What is a hard disk drive? .
In computing, a compiler is a computer program that translates computer code written in one programming language (the source language) into another language (the target language). The name “compiler” is primarily used for programs that translate source code from a high-level programming language to a lower level language (e.g. assembly language, object code, or machine code) to create an executable program.: p1 
There are many different types of compilers which produce output in different useful forms. A cross-compiler produces code for a different CPU or operating system than the one on which the cross-compiler itself runs. A bootstrap compiler is often a temporary compiler, used for compiling a more permanent or better optimised compiler for a language.
Related software include, a program that translates from a low-level language to a higher level one is a decompiler ; a program that translates between high-level languages, usually called a source-to-source compiler or transpiler. A language rewriter is usually a program that translates the form of expressions without a change of language. A compiler-compiler is a compiler that produces a compiler (or part of one), often in a generic and reusable way so as to be able to produce many differing compilers.
A compiler is likely to perform some or all of the following operations, often called phases: preprocessing, lexical analysis, parsing, semantic analysis (syntax-directed translation), conversion of input programs to an intermediate representation, code optimization and code generation. Compilers generally implement these phases as modular components, promoting efficient design and correctness of transformations of source input to target output. Program faults caused by incorrect compiler behavior can be very difficult to track down and work around; therefore, compiler implementers invest significant effort to ensure compiler correctness.
Compilers are not the only language processor used to transform source programs. An interpreter is computer software that transforms and then executes the indicated operations.: p2 The translation process influences the design of computer languages, which leads to a preference of compilation or interpretation. In theory, a programming language can have both a compiler and an interpreter. In practice, programming languages tend to be associated with just one (a compiler or an interpreter).
What is a hard disk drive?
A computer hard disk drive (HDD) is a non-volatile data storage device. Non-volatile refers to storage devices that maintain stored data when turned off. All computers need a storage device, and HDDs are just one example of a type of storage device.
HDDs are usually installed inside desktop computers, mobile devices, consumer electronics and enterprise storage arrays in data centers. They can store operating systems, software programs and other files using magnetic disks.
More specifically, hard disk drives control the reading and writing of the hard disk that provides data storage. HDDs are used either as the primary or secondary storage device in a computer. They are commonly found in the drive bay and are connected to the motherboard via an Advanced Technology Attachment (ATA), Serial ATA, parallel ATA or Small .
Why do computers need hard disks?
Storage devices like hard disks are needed to install operating systems, programs and additional storage devices, and to save documents. Without devices like HDDs that can retain data after they have been turned off, computer users would not be able to store programs or save files or documents to their computers. This is why every computer needs at least one storage device to permanently hold data as long as it is needed.
How do hard disk drives work?
Most basic hard drives consist of several disk platters — a circular disk made of either aluminum, glass or ceramic — that are positioned around a spindle inside a sealed chamber. The platter spins with a motor that is connected to the spindle. The chamber also includes the read/write heads that magnetically record information to and from tracks on the platters using a magnetic head. The disks also have a thin magnetic coating on them.
The motor spins the platters at up to 15,000 rotations per minute. As the platters spin, a second motor controls the position of the read and write heads that magnetically record and read information on each platter.
Hard disk drive storage capacity
Some of the most common storage drive capacities include the following:
16 GB, 32 GB and 64 GB. This range is among the lowest for HDD storage space and is typically found in older and smaller devices.
120 GB and 256 GB. This range is generally considered an entry point for HDD devices such as laptops or computers.
500 GB, 1 TB and 2 TB. Around 500 GB and above of HDD storage is typically considered decent for an average user. Users can most likely store all their music, photos, videos and other files with this much space. Individuals with games that take up a lot of space should find 1 TB to 2 TB of HDD space suitable.
More than 2 TB. Anything over 2 TB of HDD space is suitable for users who work with high-resolution files, who need to store or house a large amount of data, or who want to use that space for backup and redundancy.
Hard drive components and form factors
Hard disk drive components include the spindle, disk platter, actuator, actuator arm and read/write head. Even though the term can refer to the unit as a whole, the term hard disk is the set of stacked disks — in other words, the part of the HDD that stores and provides access to data on an electromagnetically charged surface
The HDD form factor refers to the physical size or geometry of the data storage device. HDD form factors follow a set of industry standards that govern their length, width and height, as well as the position and orientation of the host interface connector. Having an industry-standard form factor helps determine a common compatibility with different computing devices
The most common form factors for HDDs in enterprise systems are 2.5-inch and 3.5-inch — also known as small form factor (SFF) and large form factor (LFF). The 2.5-inch and 3.5-inch measurements represent the approximate diameter of the platter within the drive enclosures.
While there are other form factors, by 2009, manufacturers discontinued the development of products with 1.3-inch, 1-inch and 0.85-inch form factors. The falling price of flash made these other form factors almost obsolete. It is also important to note that while nominal sizes are in inches, actual dimensions are specified in millimeters.
Many solid-state drives (SSDs) are also designed for the HDD form factor. SSDs that fit into the same slots as HDDs generally use the SATA or serial-attached SCSI (SAS) interface to transfer data to and from the host computing system.