Main Difference
The main difference between Computer and Calculator is that the Computer is a simple generalpurpose device for performing arithmetic or logical operations and Calculator is a electronic device used to perform operations of arithmetic.

Computer
A computer is a device that can be instructed to carry out sequences of arithmetic or logical operations automatically via computer programming. Modern computers have the ability to follow generalized sets of operations, called programs. These programs enable computers to perform an extremely wide range of tasks.
Computers are used as control systems for a wide variety of industrial and consumer devices. This includes simple special purpose devices like microwave ovens and remote controls, factory devices such as industrial robots and computeraided design, and also general purpose devices like personal computers and mobile devices such as smartphones.
Early computers were only conceived as calculating devices. Since ancient times, simple manual devices like the abacus aided people in doing calculations. Early in the Industrial Revolution, some mechanical devices were built to automate long tedious tasks, such as guiding patterns for looms. More sophisticated electrical machines did specialized analog calculations in the early 20th century. The first digital electronic calculating machines were developed during World War II. The speed, power, and versatility of computers have been increasing dramatically ever since then.
Conventionally, a modern computer consists of at least one processing element, typically a central processing unit (CPU), and some form of memory. The processing element carries out arithmetic and logical operations, and a sequencing and control unit can change the order of operations in response to stored information. Peripheral devices include input devices (keyboards, mice, joystick, etc.), output devices (monitor screens, printers, etc.), and input/output devices that perform both functions (e.g., the 2000sera touchscreen). Peripheral devices allow information to be retrieved from an external source and they enable the result of operations to be saved and retrieved.

Calculator
An electronic calculator is typically a portable electronic device used to perform calculations, ranging from basic arithmetic to complex mathematics.
The first solidstate electronic calculator was created in the early 1960s. Pocketsized devices became available in the 1970s, especially after the Intel 4004, the first microprocessor, was developed by Intel for the Japanese calculator company Busicom. They later became used commonly within the petroleum industry (oil and gas).
Modern electronic calculators vary from cheap, giveaway, creditcardsized models to sturdy desktop models with builtin printers. They became popular in the mid1970s as the incorporation of integrated circuits reduced their size and cost. By the end of that decade, prices had dropped to the point where a basic calculator was affordable to most and they became common in schools.
Computer operating systems as far back as early Unix have included interactive calculator programs such as dc and hoc, and calculator functions are included in almost all personal digital assistant (PDA) type devices, the exceptions being a few dedicated address book and dictionary devices.
In addition to general purpose calculators, there are those designed for specific markets. For example, there are scientific calculators which include trigonometric and statistical calculations. Some calculators even have the ability to do computer algebra. Graphing calculators can be used to graph functions defined on the real line, or higherdimensional Euclidean space. As of 2016, basic calculators cost little, but scientific and graphing models tend to cost more.
In 1986, calculators still represented an estimated 41% of the world’s generalpurpose hardware capacity to compute information. By 2007, this had diminished to less than 0.05%.

Computer (noun)
A person employed to perform computations; one who computes. from 17th c.

Computer (noun)
A male computer, where the female computer is called a computress.

Computer (noun)
A programmable electronic device that performs mathematical calculations and logical operations, especially one that can process, store and retrieve large amounts of data very quickly; now especially, a small one for personal or home use employed for manipulating text or graphics, accessing the Internet, or playing games or media. from 20th c.
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Calculator (noun)
A mechanical or electronic device that performs mathematical calculations.

Calculator (noun)
A person who performs mathematical calculation

Calculator (noun)
A person who calculates (in the sense of scheming).

Calculator (noun)
A set of mathematical tables.