代做EEE125、代写C/C++编程、代做program writing、代做C/C++语言

日期：2018-12-12 09:33

EEE125 Programming in ‘C’ Course: program writing assignment

At the first lecture I discussed the make-up of this course and explained that the course would be assessed by

means of a MOLE exam (worth 30% of the available marks) that has already taken place, this C assignment task

(also worth 30%), then in semester 2 some Matlab in-class assessments (worth 10%) and a final in-class C

program writing exam (worth 30%).

For this assessed assignment you are asked to write a program in ‘C’ to carry out the particular task

detailed here.

1 Administrative details

Your program must be handed in via MOLE. The hand-in date for this exercise is 11.59pm on Tuesday 11th

December. You can hand your work in there anytime between now and that date.

Late submission will result in a deduction of 5% of the total mark awarded for each working day after the

submission date, this is Faculty policy. (Working days – Monday to Friday - include working days within

standard vacation times). The only exceptions to this will usually be where illness or other serious

extenuating circumstances have meant missing the hand-in date (medical evidence will often be needed to

sustain this exception). In such circumstances you MUST submit an Extenuating Circumstances form (not

a self-certification form), available from www.sheffield.ac.uk/ssid/forms/circs, (before completing such a

form make sure you read the explanatory notes here first: http://www.sheffield.ac.uk/ssid/forms/circsnotes)

hand the form in to the department Student Support Office (Suite 27, level 1, 3 Solly Street building) or

email directly to me.

If you believe you have good reason to ask for an extension to this hand-in date, you may discuss the

circumstances with Peter Judd and, at his discretion, a later hand-in date may be negotiated. (But please do the

discussing well in advance of the original hand-in date expiring). Please note: being disorganised or lazy and

so failing to meet the hand-in date by simply leaving tackling the exercise until it's too late is not a “good

reason” and will not normally result in an extension of the hand-in date!

________________________________________________________________________________________

2 What your program should do

Elsewhere in your studies you may have heard of the “Least Squares” method often used to generate a “best fit” straight

line through a set of data plotted on a graph (where a straight line relationship is expected to exist). The "Least Squares"

method is very useful when working with data derived from experiments and indeed it may well be a technique of use to

you elsewhere in course work.

The aim of this assessed exercise is: for you to write a program in 'C' that uses the least squares technique to allow a user

to input a set of data value and to compute and output as results the gradient (m) and offset (c) of the “best fit” straight line

through that entered set of data. You do not have need understand the underlying mathematics (though it would help) instead

all you need to do is correctly implement the formulae given in this assignment sheet.

2.1 The "Least Squares" formulae needed

Consider you have a set of data comprising pairs of measurements of two related variables: ‘x’ & ‘y’. You believe

the relationship between these variables can be expressed as a straight line, using the standard straight line

equation (where y is the dependent variable and x is the independent variable, m is the gradient of the line - that

is the rate of change of y with respect to x - and c is the intercept (or ‘offset’) of the line with the y axis – that is

the value of y when x is zero). Here is the standard straight line equation:

y = m. x + c

U:\C\c-18-19\Tutorial\Assessed_Exercise_No_1\Assess-1-2018-19.docx - 2 - (? Peter Judd/University of Sheffield '98-'18)

Look at the example graph shown below. Pairs of x, y data have been plotted (the little ‘+’ marks) and a best fit

straight line drawn through them (the dotted line). The gradient of the “best fit” straight line is ‘m’ and the

intercept (offset) of that line with the y axis from the origin of the graph is ‘c’.

From theory we can obtain the equations needed to

draw a best fit straight line through such a set of data

using “Least Squares” as our technique.

Consider we have a set of data samples where values of

‘y’ have been measured for a range of different values

of ‘x’. Consider we have taken ‘N’ samples (i.e. pairs

of x and y data of the form: [x1 y1] [x2 y2] [x3 y3] … [xN

yN]). Then using this notation we can write the

following equations:

The least squares equation for the gradient of the ‘best fit’ line ‘m’ is:

The least squares equation for the offset of the ‘best fit’ line ‘c’ is:

When interpreting these formulae you might like to be reminded that:

N

n

n N

x x x x x x

1

1 2 3 4

....

Although these formulae may initially look daunting, note that they contain some common terms, for example

note how many times

N

n

n

x

1

appears in the formulas above. By identifying such common terms you can perhaps

save effort by calculating them only once and use the results when those terms appear in later equations or writing

one function to do this and use it each time it’s needed.

Y Axis

X Axis

0

0

offset - c

Value of X

Value of Y

"Best fit"

straight line of

gradient m

U:\C\c-18-19\Tutorial\Assessed_Exercise_No_1\Assess-1-2018-19.docx - 3 - (? Peter Judd/University of Sheffield '98-'18)

2.2 How the program should appear to the user – the Requirements.

Reminder, the aim of this assessed exercise is for you to write a program that will allow the user to enter a set

of data (in the form of x, y pairs) and then uses the least squares technique to calculate and display the gradient

(m) and offset (c) of the “best fit” straight line through that set of data.

a) The program should begin by briefly announcing its purpose to the user.

b) Next it should ask the user how many pairs of data values (sets of x and y) he/she intends to input, only

permitting the user to choose numbers of pairs in the range from 4 to 20 pairs (that is the user should be

permitted to enter no fewer than 4 pairs and no more than 20 pairs).

c) Make sure your program displays clear instructions to the user at each stage so that the user knows exactly

what the program wants her (or him) to do.

d) The program should then ask the user to input the specified number of data value pairs, storing them in suitable

variable(s). Your program should be able to accept values for x and y entered as real numbers. Your program

should accept only positive numbers that are in the range between l000000.0 and 0.000005.

e) Next the program should neatly display all the data pairs entered in a tidy way on the screen.

f) The program should use the least squares formulae described section 2.1 above to process the set of data

entered and so calculate the values for ‘m’ and ‘c’ for the ‘best fit’ straight line through that set of data.

g) The program should then neatly display the values of ‘m’ and ‘c’ that it has calculated.

h) The program should then ask the user if he/she would like to repeat the program, interpret their reply, and, if

their answer is yes then the program should repeat again all steps from step b) onwards.

Please note:

When designing you program: be careful to ensure that it makes efficient use of variable space by choosing

suitable types for your variables that do not waste memory unnecessarily. Don’t just assume this program

will be compiled to run on a PC with the Dev-C compiler, make sure you use the smallest ‘C’ type variables

necessary according to the minimum sizes I gave for the standard C types in the lectures. Also make

appropriate use of the various flow-control statements 'C' has to offer to build loops where they would be

helpful.

I want you to divide your program up into separate functions. Programs that consist of everything inside the

single function main only will earn far fewer marks than programs that are divided into more than one

function.

2.3 A sample data set to use for testing

Here is some sample data upon which you might like to test your program:

First a simple set (you could try plotting it as a graph and estimating m and c by hand):

X Y

1.1 2.9

2.0 4.1

2.9 5.0

4.1 5.9

4.9 7.1

6.0 8.0

The results are: Gradient of best fit straight line m = 1.025 approx. with and a y intercept at c = 1.911 approx.

U:\C\c-18-19\Tutorial\Assessed_Exercise_No_1\Assess-1-2018-19.docx - 4 - (? Peter Judd/University of Sheffield '98-'18)

Now a more complex set:

X Y

103 65.9

2 x 103 122

3 x 103 187

4 x 103 256

5 x 103 314

6 x 103 358

7 x 103 457

8 x 103 482

9 x 103 582

104 635

The results are: Gradient of best fit straight line m = 0.0634 and a y intercept c at -2.907.

________________________________________________________________________________________

2.4 Some helpful hints

? Your program must be written in ‘C’ and not ‘C++’. (I teach ‘C’ in my lectures, not C++, so sticking to

techniques I have taught will mean you will be OK). Make sure you save your file with a ‘.c’ filename

extension NOT ‘.cpp’. When using Dev-C make sure when saving your file that the “Save File” dialogue

has the “Save as type” drop-down menu set for “C source files (*.c)”.

By the time this sheet is handed out you will have already covered, in lectures and tutorials, all the material

necessary to allow you to write a suitable program. However, future lectures and background reading of your

own may be of additional help.

Make your program code as easy to "read" (by a human) as possible. For example partition it (in other words

break it up) by making your own functions. (Programs that consist of everything inside the single function

main only will earn fewer marks than programs that are divided into more than one function). (See my example

solution to Lab 5 question 4 file TUT5Q4-4.c in the EEE125 MOLE course, in the ‘Lab Classes’ section, in

the ‘Lab Class Downloads’ folder and finally in the ‘Lab Sheet 5 – Downloads’ showing use of functions).

Use well-chosen identifiers for function names and variable names so that the purpose of a particular

function or variable is hinted by its name.

Make sure the program is well commented (i.e. using /* */ marks) so that the purpose of each part is clear.

These comments should be concise. Note: there is no need to use comments to explain how a particular ‘C’

construct works, you can assume the reader understands the ‘C’ language itself (e.g. you don’t need to explain

how a ‘for’ loop works as such). However you should add comments to explain what your program aims to

achieve with particular ‘C’ constructs where it isn't immediately obvious (e.g. explain what useful task a

particular ‘for’ loop is performing for you in your particular program). This is an important skill needed by

programmers to ensure their program code is ‘readable’ and ‘understandable’ by others who may have cause

to examine it or modify it later. I have given clear guidance in the lectures about how to lay out a program and

how to add comments – check your lecture slides to see what I said.

? Don't forget: planning your program thoroughly on paper first is by far the most effective way of quickly

writing a good program. Don't rush to coding at the PC too soon. Start by breaking the task down into

manageable portions, then plan the sequence of events for each portion with flow-charts and pseudo code etc.

Flow-charts in particular will help you identify the appropriate flow control statements ('while', 'do..while',

'for', 'if' etc.) to choose.

Test the output from your program by using various sets of data. You can generate your own test data quite

easily. Use a calculator or a spreadsheet to help verify your results. Don't forget to check your program's

behaviour with illegal data (i.e. data outside the range allowed for input), does it behave appropriately?

U:\C\c-18-19\Tutorial\Assessed_Exercise_No_1\Assess-1-2018-19.docx - 5 - (? Peter Judd/University of Sheffield '98-'18)

Don't forget, “divide and conquer” is a wise approach. Break the task down into manageable portions and

tackle them one at a time, don't try and code up the whole program in one go only to find it doesn't work. The

task of finding a fault (or more likely many faults) in a large program is like "looking for a needle in a haystack"

- make sure you have only a small "haystack" to search! Start off with a small program which only does the

first few steps of the task, get that working first. Next add a bit more to your program and get that working

too. Continue in this way until the program can carry out the complete task

Above all, be sure to hand something in by the hand-in date. If you examine my marking scheme carefully

(see later) you will see that only a small proportion of the marks are available for accuracy of results etc.

there are many more marks available for other aspects of the work I ask for. If you only manage to produce a

program that asks for, stores and re-displays the input sample data values but does not even attempt to do

anything else then I can at least give you some marks for that much (which is better than no marks if you hand

in nothing!)

If you need help:

a) Please talk to me or my demonstrators during a timetabled afternoon computer lab. session.

b) Be sure to make full use of the 'C' books in the library and the web links provided in our MOLE course.

c) If you still need help, email me to make an appointment to sit down with me "1 to 1". When you send such

an email be sure to suggest as many time-slots when you could be available to meet as you can so that I

have a good chance of finding a mutually convenient meeting time.

3 What should you hand in?

3.1 The program itself:

You should hand you ‘C’ program file itself in via MOLE (see instructions in section 3.2 below) and it

should be in the form of a source file of ‘C’ code (that is the ASCII text file created in the usual way by using

the Dev-C++ Editor when writing a program and saved with the filename and the file name extension for C

Source Files: “leastsq.c”). You MUST name the file “leastsq.c " Please use this name only, it helps

me process your work quickly. It must not be called “leastsq.cpp"! (*.cpp implies a C++ file and you

must not write in C++!)

You MUST write your Registration number into a comment string as the first line of your program like

this:

/* My Reg Number: 180113134 */

#include <stdio.h>

…and so on. You are NOT required to include your name.

If you choose to write and test your program using a `C' compiler other than the Bloodshed Dev-C environment

provided for you on the University's Computer network (as used in the lab. sessions) then I strongly

recommend that you bring the final version of your source code into the University and check it compiles and

runs correctly using the Dec-C compiler on the University's Computer network before handing it in. It is this

same Dev-C compiler environment that I will use to compile and test you program in order to assess it!

U:\C\c-18-19\Tutorial\Assessed_Exercise_No_1\Assess-1-2018-19.docx - 6 - (? Peter Judd/University of Sheffield '98-'18)

3.2 Submitting your file:

To submit your program via MOLE follow these instructions (follow them carefully as you only get one chance

to submit!):

a) You only have one chance to submit your file, once submitted you cannot change it, so be sure you are

finished and have chosen the correct file to submit and attach it correctly.

b) Once you have finished your C source file and you are happy that it is ready to submit it, open a web

browser and either login in to MOLE via MUSE or log in to MOLE directly as follows:

http://vista.shef.ac.uk/ and log in usual way

c) On the “EEE125 Programming” course home page look for the ‘Assessment and Feedback’ section in

the left-hand menu.

d) In the ‘Assessment and Feedback’ section of this left-hand menu you should see a heading called

‘Assessment’. Click on this.

e) You should now see an item titled “C Programming Course, Assessed Exercise No. 1”, make sure you

click on this title.

f) Scroll down to section “Assignment Submission”. DO NOT use the Create Submission button. Look

below and you will see a line beginning “Attach file” and a button marked “Browse My Computer”

Click on this. A file browser window should now open.

g) In the file browser window navigate to your folder and select your ‘C’ source file leastsq.c in the

conventional way. (Make absolutely sure you are selecting the C source file - the one you typed – not

any of the other associated files the compiler generates when you compile and run your program). To do

this, look at the icon displayed beside the file name, make sure you pick the file with the icon showing a

small blue ‘.c’ in the corner. Double click on your leastsq.c file to attach it. It should now appear in

a list of “Attached files”.

h) Once you are sure you have attached your leastsq.c file then scroll to the bottom of the page and you

should see the Submit button on the right hand side, click this button to submit your work. Note: You

must NOT write anything in the Add Comments box (I will not read anything placed here).

U:\C\c-18-19\Tutorial\Assessed_Exercise_No_1\Assess-1-2018-19.docx - 7 - (? Peter Judd/University of Sheffield '98-'18)

3.3 Marking Scheme

Here is the marking scheme I will use to mark your work. Initially, as you can see, I will mark out of 100, “full

marks” would be 100%.

Aspect Comment Mark

Overall

Program

Design

Does the program try to meet the specification laid out in this

sheet? Is it designed to do all the things asked for?

20

Choice of

Variables

Have variables been created using appropriate types and do they

make efficient use of storage space?

5

Quality of `C'

code

Have the many useful ‘C’ language features discussed in

lectures and tutorials been exploited? Are the ‘C’ constructs

used appropriately?

10

Readability of

code

Is the program's purpose easily understood from the way it's

structured e.g. does it have an appropriate hierarchical form

(exploiting functions?). Is it well (concisely and clearly)

commented? Have sensible, self explanatory, identifiers been

chosen for function names and variable names?

5

Use of

Functions

Have user functions other than main been written at all? Are

they used sensibly? Is the choice of return types and parameters

sensible?

20

Compile &

Run

Does the program compile without errors or serious warnings?

Does it run without crashing etc?

10

Accuracy of

results

Are the results it produces correct? 20

User interface Does the "user interface" clearly inform the user what she or he

must do at each stage? Are the outputs presented clearly and in

an appropriate fashion?

10

Total 100

4 Unfair Means

The basic principle underlying assessed work is that the work submitted for assessment must be entirely

your own. No one objects to you discussing the principles of C programming in general with others, but:

plagiarism and collusion are not allowed. You must not discuss the details of how to do this exercise with any

one other than Peter Judd or one of his programming lab. demonstrators. In the context of this exercise, unfair

means would include:

1 You MUST NOT allow anyone else to write or dictate to you your program, in whole or in part.

2 You MUST NOT look at someone else’s program for this exercise or copy from someone else’s work or

exchange emails or internet chat messages (MSM, Weibo, Whatsapp, Facebook or similar) with someone

else which include code from either your program or their program for this exercise. Note: this includes with

the lab. Demonstrators or students in other years.

3 Likewise you MUST NOT write program code for, or share program code with, another student on this

course or from previous years of study or anyone else.

4 You MUST NOT team up with others to write one program (in whole or in part) together, then all hand in

programs containing that same code (in whole or in part).

5 You MUST NOT copy portions of code from any sources (that are not of your own creation) such as a

website or a book or from someone else’s computer, website (even from a website where the language is not

English) or memory device. (However: I grant you exceptional permission to copy from any of the

U:\C\c-18-19\Tutorial\Assessed_Exercise_No_1\Assess-1-2018-19.docx - 8 - (? Peter Judd/University of Sheffield '98-'18)

examples of code that I have given to you during this course as lecture or tutorial examples – if you do

this, then attribute the source of those portions of code to me by writing my name in a comment like this /*

taken from Peter Judd’s examples */ immediately before and immediately after the code

concerned.)

Remember: the basic principle underlying assessed work such as this is that the work submitted for

assessment must be entirely your own. We wish to only give marks for programs written by you alone!

If you are in any doubt about what might constitute unfair means in the context of this exercise then please

discuss any areas of uncertainty with me. If you experience any problems with this assignment then seek help

from me or the demonstrators present during lab. sessions.

Please note: I will be using a sophisticated program specially designed to detect plagiarism in a set of ‘C’

programs to help me detect evidence of such unfair means in the assessed work that you hand in, so, please

don't take the risk of copying work, submit only work done by you entirely on you own. Where I suspect unfair

means to have been used, the department reserves the right to give zero marks to all individuals concerned

and/or refer you to the University Discipline Committee and/or place a note in your student record file

(We have caught people breaking these recommendations before and done all these things, so do please note the

warning!).

Good Luck! Peter Judd