Understanding Bit, Nibble and Byte in this article explained Bit , Nibble and Byte Data storage format of hard disk with how to calculate it.
Bit
A bit, short for binary digit is the smallest unit of data or basic information unit in computing and digital communications. It can contain only one of the two values represented as 0 or 1. They also represent logical values such as true/false, yes/no, activation states (on/off), algebraic signs (+/-) or any other two-valued attribute.
Byte
A byte, short for binary term is a digital information unit of data that consists of eight bits. The byte is representation of the number of bits a system has used to encode one text character. Therefore, it is the smallest addressable memory unit in many computer architectures. Two hexadecimal digits represent a full byte or octet.
Nibble
A nibble, also known as half-byte or tetrade is a collection of four bits or half of an octet in computing. Common representation of a byte is two nibbles.
Related Product : Computer Hacking Forensic Investigator | CHFI
Hard Disk Data Addressing
Hard disk data addressing is the technique of assigning addresses to physical blocks of data on the hard drives. There are two types of hard disk data addressing:
1. CHS (Cylinder-Head-Sector)
This process identifies individual sectors on a hard disk according to their positions in a track, and the head and cylinder numbers determine these tracks. It associates information on the hard drive by specifications such as head (platter side), cylinder (radius), and the sector (angular position).
2. LBA (Logical Block Address)
It addresses data by allotting a sequential number to each sector of the hard disk. The addressing mechanism specifies the location of blocks of data on computer storage devices and secondary storage systems such as hard disk drives, SCSI, and enhanced IDE drives. This method does not expose the physical details of the storage device to the operating system.
Data Densities on a Hard Disk
Hard disks store data using the zoned bit recording method, which is also known as multiple-zone recording. In this technique, tracks form a collection of zones depending on their distance from the center of the disk and the outer tracks have more sectors on them than the inner tracks. This allows the drive to store more bits in each outer track compared to the innermost zone and helps to achieve a higher total data capacity.
1. Track Density
It refers to the space a particular number of tracks require on a disk. The disks with greater track density can store more information as well as offer better performance.
2. Areal Density
It refers to the number of bits per square inch on a platter and it represents the amount of data a hard disk can hold.
3. Bit Density
It is the number of bits a unit length of track can accommodate.
Also Read : Tracks & Advanced Format of Sectors
Disk Capacity Calculation
Calculate
A disk drive that has:
- 16,384 cylinders
- 80 heads
- 63 sectors per track
Assume a sector has 512 bytes. What is the capacity of such a disk?
Answer : The conversion factors appropriate to this hard disk are
- 16,384 cylinders / disk
- 80 heads / cylinder
- 63 sectors / track
- 512 bytes / sector
Solution
Total bytes = 1 disk * (16,384 cylinders / disk) * (80 heads / cylinder) (1 track / head) * {63 sectors / track) * (512 bytes / sector) = 42,278,584,320 bytes 1 Kilobyte (KB) = 2^10 bytes = 1,024 bytes
1 Megabyte (MB) = 2^20 bytes = 1,048,576 bytes = 1,024 KB
1 Gigabyte (GB) = 2^90 bytes = 1073,741,824 bytes =1,048,576 KB = 1,024 MB
1 Terabyte (TB) = 2^40 bytes = 1,099,511,627,776 bytes = 1,073,741,824 KB = 1,048,576 MB= 1,024 GB
Using these definitions, express the result in GB as:
42,278,584,320 bytes / {1,073,741,824 bytes / GB) = 39.375 GB
Hard disk in a typical computer system has a storage capacity. Data is stored on the hard disk in the form of files.
A file is nothing more than a collection of bytes. The bytes may be:
- ASCII code
- Instruction of a software program for the computer system to execute
- Record of a database
- Pixel colors for a GIF image
Measuring good hard disk drive performance includes calculation of it two characteristics including the access time and data transfer rate.
Access time
Access time refers to the time a drive takes to initiate the data transfer. The controlling factors of this time on a drive depend on the mechanical nature of rotating disks and moving heads.
The main components added to get the access time are:
- Seek time: The time a hard disk controller requires to find a particular data. When required to read or write data, the disc heads move to the correct position through the process of seeking. The time it takes to move read or write disc heads from one point to another of the disk is the seek time. Common seek time is between 10 to 20 milliseconds, with common desktop type normally being around 9 milliseconds.
- Rotational latency: It refers to the rotational delay the chosen disk sector takes to rotate under read or write disk drive heads. The average disk rotational latency is half of the time the disk takes to make one revolution. The term is applicable only to rotating storage devices like hard disk drives and floppy drives but not tape drives.
- Data transfer rate: The data transfer rate of a drive is expressed by internal rate, which is the data moving between the disk surface and the drive controller as well as the external rate, which is the data moving between the drive controller and the host system. The host transfer rate or data transfer rate is the speed at which host computer can transfer data from the IDE/EIDE or SCSI interface to CPU.
- Inner zones’ data transfer rates range from 44.2 MB/s to 74.5 MB/s
- The transfer rate at the outer zone is 74,0 MB/s to 111.14 MB/s
Questions related to this topic
- Is 1gb equal to 1024 MB or 1000 MB?
- What is GB KB MB and bytes?
- Is a kilobyte 1000 or 1024 bytes?
- Why is 1kb equal to 1024 bytes?
- What is Bit Nibble and Byte?
This Blog Article is posted by
Infosavvy, 2nd Floor, Sai Niketan, Chandavalkar Road Opp. Gora Gandhi Hotel, Above Jumbo King, beside Speakwell Institute, Borivali West, Mumbai, Maharashtra 400092
Contact us – www.info-savvy.com
