Hardware Basics:

Inside the Box

2

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Chapter Outline

“There is no invention – only discovery.”

Thomas J. Watson, Sr.

What Computers Do

A Bit About Bits

The Computer’s Core: CPU and Memory

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What Computers Do

Receive input Process Information

Produce Output

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What Computer Do

Store Information

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Input Devices

• Computers accept information from the outside world

• The keyboard is the most common input device

• Pointing devices like the mouse also receive input

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Output Devices

• Computers produce information and send it to the outside world.

• A video monitor is a common output device.

• Printers also produce output.

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Process Information

• The processor, or central processing unit (CPU), processes information and performs all the necessary arithmetic calculations.

The CPU is like the “brain” of the computer.

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Store Information

• Memory and storage devices are used to store information

Primary storage is the computer’s main memory

Secondary storage uses disks or other media

Input

devices

Output devices

Processors

Storage

Hardware

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Information

Information comes in many forms

Words . . . Numbers . . . Pictures . . . Sounds

Computers only understand information in digital form Information must be

broken into bits

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A Bit About Bits

• A bit (binary digit)– is the smallest unit of

information

– can have two values

– can represent numbers, codes, or instructions

Think of these values as switches: yes and no, black and white, high and low, or onand off

“Even the most sophisticated ocmputer is really only a large well-organized volume of bits.”

David Harel

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More about Bits

• Each switch can be used to store a tiny amount of information, such as:

– An answer to a yes/no question

– A signal to turn on a light

• Larger chunks of information are stored by grouping bits as units

– 8 bits (byte) = 256 different messages

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Bits as Codes

• ASCII - American Standard Code for Information Interchange

– most widely used code, represents each character as a unique 8-bit code.

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Bits as Instructions

• The computer stores programs as collections of bits.

– For instance, 01101010 might instruct the computer to add two numbers.

• Other bit instructions might include where to find numbers stored in memory or where to store them.

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Bits, Bytes, and Buzzwords

• Common terms might describe file size or memory size:

– Bit: smallest unit of information

– Byte: a grouping of eight bits of information

– K: (kilobyte); about 1,000 bytes of information - technically 1024 bytes equals 1K of storage.

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Bits, Bytes, and Buzzwords

MB: (megabyte): about 1 million bytes of information

GB: (gigabyte): about 1 billion bytes of information

TB: (terabyte): about 1 million megabytes of information

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The Computer’s Core:The CPU and Memory

• The transformations are performed by the CPU - the central processing unit or processor.

• The microprocessor, which is a silicon chip, is located on the motherboard.

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The CPU:The Real Computer

When purchasing a computer, selecting a CPU is very important. The two most critical factors are compatibility and speed.

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Compatibility

• Not all software is compatible with any given CPU. Each computer has a unique instruction set - a vocabulary of instructions the processor can execute.

• New microprocessors can usually run older software, but new software is not usually compatible with old microprocessors.

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Speed

• The computer’s speed is measured by the speed of its internal clock - a device to synchronize the electric pulses.

Speed is measured in units called megahertz (mHz).

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Speed

• A computer’s speed cannot be judged by megahertz alone.

Speed is also determined by the architecture of the processor – how individual components of the CPU are put together on the chip. Newer chips can manipulate more bits

simultaneously than older chips.

Typically a CPU can process between 16 to 64 bits.

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Speed

Manufacturers have switched from CISC to RISC processors so tasks can be performed faster. CISC - complex instruction set

computer RISC - reduced instruction set

computer

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Speed

• Parallel processing places multiple processors in a computer.

• Most supercomputers have multiple processors that divide jobs into pieces and work in parallel on the pieces.

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The Computer’s Memory

RAM (random access memory):– is the most common type of primary

storage, or computer memory

– is used to store program instructions and data temporarily

– unique addresses and can be stored in any location

– can quickly retrieve information

– will not remain if power goes off (volatile)

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The Computer’s Memory

• ROM (read-only memory):

– information is stored permanently on a chip.

– contains startup instructions and other permanent data.

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Buses, Ports, and Peripherals

• Information travels between components through groups of wires called buses.

Buses connect to storage devices in open areas in the box called bays.

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Buses, Ports, and Peripherals

• Busses also connect to slots inside the computer as well assockets on the outside of the computer called ports.

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Buses, Ports, and Peripherals

• Slots and ports also allow external devices called peripherals to be added to the system (keyboard, monitor, and mouse).

Without peripherals, the CPU and memory are like a brain without a body.