detect punctuation errors and inconsistencies in

the content string and mark them in the output. The rules of correctness of Punctuation

tokens are shown in Table 1. The rules are sorted according to their priority, with higher

priority rules on top. These rules must be evaluated and executed sequentially against

each token.

If the content of a given input file is:

Everybody is speciall.. Everybody. Everybody is a HeRo ,a luver, a fool,a

villain!! Everybody... Everybody has thier story to tell....

then the output of your program should look like:

Everybody is _speciall__.._ Everybody. Everybody is a HeRo _,_a _luver_,

a fool_,_a villain_!!_ Everybody... Everybody has _thier_ story

to tell_...._

While you are encouraged to write a C program to facilitate the MIPS implementation,

you should not submit the C program for this task.

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Punctuation Token Correct Incorrect Example

has a Space token before it Hello .Is

has an Alphabetic token after it Hello.Is

has ellipsis (”...”) now...

has only one punctuation mark yours?

has more than one punctuation marks Really?!

other

Table 1: Grammar checker rules

1.4 Assumptions and Restrictions on Program Inputs

Your programs in both tasks will be tested against dictionary and input files that

adhere to the following rules:

A dictionary file will contain a maximum of 10,000 words.

A single word in the dictionary file will contain a maximum of 20 lowercase alphabetic

characters.

An input file will be a maximum of 2048 characters including spaces and without

any newline character.

An input file may contain alphabetic (a-z, A-Z), punctuation marks (,.!?) and

space (’ ’) characters.

1.5 Restrictions on the use of C Library Functions

The only C library functions that can be used are fgets and printf, which are called

within the functions print char, print int, print string and read string provided

with the C files.

1.6 Output

For your convenience, the output function is provided in both C files. You can use

it to output a string. Make sure your program does not print anything other than what

is printed by the output function as it may interfere with automated marking. In MIPS

programs, you should output exactly the same way as done in C programs.

2 Program Development and Testing

2.1 C

You can compile a C program written in a file called, for instance, prog.c at the

command prompt on the DICE machines with the following command:

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gcc -o prog prog.c

If compilation succeeded without any errors, it creates an executable prog which can

then run by entering:

./prog

2.2 MIPS

You will need to choose what kind of storage to use in MIPS for all variables from

the C code. In all tasks, we recommend you to store all tokens in the data segment. Use

the .space directive to reserve space in the data segment for arrays, preceding it with

an appropriate .align directive if the start of the space needs to be aligned to a word

or other boundary.

In the MIPS implementation of Tasks B and C, you must call at least one function

written by you. Function calls are optional in the implementation of Task A, and you are

allowed to use the same function(s) in all three tasks, if you wish. You are also allowed

to have multiple functions and nested function calls. Which functionality to abstract

into a separate function(s) is entirely up to you. To reiterate, the only requirement is

having at least one call to a user-defined function in Tasks B and C.

You must abide by the MIPS register convention. Remember that values of $t* registers

are not guaranteed to be preserved across function call invocations (including both

syscall and user-defined functions), whereas values of $s* registers will be preserved.

However, do not use only $s* registers in your code; make use of $t* registers when

appropriate.

Ultimately, you must ensure that your MIPS programs assemble and run without

errors when using MARS. When testing your programs, we will run MARS from the

command line. Please check that your MIPS programs run properly in this way before

submitting them. For example, if the MARS JAR file is saved as mars.jar in the same

directory as a MIPS program prog.s, running the following command at the commandline,

assembles and then runs prog.s.

java -jar mars.jar sm prog.s

Notes:

1) The sm option tells MARS to start running at the main label rather than with

the first instruction in the code in prog.s. When running MARS with its IDE, marking

the check-box for Initialize Program Counter to global ’main’ if defined on the Settings

menu achieves the same effect.

2) MARS supports a variety of pseudo-instructions, more than the ones that are described

in the MIPS appendix of the Hennessy and Patterson book. In the past, we have

often found errors and misunderstandings in student code relating to the inadvertent use

of pseudo-instructions that are not documented in this appendix. For this reason, make

sure you only use pseudo-instructions that are explicitly mentioned in the appendix.

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3 Submission

Submit your work using the command

submit inf2c-cs cw1 tokenizer.s spell checker.c spell checker.s punctuation checker.s

at a command-line prompt on a DICE machine. Unless there are special circumstances,

late submissions are not allowed. Please consult the online undergraduate year 2

student handbook for further information on this.

You can submit more than once up until the submission deadline. All submissions

are timestamped automatically. Identically named files will overwrite earlier submitted

versions, so we will mark the latest submission that comes in before the deadline.

Warning: Unfortunately the submit command will technically allow you to submit

late even if you submitted before the deadline. Don’t do this! We can only retrieve the

latest version, which means you will be penalized for submitting late.

For additional information about late penalties and extension requests, see the School

web page below. Do not email any course staff directly about extension requests; you

must follow the instructions on the web page. http://web.inf.ed.ac.uk/infweb/

student-services/ito/admin/coursework-projects/late-coursework-extension-requests

4 Assessment

Your programs will be primarily judged according to correctness, completeness, and

correct use of MIPS instructions, registers and function call convention.

In both C and MIPS programming, commenting a program and keeping it tidy is

very important. Make sure that you comment the code throughout and format it neatly.

A proportion of the marks will be allocated to these aspects of your code.

When editing your code, please make sure you do not use tab characters for indentation.

Different editors and printing routines treat tab characters differently, and, if you

use tabs, it is likely that your code will not look pretty when we come to mark it. If you

use emacs, the command (m-x)untabify will remove all tab characters from the file in

a buffer.

5 Similarity Checking and Academic Misconduct

You must submit your own work. Any code that is not written by you must be

clearly identified and explained through comments at the top of your files. Failure to

do so is plagiarism. Detailed guidelines on what constitutes plagiarism can be found at

http://web.inf.ed.ac.uk/infweb/admin/policies/guidelines-plagiarism.

All submitted code is checked for similarity with other submissions using the MOSS

system 1

. MOSS has been effective in the past at finding similarities. It is not fooled by

name changes and reordering of code blocks.

1http://theory.stanford.edu/~aiken/moss/

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6 Questions

If you have any questions about the assignment, please start by checking existing

discussions on Piazza. If you can’t find the answer to your question, start a new discussion

– chances are, others have already encountered (and, possibly, solved) the same

problem. The TA and the course instructor will also monitor Piazza and contribute to

the discussions. You should also take advantage of the labs and the lab demonstrators

who are there to answer your questions.