There Are 4 Parts For The Project The Question May Be Long To Read Bu
The project comprises four parts, each requiring implementation of classes and functions to simulate a disk drive, manage files and directories, create a shell interface, and develop a database system. The first part involves creating a class Sdisk
to emulate a disk drive with specified blocks and block sizes, handling file creation, reading, and writing with strict adherence to specifications. The second part extends this by developing a Filesys
class to manage a file system on the disk, including directory and File Allocation Table (FAT) management, with functions for creating, deleting, reading, and writing files and blocks. The third part introduces a Shell
class to interact with the file system, providing commands like listing directories, adding or removing files, and copying files. The fourth and final part involves creating a Table
class for a database system that reads records from a data file, builds indexed files, and allows searching records by date, utilizing the underlying file system for storage and retrieval.
Paper For Above instruction
The comprehensive system being developed in this project requires a layered and modular approach, starting from basic disk simulation to complex database management. Each part builds upon the previous, emphasizing object-oriented design principles, proper file management, and efficient data access methods.
Part 1: Disk Drive Simulation with Sdisk Class
At the core of this project is the Sdisk
class, which replicates a physical disk drive using a file stored on the host system. The class is designed with three primary attributes: the disk's filename, the number of blocks, and the block size in bytes. Its
constructor initializes the disk, either by opening an existing file or creating a new one. When creating a new disk, the file is filled with a total of numberofblocks * blocksize characters, representing the raw disk memory.
The constructor further checks if the file exists to determine whether it represents a pre-existing disk. If the file exists, it is opened and treated as a disk. Otherwise, a new file is created with the appropriate size. The getblock
method retrieves a given block from the disk, validating the block number and copying data into the provided buffer. Conversely, the putblock method writes data from the buffer into the specified block. Both methods return status codes indicating success or failure.
This class encapsulates the direct interaction with the disk, ensuring that only these methods perform actual file operations. This encapsulation promotes data integrity, avoids corruption, and provides a clear interface for higher-level file system management.
Part 2: File System Management with Filesys Class
The next layer, the Filesys class, extends the Sdisk
class to implement a simple, yet functional, file system. This encompasses managing directories (ROOT) and a File Allocation Table (FAT), which track the storage and organization of files. The class initiates by examining the underlying disk to determine if a file system already exists, reading the FAT and ROOT from the disk if so. If not, it creates and initializes these structures, preparing the disk for file operations. The
method reads raw data from an input file and populates the file system, creating index records for quick access. It constructs the ROOT directory, holding file names and first block numbers, and a FAT which maintains pointers from one block to the next within a file, as well as managing free space.
Other essential functions include fssynch
, which writes changed FAT and ROOT data back to the disk immediately to ensure data consistency; fsclose , to finalize changes; and file operations such as newfile , rmfile , addblock , delblock , and readblock
. These manipulate files at the block level, updating tables correspondingly.
A key question in this part is determining the size of the FAT in blocks, which depends on the total number of blocks in the disk. Since each FAT entry must be stored in decimal digits (0-9), the size of the FAT array in blocks is governed by the total number of entries and the size of each entry. The value of fatsize
should be calculated to sufficiently store all entries, considering each entry as a decimal number requiring
one byte, and the total number of entries equals the total number of blocks on the disk.
Part 3: Command Line Shell Interface through Shell Class
The third part introduces a Shell class, which provides an interactive interface to navigate and manipulate the file system. It inherits from Filesys and offers functions such as dir to list all files, add and del to create or delete files, type to display contents, and copy to duplicate files.
The shell class encapsulates user commands, enabling manipulation of the underlying storage structures via straightforward function calls. For example, the dir command will parse the ROOT directory and list all stored files, while add will prompt for input or accept parameters to create a new file entry and allocate its initial blocks in the FAT. Similarly,
removes files if they are empty, and type
displays the contents of a specified file by reading associated blocks.
This command-driven approach simplifies user interactions with the file system, facilitating testing and demonstration of the underlying functions.
Part 4: Database System with Table Class
The final component involves creating a Table
class that utilizes the file system for persistent storage of data records pertinent to Art History. Records are read from a structured text file, where each record contains fields such as date, end, type, place, reference, and description. The
Build_Table
method reads these records, stores them in a flat file, and simultaneously creates an index file keyed by the date for rapid searching.
The class manages two files: the data file (flatfile) containing full records, and the index file (indexfile) comprising key-index pairs of dates and block numbers. Record insertion involves parsing the input data, saving the record in a free block, and updating the index with the date and block number. The Search
function allows retrieval of records by date, utilizing the index file to directly locate the associated block, then reading and displaying the record.
This approach ensures efficient storage and retrieval, reducing search times via indexing while maintaining the structural integrity of the underlying file system.
In conclusion, this multi-tiered system demonstrates object-oriented principles, combining disk simulation, file management, user interface, and data indexing to build a simplified database system. Each part emphasizes encapsulation, modularity, and correctness, providing a comprehensive educational experience
about filesystem architecture and data management techniques.
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