An electronic calculator is a small, portable electronic device used to perform both arithmetic operations and complex mathematical operations.

The first solid electronic calculator was created in the 1960 s, building on the extensive history of tools such as the abacus (developed around 2000 BC), and the mechanical calculator (developed in the 17^th century AD). It was developed in parallel with the analog computers of the day.

In addition to general purpose of 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 higher dimensional Euclidean space.

It was developed in parallel with the analog computers of the day. The underlined word refers to ...

A laptop is a kind of computer unit which has the same function as a PC (Personal Computer), but it’s smaller, lighter and of different sizes. Nowadays, most people choose laptops for several reasons.

A laptop is a portable device. This portability is very helpful for our work, study and other activities. We do not need complicated cable installations to activate a laptop. With a laptop, we can do our work anytime and anywhere.

Moreover, a laptop allows us to access the internet in public places which provide free access called hot spot areas. Some people like to use this facility to carry out their tasks.

Finally, a laptop consumes energy more efficiently than a PC does. This device uses a rechargeable battery as a source of electric energy. So, if we prefer using a laptop, it means that we support the government program to save energy. That’s why a laptop has become very popular recently.

What is the purpose of the text above?

A laptop is a kind of computer unit which has the same function as a PC (Personal Computer), but it’s smaller, lighter and of different sizes. Nowadays, most people choose laptops for several reasons.

A laptop is a portable device. This portability is very helpful for our work, study and other activities. We do not need complicated cable installations to activate a laptop. With a laptop, we can do our work anytime and anywhere.

Moreover, a laptop allows us to access the internet in public places which provide free access called hot spot areas. Some people like to use this facility to carry out their tasks.

Finally, a laptop consumes energy more efficiently than a PC does. This device uses a rechargeable battery as a source of electric energy. So, if we prefer using a laptop, it means that we support the government program to save energy. That’s why a laptop has become very popular recently.

A public place where we can have free access to the internet is …

A laptop is a kind of computer unit which has the same function as a PC (Personal Computer), but it’s smaller, lighter and of different sizes. Nowadays, most people choose laptops for several reasons.

A laptop is a portable device. This portability is very helpful for our work, study and other activities. We do not need complicated cable installations to activate a laptop. With a laptop, we can do our work anytime and anywhere.

Moreover, a laptop allows us to access the internet in public places which provide free access called hot spot areas. Some people like to use this facility to carry out their tasks.

Finally, a laptop consumes energy more efficiently than a PC does. This device uses a rechargeable battery as a source of electric energy. So, if we prefer using a laptop, it means that we support the government program to save energy. That’s why a laptop has become very popular recently.

A laptop has become very popular because …

A laptop is a kind of computer unit which has the same function as a PC (Personal Computer), but it’s smaller, lighter and of different sizes. Nowadays, most people choose laptops for several reasons.

A laptop is a portable device. This portability is very helpful for our work, study and other activities. We do not need complicated cable installations to activate a laptop. With a laptop, we can do our work anytime and anywhere.

Moreover, a laptop allows us to access the internet in public places which provide free access called hot spot areas. Some people like to use this facility to carry out their tasks.

Finally, a laptop consumes energy more efficiently than a PC does. This device uses a rechargeable battery as a source of electric energy. So, if we prefer using a laptop, it means that we support the government program to save energy. That’s why a laptop has become very popular recently.

“ …a laptop allows us….” (paragraph 1 line 1)

The underlined word has the opposite meaning with …

A laptop is a kind of computer unit which has the same function as a PC (Personal Computer), but it’s smaller, lighter and of different sizes. Nowadays, most people choose laptops for several reasons.

A laptop is a portable device. This portability is very helpful for our work, study and other activities. We do not need complicated cable installations to activate a laptop. With a laptop, we can do our work anytime and anywhere.

Moreover, a laptop allows us to access the internet in public places which provide free access called hot spot areas. Some people like to use this facility to carry out their tasks.

Finally, a laptop consumes energy more efficiently than a PC does. This device uses a rechargeable battery as a source of electric energy. So, if we prefer using a laptop, it means that we support the government program to save energy. That’s why a laptop has become very popular recently.

From the text we know that ….

A camera is an optical instrument for recording images, which may be stored locally, transmitted to another location, or both. The images may be individual still photographs or sequences of images constituting videos or movies. The functioning of the camera is very similar to the functioning of the human eye.

A camera may work with the light of the visible spectrum or with other portions of the electromagnetic spectrum. A still camera is an optical device which creates a single image of an object or scene, and records it on an electronic sensor or photographic film. All cameras use the same basic design: light enters an enclosed box through a converging lens and an image is recorded on a light-sensitive medium.

A shutter mechanism controls the length of time that light can enter the camera. Most photographic cameras have functions that allow a person to view the scene to be recorded, allow for a desired part of the scene to be in focus, and to control the exposure so that it is not too bright or too dim.

A movie camera or a video camera operates similarly to a still camera, except it records a series of static images in rapid succession, commonly at a rate of 24 frames per second. When the images are combined and displayed in order, the illusion of motion is achieved.

What kind of text is it?

A camera is an optical instrument for recording images, which may be stored locally, transmitted to another location, or both. The images may be individual still photographs or sequences of images constituting videos or movies. The functioning of the camera is very similar to the functioning of the human eye.

A camera may work with the light of the visible spectrum or with other portions of the electromagnetic spectrum. A still camera is an optical device which creates a single image of an object or scene, and records it on an electronic sensor or photographic film. All cameras use the same basic design: light enters an enclosed box through a converging lens and an image is recorded on a light-sensitive medium.

A shutter mechanism controls the length of time that light can enter the camera. Most photographic cameras have functions that allow a person to view the scene to be recorded, allow for a desired part of the scene to be in focus, and to control the exposure so that it is not too bright or too dim.

A movie camera or a video camera operates similarly to a still camera, except it records a series of static images in rapid succession, commonly at a rate of 24 frames per second. When the images are combined and displayed in order, the illusion of motion is achieved.

What is the purpose of this text?

A camera is an optical instrument for recording images, which may be stored locally, transmitted to another location, or both. The images may be individual still photographs or sequences of images constituting videos or movies. The functioning of the camera is very similar to the functioning of the human eye.

A camera may work with the light of the visible spectrum or with other portions of the electromagnetic spectrum. A still camera is an optical device which creates a single image of an object or scene, and records it on an electronic sensor or photographic film. All cameras use the same basic design: light enters an enclosed box through a converging lens and an image is recorded on a light-sensitive medium.

A shutter mechanism controls the length of time that light can enter the camera. Most photographic cameras have functions that allow a person to view the scene to be recorded, allow for a desired part of the scene to be in focus, and to control the exposure so that it is not too bright or too dim.

A movie camera or a video camera operates similarly to a still camera, except it records a series of static images in rapid succession, commonly at a rate of 24 frames per second. When the images are combined and displayed in order, the illusion of motion is achieved.

The function of camera is described in paragraph …

A camera is an optical instrument for recording images, which may be stored locally, transmitted to another location, or both. The images may be individual still photographs or sequences of images constituting videos or movies. The functioning of the camera is very similar to the functioning of the human eye.

A camera may work with the light of the visible spectrum or with other portions of the electromagnetic spectrum. A still camera is an optical device which creates a single image of an object or scene, and records it on an electronic sensor or photographic film. All cameras use the same basic design: light enters an enclosed box through a converging lens and an image is recorded on a light-sensitive medium.

A shutter mechanism controls the length of time that light can enter the camera. Most photographic cameras have functions that allow a person to view the scene to be recorded, allow for a desired part of the scene to be in focus, and to control the exposure so that it is not too bright or too dim.

A movie camera or a video camera operates similarly to a still camera, except it records a series of static images in rapid succession, commonly at a rate of 24 frames per second. When the images are combined and displayed in order, the illusion of motion is achieved.

From the text, we know that …

A camera is an optical instrument for recording images, which may be stored locally, transmitted to another location, or both. The images may be individual still photographs or sequences of images constituting videos or movies. The functioning of the camera is very similar to the functioning of the human eye.

A camera may work with the light of the visible spectrum or with other portions of the electromagnetic spectrum. A still camera is an optical device which creates a single image of an object or scene, and records it on an electronic sensor or photographic film. All cameras use the same basic design: light enters an enclosed box through a converging lens and an image is recorded on a light-sensitive medium.

A shutter mechanism controls the length of time that light can enter the camera. Most photographic cameras have functions that allow a person to view the scene to be recorded, allow for a desired part of the scene to be in focus, and to control the exposure so that it is not too bright or too dim.

A movie camera or a video camera operates similarly to a still camera, except it records a series of static images in rapid succession, commonly at a rate of 24 frames per second. When the images are combined and displayed in order, the illusion of motion is achieved.

The word rapid in par.4 has similar meaning like…