Computer Programming HW 04 Solution

Q1
Q2
Q3








Points
30 points
20 points
50 points








Read General rules at the end of homework and make sure that you named files correctly.




Q1)
GTU Encoding Table
Assume that we are in a terrible science war. All universities sniff




Char
Code


each other’s network and try to understand what they are doing.




E
0




In the cold science war you are expected to send messages not as




I
10




plain text but as encrypted text.




Space
110












T
1110




Yes, you are the chosen one and all you have and need is GTU




C
11110




encoding table and your amazing coding skills! Table is given








left… Note that it only includes a part of the alphabet. The




N
111110












remaining characters are not going to be encrypted.




A
1111110
















G
11111110
Objectives




B
111111110




1. Read the plain text message from PlainMessagesToSent.txt




Z
1111111110






file




H
11111111110






2.
Write the encoded message to EncodedMessages.txt file




L
111111111110




3.
Crypt encoded messages by reading encoded messages file




U
1111111111110






and changing each ‘1’ with ‘*’ and ‘0’ with ‘_’, also add ‘-‘




V
11111111111110








symbol according to following rule:




R
111111111111110








Add a ‘-‘ symbol after each M characters. M starts with N and




S
1111111111111110








decreased by one after adding a ‘-‘ symbol until M is equal to




Y
11111111111111110








zero. When M is equal to zero reinitialize it by N. N is given to




























be 5.












4.
Write the encrypted message (encrypted by ‘*’ ‘_’ ‘-‘) to














EncryptedMessages.txt file


Example
























Plain Text Message


IT IS BAG






Encoded Message


101110110101111111111111110110111111110111111011111110


Encrypted Message


*_***-_**_-*_*-**-*-*****-****-**_-**-_-*****-***_-***-**-*-_****-***_-



Big Picture























CALL




OPEN FILES IN MAIN


encode_and_write_


ENCODING
SEND FILE* TO


to_file(…) IN


encode_message(…)


encode_message










function


function to encode








a character































OPEN FILES IN MAIN




SEND FILE* TO

ENCRYPTION crypt_message(…)




function
GIVEN
ASKED FOR
Template_1.c
Part1.c
PlainMessagesToSent.txt
EncodedMessages.txt


CryptedMessages.txt



Note that you are expected to use Template_1.c file for Q1 which is attached to homework. You are going to find detailed info there also.




Q2) In this question, you are expected to read an encrypted message and convert it back to the plain text message.




Objectives

Read the encrypted message from EncryptedInput.txt which is attached to homework.



Eliminate ‘-‘ symbols and change ‘*’ to ‘1’ and ‘_’ to ‘0’ to obtain the encoded message. Write encoded message to EncodedInput.txt file.
Read the encoded input from EncodedInput.txt file.
Decode the encoded message and write the plain text message to ReceivedMessage.txt file.



Big Picture













OPEN FILES IN MAIN




SEND FILE* TO




DECRYPTION decrypt_message(…) function





























CALL




OPEN FILES IN MAIN


decode_and_write_


DECODING
SEND FILE* TO


to_file(…) IN


decode_message(…)


decode_message










function


function to decode








a character



























GIVEN
ASKED FOR
Template_2.c
Part2.c
CryptedInput.txt
EncodedInput.txt


ReceivedMessage.txt



Note that you are expected to use Template_2.c file for Q2 which is attached to homework. You are going to find detailed info there also.




Q3) Now it is time to decode X University’s messaging system! Assume X University uses a heuristic to create encoding table. Their heuristic is just based on frequency of letters. Frequently used letters have shorter code length.




Example

Character List
A B C






Sample
AABABAABCBAAC


Frequency List of Sample
Char
A
B
C
Counts
7
5
2


Encoding Table of Sample
Char
A
B
C
Code
0
10
110


Encoded Message of X University
11010010011000110


Plain Text Message of X University
CBABACAAC




Objectives




You are given CharacterList.txt including three characters which are the letters of messaging system’s alphabet. However, since the file is recovered from their trash it is broken (it contains some extra characters which are not a part of their alphabet). You should ignore all characters which are not letter like ‘!’, ‘=’,’+’ etc. Write a function to figure out three letters and return number of letters read.



Read the file Sample.txt and count letters to find their frequencies and sort the letters with respect to their frequencies. Implement swap functions given in template c file. You are going to use swap functions while sorting numbers and characters.



Since you figured out frequency of letters thanks to count letters function, you can handle decoding process. Decode the messages in XUniversityEncoded.txt file. Write the decoded (plain text) message to XUniversityMessage.txt file



Big Picture

















LEARNING
READ CharacterList to


READ Sample to learn


learn letters of


encoding codes of








ALPHABET
alphabet


letters































OPEN FILES IN MAIN

SEND FILE* TO

DECODING decode_message(…)




function






GIVEN
ASKED FOR
Template_3.c
Part3.c
CharacterList.txt
XUniversityMessage.txt
Sample.txt


XUniversityEncoded.txt





Note that you are expected to use Template_3.c file for Q3 which is attached to homework. You are going to find detailed info there also.




General:

Obey honor code principles.
Obey coding convention.



Read your homework carefully and follow the directives about the I/O format (data filenames, file formats, etc.) and submission format strictly. Violating any of these directives will be penalized.



Your submission should include the following file and NOTHING MORE (no data files, object files, etc):



HW04_<student name_<student surname_<student number_part1.c




HW04_<student name_<student surname_<student number_EncodedMessages.txt HW04_<student name_<student surname_<student number_CryptedMessages.txt HW04_<student name_<student surname_<student number_part2.c HW04_<student name_<student surname_<student number_EncodedInput.txt HW04_<student name_<student surname_<student number_ReceivedMessage.txt HW04_<student name_<student surname_<student number_part3.c HW04_<student name_<student surname_<student number_XUniversityMessage.txt

Do not use non-English characters in any part of your homework (in body, file name, etc.).
Deliver the printout of your work until the last submission date.