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--- user:mowens3:portfolio:cprogproject1 [2012/02/14 21:19] – [Project: SECRET AGENT] mowens3
+++ user:mowens3:portfolio:cprogproject1 [2012/02/29 00:37] (current) – [Project: SECRET AGENT] mowens3
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+======Project: SECRET AGENT======
+A project for C++ by Michael during the Spring 2012.
+This project was begun on feb 14 and is anticipated to take 2 weeks to complete. Project was completed on Feb 28th, 2012
+=====Objectives=====
+We are making an encoder and decoder in C.
+=====Prerequisites=====
+In order to successfully accomplish/perform this project, the listed resources/experiences need to be consulted/achieved:
+  * successful completion of project #0 and solid understanding of pertinent topics
+  * familiarity with memory allocation via **malloc(3)**
+  * familiarity with looking up C function parameters/information in the manual
+  * familiarity with if statements, especially in use for error detection
+  * familiarity with pointers and pointer arithmetic
+  * familiarity with loops
+  * file I/O
+=====Background=====
+Writting a program that will encode a text file by chagning the characters.\\
+A different file will decode a text file by reversing the change in characters. \\
+It asks for a cypher key, and you will need to know that key when you decode it.
+=====Scope=====
+This project will test your familiarity with more involved algorithms, storage, and control structures.
+Encoding is the process of converting a message into a coded form.
+Decoding is the reverse- retrieving that original message from an encoded form.
+In this project you will write a 2 programs: one that will take a plain text message and convert it into a coded form (largely indecipherable to the regular english expecting eye) using a given cipher key, and another that will reverse the process (or decipher), when given the appropriate key.
+The key is a numeric used to rotate the alphabet a set amount. Where A would normally equal 1, and Z 26, using a cipher key of 1 to shift 1 position to the right; A would now equal 2 (or B), B is now 3 (or C), and Z would be 1 (A).
+Your encoding program can operate as follows:
+  * obtains its cipher key from a text file called "key.txt"
+  * or, if you prefer, use command-line arguments to provide the key
+  * obtains the input message from a file called "message.txt"
+  * if "plain.txt" is blank, or does not exist, the program should prompt the user to enter the message via STDIN
+  * outputs the ciphertext message to STDOUT **AND** saves it to a file called "cipher.txt"
+  * implement error checking to avoid segfaults
+The decoding operation is essentially the reverse (shifting to the left). I'd suspect you could reuse much of the same logic.
+Your decoding program:
+  * obtains its cipher key from a text file called "key.txt"
+  * or, if you prefer, use command-line arguments to provide the key
+  * obtains the input cipher from a file called "cipher.txt"
+  * if "cipher.txt" is blank, or does not exist, the program should prompt the user to enter the message via STDIN
+  * outputs the plaintext message to STDOUT **AND** saves it to a file called "plain.txt"
+  * implement error checking to avoid segfaults
+If you want, you may implement both functionalities into one program so long as you provide a mechanism for the user to access both operations (but note this is not required for successful completion of this project).
+=====Code=====
+The encipher code:
+<code c>
+/*encodes*/
+#include<stdio.h>
+#include<stdlib.h>
+int main()
+{
+	FILE *original, *encoded;
+	int key = 0; //number of asci spaces moved
+	int holder = 0; //used as a temp space holder
+	char letter;
+	original = fopen("file2.txt","r");
+	encoded = fopen("encoded.txt","w");
+	printf("Please pick your encyphering number: ");
+	scanf("%d",&key);
+	letter = fgetc(original);
+	while(letter !=  EOF)
+	{
+		if ((letter >='A') && (letter <= 'Z'))
+		{
+			holder = letter - 65;
+			holder = holder + key;
+			holder = holder % 26;
+			letter = holder + 65;
+		}
+		if ((letter >= 'a') && (letter <= 'z'))
+		{
+			holder = letter - 97;
+			holder = holder + key;
+			holder = holder % 26;
+			letter = holder + 97;
+		}
+		fprintf(encoded, "%c", letter);
+		letter = fgetc(original);
+	}
+	printf("Encoding complete\n");
+	fclose(original);
+	fclose(encoded);
+	return(0);
+}
+</code>
+Deciphering code.
+<code c>
+//decodes
+#include<stdio.h>
+#include<stdlib.h>
+int main()
+{
+	FILE *encoded, *decoded;
+	char typed;
+	int key = 0;
+	char letter;
+	unsigned char holder = 0;
+	encoded = fopen("encoded.txt", "r");
+	decoded = fopen("decoded.txt", "w");
+	printf("Please enter the original key number: ");
+	scanf("%d", &key);
+	letter = fgetc(encoded);
+	while(letter != EOF)
+	{
+		if ((letter >= 'A') && (letter <= 'Z'))
+		{
+			holder = letter - 65;
+			holder = holder - key - 230;
+			holder = holder % 26;
+			letter = holder + 65;
+		}
+		if ((letter >= 'a') && (letter <= 'z'))
+		{
+			holder = letter - 97;
+			holder = holder - key - 230;
+			holder = holder % 26;
+			letter = holder + 97;
+		}
+		fprintf(decoded, "%c", letter);
+		letter = fgetc(encoded);
+	}
+	printf("Decoding complete, check decoded.txt \n");
+	fclose(encoded);
+	fclose(decoded);
+	return(0);
+}
+</code>
+=====Execution=====
+An example run of the enciphering process:
+<cli>
+Please pick your encyphering number: 4
+Encoding complete
+</cli>
+Example run of the decoding process:
+<cli>
+Please enter the original key number: 4
+Decoding complete, check decoded.txt
+</cli>
+=====Reflection=====
+I learned that this project was a pain in the butt.  I also know, I don't want to mess with stuff like this again.  It gave me a headache trying to figure it out, and I don't think I could easly rewrite this program.
+=====References=====
+In this project, I had a lot of help from Matt, our teacher.  I had so many issues that I couldn't figure out why they were happening.

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