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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.
GTU Encoding Table
Assume that we are in a terrible science war. All universities sniff each other’s network and try to understand what they are doing. In the cold science war you are expected to send messages not as plain text but as encrypted text.
Yes, you are the chosen one and all you have and need is GTU encoding table and your amazing coding skills! Table is given left… Note that it only includes a part of the alphabet. The remaining characters are not going to be encrypted.
Objectives
1. Read the plain text message from PlainMessagesToSent.txt
file
2. Write the encoded message to EncodedMessages.txt file
3. Crypt encoded messages by reading encoded messages file and changing each ‘1’ with ‘*’ and ‘0’ with ‘_’, also add ‘-‘ symbol according to following rule:
Add a ‘-‘ symbol after each M characters. M starts with N and decreased by one after adding a ‘-‘ symbol until M is equal to 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
Char
Code
E
0
I
10
Space
110
T
1110
C
11110
N
111110
A
1111110
G
11111110
B
111111110
Z
1111111110
H
11111111110
L
111111111110
U
1111111111110
V
11111111111110
R
111111111111110
S
1111111111111110
Y
11111111111111110
Q1)
Example
Plain Text Message
IT IS BAG
Encoded Message
101110110101111111111111110110111111110111111011111110
Encrypted Message
*_***-_**_-*_*-**-*-*****-****-**_-**-_-*****-***_-***-**-*-_****-***_-
Big Picture
ENCODING
OPEN FILES IN MAIN SEND FILE* TO encode_message(…) function
CALL encode_and_write_ to_file(…) IN encode_message function to encode
a character
ENCRYPTION
OPEN FILES IN MAIN SEND FILE* TO 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
1. Read the encrypted message from EncryptedInput.txt which is attached to homework.
2. Eliminate ‘-‘ symbols and change ‘*’ to ‘1’ and ‘_’ to ‘0’ to obtain the encoded message. Write
encoded message to EncodedInput.txt file.
3. Read the encoded input from EncodedInput.txt file.
4. Decode the encoded message and write the plain text message to ReceivedMessage.txt file.
Big Picture
DECRYPTION
OPEN FILES IN MAIN SEND FILE* TO decrypt_message(…) function
DECODING
OPEN FILES IN MAIN SEND FILE* TO decode_message(…) function
CALL decode_and_write_ to_file(…) IN decode_message 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.
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
Example
Objectives
1. 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.
2. 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.
3. 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 ALPHABET
READ CharacterList to learn letters of alphabet
READ Sample to learn encoding codes of letters
DECODING
OPEN FILES IN MAIN SEND FILE* TO 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:
1. Obey honor code principles.
2. Obey coding convention.
3. 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.
4. 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
5. Do not use non-English characters in any part of your homework (in body, file name, etc.).
6. Deliver the printout of your work until the last submission date.
