Hardware Basics: Inside the Box  

After reading completing this unit, you should be able to:

• Explain in general terms how computers store and manipulate information
• Describe the basic structure and organization of a computer
• Discuss the functions and interactions of a computer system's principal internal components
• Explain why a computer typically has different types of memory and storage devices
• Describe several examples of input and output devices and explain how they enhance a computer's usefulness

In this learning unit you will examine computer hardware. After an overview of the organization of a computer system, we will concentrate on the CPU, memory, and peripherals.

What Computers Do:

Computers can really do only four things:

• Receive input.
• Process information.
• Produce output.
• Store information.

 

The four basic hardware components of every computer system are:

1. Input devices (peripherals) accept input from the outside world. The most common input device is the keyboard. Other input devices include pointing devices like mice and joysticks, scanners and digital cameras. Click here for a closer look at peripherals

2. Output devices, also called peripherals, send information to the outside world. Most computers use a TV-like video monitor as their main output device and some kind of printer for producing paper printouts.

3. A processor, or central processing unit (CPU), processes information, performing all the necessary arithmetic calculations and making basic decisions based on information values.

4. Storage devices and memory are used to store information. The most common storage devices are disk drives and tape drives. Different types of memory are used for different long-term and short-term storage tasks.

A Bit About Bits

The term information is difficult to define because it has many meanings. In this course we will apply the term information to just about anything that can be communicated, whether it has value or not. In the world of computers, information is digital: It’s made up of discrete units, that is, units that can be counted, so it can be subdivided. Computers can only digest information that has been broken into bits. A bit (binary digit) is the smallest unit of information. A bit can have one of two values: on or off. A computer can process larger chunks of information by treating groups of 8 bits as units, usually called a byte, which can represent 256 different messages (256 = 28).

Building with Bits

A string of bits can be interpreted as a number, a letter of the alphabet, or almost anything else.

Bits as numbers:

Computers represent numbers using the binary number system; a system that denotes all numbers with combinations of two digits. In the binary number system, every number is represented by a unique string of Os and is.

Bits as codes.

To make words, sentences, and paragraphs fit into the computer’s binary-only circuitry, people have devised codes that represent each letter, digit, and special character as a unique string of bits. The most widely used code, ASCII (an abbreviation of American Standard Code for Information Interchange, but generally pronounced "as-kee"), represents each character as a unique 8-bit code. There are 256 unique codes for each of the letters (uppercase and lowercase), numbers, and special characters that we commonly use in written English communication. To facilitate multilingual computing, manufacturers are likely to switch eventually from ASCII to a more information-rich coding scheme, such as UniCode’s 65,000-character set

Bits as instructions in programs.

Programs, like characters, are represented in binary notation through the use of codes.

Bits, Bytes, and Buzzwords

•Byte: a grouping of 8 bits.

• KB (kilobyte, sometimes called K): about 1000 bytes of information.

 

• MB (megabyte, sometimes called meg): approximately 1000 K, or 1 million bytes.

 

• GB (gigabyte, sometimes called gig): approximately 1000 megabytes.

 

• TB (terabyte): approximately 1 million megabytes.

A file is an organized collection of information, such as a term paper or a set of names and addresses, stored in a computer-readable form.

The CPU: The Real Computer

The transformations are performed by the central processing unit (CPU) or processor. A modern CPU is an extraordinarily complex collection of electronic circuits. When all of those circuits are built into a single silicon chip, as they are in most computers today, that chip is referred to as a microprocessor. In a typical desktop computer, the CPU is housed along with other chips and electronic components on a circuit board.

 

Compatibility:

Not all software is compatible with every CPU; that is, software written for one processor probably won’t work with another.

Speed:

A computer’s speed is determined in part by the speed of its internal clock; the timing device that produces electrical pulses to synchronize the computer’s operations. Computers are often described in terms of their clock speeds, measured in units called megahertz. Speed is also determined by the architecture of the processor; the design that determines how individual components of the CPU are put together on the chip. Parallel processing puts more than one processor in a computer.

Primary Storage: The Computer’s Memory

RAM (random access memory) is the most common type of primary storage, or computer memory. RAM chips contain circuits that can be used to store program instructions and data temporarily. You can store a piece of information in any RAM location&endash;you can pick one at random&endash;and the computer can, if so instructed, quickly retrieve it. RAM is called volatile memory because information stored there is not held permanently.

The computer also has nonvolatile memory called ROM (read-only memory) because the computer can only read information from it; it can never write any new information on it. ROM isn’t always hidden away on chips inside the computer’s chassis. Many home video game machines and home computers use removable ROM cartridges as permanent storage devices for games and other programs.

 

Buses, Ports, and Peripherals:

Information travels between a computer’s components through groups of wires called buses. Buses typically have 8, 16, or 32 wires; a bus with 16 wires is called a 16-bit bus because it can transmit 16 bits of information at once&endash;twice as many as an 8-bit bus. Some buses connect to slots inside the computer’s housing. Users can customize their computers by inserting special-purpose circuit boards (usually called cards or just boards) into these slots. Other buses connect to external ports&endash;sockets on the outside of the computer chassis. Slots and ports make it easy to add external devices, or peripherals, to the computer system so the CPU can communicate with the outside world and store information for later use.

architecture, ASCII, binary, bit, bus, byte, central processing unit (CPU), circuit board, compatible

digital, file, (GB) gigabyte, information, input device, (KB) kilobyte, (MB) megabyte, memory

nonvolatile memory, parallel processing, PC card, peripheral , processor,

RAM (random access memory), RISC (reduced instruction set computer),

ROM (read-only memory), storage device, (TB) terabyte, UniCode, volatile memory

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