SHELL

0. Initialization
0a. Create shared memory buffer.

1. Reads user input.

2. Attempts to map user input to a command.
2a. Tokenize input string.
2b. Match initial token to process name.

3. If command can be matched to a process name
3a. Fork off child process, execute command.
3b. Wait for child process to complete.

4. Return to step 1.

FAT HELPERS

boolean readFATData(unsigned int, byte*)
* Reads data mapped from the FAT to the data sector into a buffer.
* Returns if the data was read successfully.

boolean writeFATData(unsigned int, unsigned int, byte*)
* Writes the given buffer with the given sector size to the given FAT chain, resizing if necessary.
* Returns if the data was written successfully.

boolean getNextFreeFAT(unsigned int*)
* Writes the next free FAT entry into the given integer.
* Returns if any FAT entries were free.

boolean resizeFAT(unsigned int, unsigned int)
* Resizes the given FAT chain to the given length.
* Returns if it was able to do so.

void clearFAT(unsigned int)
* Clears the given FAT chain.

ENVIRONMENT VARIABLES

typedef byte EnvVarName
* key indicating the environment variable to use.

boolean envCreate()
* Allocates a shared memory block to house our environment variables.
* Returns if the block was successfully allocated.

void envDestroy()
* Deallocates the shared memory block.

boolean envConnect()
* Connects the given process to the shared memory block.
* Returns if the connection was successfully made.

boolean envGet(EnvVarName, char*)
* Reads the contents of the given environment variable into a buffer.
* Returns if the environment variable was successfully retrieved.

void envSet(EnvVarName, char*)
* Writes the contents of a buffer to the given environment variable.

boolean envDefined(EnvVarName)
* Returns if the given environment variable has been defined.

void envUndefined(EnvVarName)
* Clears the given environment variable.

Memory Block Layout
* Per Variable - 128 bytes
* Accessing a variable: block[varName * 128]
* If not defined, block[varName * 128] == '\0'

Environment Variables
* DISC - current data file
* PWD - present working directory

DIRECTORY ENTRIES

struct directoryEntry_t
* Maps to directory entry memory layout.

directoryEntry_t* getDirectoryEntryFromIndex(unsigned int, byte*)
* Retrieves the directory entry at the given index in the directory data.

directoryEntry_t* getDirectoryEntryFromName(char*, byte*)
* Retrieves the directory entry with the given name in the directory data.

boolean getDirectoryEntryIsDeleted(unsigned int, byte*)
* Returns if the given directory entry has been deleted.

boolean getDirectoryEntryIsEmpty(unsigned int, byte*)
* Returns if the given subdirectory entry is empty, or FALSE if the entry is not a subdirectory.

unsigned int removeDirectoryEntryByIndex(unsigned int, unsigned int, byte*)
* Removes the directory entry at the given index from the data.
* Returns the number of sectors remaining

PATH UTILS

void resolvePath(char*);
* Take in the relative path and add it to our current path from shared memory.

COMMANDS
cat x
* Change the path to an absolute path if it is relative using resolvePath
* Get the directory entry from the name argument using getDirectoryEntryFromName
* Get the first logical cluster from the directory entry
* Read the data using the read fat function

cd x
* If not given an argument change our shared current directory to a constant home directory
* Change the path to an absolute path if it is relative using resolvePath
* From name function to check if the directory exist
* If it does exist change our current directory in shared memory to the resolved path.

df
*

ls x
* If there is no argument given set the argument to the current path from the shared memory
* Change the path to an absolute path if it is relative using resolvePath
* Get the directory entry from the name argument using getDirectoryEntryFromName
* If the file is not a subdirectory we write out the data about the file from the directory entry
* If the file is a subdirectory we retrieve the directory info for that subdirectory
	* All the valid directory entries within the subdirectory
	* Write out information about all of these entries

pwd
* print the current directory from shared memory

rm x
* If there is no argument or more then one argument  print an error message and quit
* Change the path to an absolute path if it is relative using resolvePath
* Get the directory entry from the name argument using getDirectoryEntryFromName
*