زبان تخصصی کامپیوتر درس دوم What is a computer

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 Unit 2 : What is a computer

Topic : The components of a computer system

Leaing Objectives:

To understand the basic structure of a computer system

To recognize differences between types of computers

To understand the value of different units of memory

Language Focus : Function of an item

Abbreviations and Acronyms : ASCII, CPU, GB, GHz, IBM, KB, MB, MHz

Key Words : bit (binary digit), byte, circuit, clock speed, configuration, desktop, device, diskette, handheld, input, keyboard, laptop, mainframe, memory, minicomputer, monitor, mouse, multitasking, output, palmtop, peripherals, port, portable, printer, pulse

Reading Comprehension

Reading 1

What would you say if you were asked “What is a computer?” Discuss it with other students. Then read the text and compare your answer.

What is a computer?

Computers are electronic machines which can accept data in a certain form, process the data, and give the results of the processing in a specified format as information. Three basic steps are involved in the process. First, data is fed into the computer’s memory. Then, when the program is run, the computer performs a set of instructions and processes the data. Finally, we can see the results (the output) on the screen or in printed form

A set of instructions that directs the computer to perform some functions is known as software, and the electronic and electromechanical parts that make up a computer system are called hardware. A standard computer system consists of three main hardware sections: the central processing unit (CPU), the main memory, and the peripherals.

Storage devices (floppy, hard, or optical disks) provide a permanent storage of both data and programs. Disk drives are used to handle floppy, hard, or optical disks. Input devices enable data to go into the s memory. The most common input devices are the mouse and the keyboard. Output devices enable us to extract the finished product from the system. For example, the computer shows the output on the monitor or prints the results onto paper by means of a printer.

On the rear panel of the computer, there are several ports into which we can plug a wide range of peripherals – exteal modems, printers, optical drives, and scanners. These are the main physical units of a computer system. The way the physical units of a computer system are put together is generally known as the configuration.

Reading 2

How many types of computer systems do you know? Read the following text

Types of Computer Systems

Computers can be divided into four main types depending on their size and power. They are supercomputers, mainframes, minicomputers, and microcomputers.

Supercomputers are the largest and most powerful computers. They are capable of processing huge amounts of data in a short time. Supercomputers are very expensive and are used for scientific and engineering applications that must handle very large databases or do a great amount of computations such as animated graphics, petroleum exploration, and nuclear energy research.

Mainframes are also large and powerful, but not as large and powerful as supercomputers. The basic configuration of a mainframe consists of a central system which processes large amounts of data very quickly. This central system provides data and computing facilities for hundreds of terminals connected together in a network. Mainframes are usually used by large companies, factories, and universities.

Minicomputers are smaller and less powerful than mainframes. They can handle multitasking, that is, they can perform more than one task at the same time. Minicomputers are mainly used as file servers for terminals. Typical applications include academic computing, software engineering, and other sophisticated applications in which many users share resources.

Microcomputers carry out their processing on a single microchip. They are used as personal computers at home or as workstations for a group. Typical examples are the IBM PC or the Apple Macintosh.

Broadly speaking, there are two classes of microcomputers:

(a) desktop PCs, which are designed to be placed on your desk, and (b) portable PCs, which can be carried. Some portable PCs are as small as a notebook (this is why they are called notebooks or laptops); some are even smaller and can be held in one hand (this is why they are called handheld computers or palmtops). Portable PCs are ideal for business people who travel a lot.

Reading 3

Do you know the main components inside a PC system? Read the following text

What’s inside a PC system?

The nerve center of a PC is the central processing unit or CPU. This unit is built into a single microprocessor chip (with one or more cores) which executes program instructions and supervises the computer’s overall operation. One area where microprocessors differ is in the amount of data – the number of bits – that they can work with at a time. There are 16, 32, and 64-bit processors. A 64-bit processor is able to address 4 billion times more information than a 32-bit system.

The programs and data which pass through the central processor must be loaded onto the main memory (also called the inteal memory) in order to be processed. Thus, when the user runs an application, the microprocessor looks for it on secondary storage devices (disks) and transfers a copy of the instructions into the RAM area. RAM (random access memory) is temporary, i.e. its information is lost when the computer is tued off. However, ROM (read only memory) is permanent and contains instructions needed by the processor to load the operating system.

Most of today’s computers have inteal expansion slots that allow users to install adaptors or expansion boards. Popular adaptors include high-resolution graphics boards, memory expansion boards, and inteal modems.

The power and performance of a computer is partly determined by the speed of its microprocessor. A clock provides pulses at fixed intervals to measure and synchronize circuits and units. The clock speed is measured in MHz (megahertz) or GHz (gigahertz) and refers to the frequency at which pulses are emitted. For example, a CPU running at 3,200 MHz (3,200 million cycles per second) will enable the computer to handle complex applications

Reading 4

What do you know about different units of memory? Are you familiar with bits, bytes, KB, MB, and GB?

Units of Memory

Bits – basic units of memory

Information is processed and stored in computers as electrical signals. A computer contains thousands of electronic circuits connected by switches that can only be in one of two possible states: ON (the current is flowing through the wire) or OFF (the current is not flowing through the wire). To represent these two conditions, we use binary notation in which 1 means ON and 0 means OFF. This is the only way a computer can “understand” anything. Everything about computers is based on this binary process. Each 1 or 0 is called a binary digit or bit (binary + digit → bit).

Bytes and Characters

1s and 0s are grouped into eight-digit codes that represent characters (letters, numbers, and symbols). Eight bits together are called a byte. Thus, each character in a keyboard has its own arrangement of eight bits. For example, 01000001 for the letter A, 01000010 for B, and 01000011 for C.

The ASCII Code

Most computers use a standard system for the binary representation of characters. This is the American Standard Code for Information Interchange, known as ASCII. There are 256 different ways of combining 0 and 1 bits in a byte. So they can give us 256 different signals. However, the ASCII code only uses 128 codes to represent characters. The rest of the codes are used for other purposes. What makes this system powerful is that these codes are standard.

Kilobytes, Megabytes, and Gigabytes

In order to avoid astronomical figures and sums in the calculation of bytes, we use units such as kilobytes, megabytes, and gigabytes. One kilobyte is 1,024 bytes and it is represented as KB, or more informally as K. One megabyte is equivalent to 1,024 KB, and one gigabyte is 1,024 MB. We use these units (KB, MB, GB) to describe the RAM memory, the storage capacity of disks, and the size of any document.