Inside the Ultimate Machine

Monika Gope

LecturerIICT

Inside The Computer

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ROM(Read Only Memory)

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ROM• Permanently stores data; non-volatile, never loses its

content.

• ROM holds the instructions that the computer needs to operate.

•  Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty

• Every  computer needs some form of non-volatile storage to store the initial program that runs when the computer is powered on or otherwise begins execution (a process known as bootstrapping, often abbreviated to "booting" or "booting up").

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Types of ROM

• PROM (Programmable Read Only Memory) memories were developed at the end of the 70s by a company called Texas Instruments. These memories are chips comprising thousands of fuses (or diodes) that can be "burnt" using a device called a " ROM programmer", applying high voltage (12V) to the memory boxes to be marked. The fuses thus burnt correspond to 0 and the others to 1. 

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Types of ROM• EPROM (Erasable Programmable Read Only Memory)

memories are PROMs that can be deleted. These chips have a glass panel that lets ultra-violet rays through. When the chip is subjected to ultra-violet rays with a certain wavelength, the fuses are reconstituted, meaning that all the memory bits return to 1. This is why this type of PROM is called erasable. 

• EEPROM (Electrically Erasable Read Only Memory memories are also erasable PROMs, but unlike EPROMs, they can be erased by a simple electric current, meaning that they can be erased even when they are in position in the computer. 

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Processor

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Processor • Computer uses two components : Memory,

Processor .

• Processor is like the brain of the computer. Processor’s power- How many Transistors it has.

• Processor usually consists of one or more special chips called microprocessor.

• Microprocessor is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and provides results as output.

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Processor

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Processor

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• Mother board is the master circuit board.

• Term CPU (Central Processing Unit) refers Processor .

Processor

Performances of a Processor depends:

• Number of registers• Word size• Bus speed• Cache size

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How to process Processor

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How Computers Represent Data• Computer processing is performed by transistors,

which are switches with only two possible states: on and off.

• All computer data is converted to a series of binary numbers– 1 and 0. For example, you see a sentence as a collection of letters, but the computer sees each letter as a collection of 1s and 0s.

• If a transistor is assigned a value of 1, it is on. If it has a value of 0, it is off. A computer's transistors can be switched on and off millions of times each second.

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How Computers Represent Data

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How Computers Represent Data

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To convert data into strings ofnumbers, computers use the binary number system.

Humans use the decimal system (“deci” stands for “ten”).

The binary number system works thesame way as the decimal system, buthas only two available symbols (0 and1) rather than ten (0, 1, 2, 3, 4, 5, 6, 7,8, and 9).

How Computers Represent Data• A single unit of data is called a bit, having a value of

1 or 0.

• Computers work with collections of bits, grouping them to represent larger pieces of data, such as letters of the alphabet.

• Eight bits make up one byte. A byte is the amount of memory needed to store one alphanumeric character.

• With one byte, the computer can represent one of 256

• different symbols or characters.

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How Computers Represent Data

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How Computers Represent Data• A text code is a system that uses binary numbers (1s

and 0s) to represent characters understood by humans (letters and numerals).

• An early text code system, called EBCDIC uses eight bit codes, but is used primarily in older mainframe systems.

• In the most common text-code set, ASCII, each character consists of eight bits (one byte) of data. ASCII is used in nearly all personal computers.

• In the Unicode text-code set, each character consists of 16 bits (two bytes) of data.

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How Computers Represent Data• EBCDIC-Extended Binary Coded Decimal

Interchange Code 8 bits, 0-256 Character • ASCII-American Standard Code for

Information Interchange 8 bits, 0-127 Character• Extended ASCII 8 bits, 128-256 Character• Unicode- Unicode World Wide Character

Standard 32 bits, 4 Billion Character

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Example of ASCII Text Code

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How Computers Process Data

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How Computers Process Data

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The Arithmetic Logic Unit• The actual manipulation of data takes place in the

ALU.

• The ALU can perform arithmetic and logic operations.

• The ALU is connected to a set of registers—small memory areas in the CPU, which hold data and program instructions while they are being processed.

• Everything has to be broken down into these few operations.

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ALU Operations List

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Bus• A bus is a path between the components of a

computer. Data and instructions travel along these paths.

• The data bus' width determines how many bits can be transmitted between the CPU and other devices.

• The address bus runs only between the CPU and RAM, and carries nothing but memory addresses for the CPU to use.

• Peripheral devices are connected to the CPU by an expansion bus.

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Bus

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Cache Memory

• Cache memory is high-speed memory that holds the most recent data and instructions that have been loaded by the CPU.

• Cache is located directly on the CPU or between the CPU and RAM, making it faster than normal RAM.

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Cache Memory

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Storage device• Computer needs a place to keep the data and

program files when they are not in use.

• The hardware that writes data to or reads data from a

storage medium is called a storage device.

• RAM is like a work table and storage is like a file cabinet.

• Users often confuse storage with memory.

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Storage device

Distinction between storage and memory:

• There is more room in storage than there is in memory.

• Contents are retained in storage when the computer is turned off, whereas the programs or data you put into memory disappear when you shut down the computer.

• Storage is much slower compared to memory, but also much cheaper than memory.

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Storage device

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The two primary storage technologies are magnetic and optical.

The primary types of magnetic storage are:

• Diskettes (floppy disks)• Hard disks• High-capacity floppy disks• Disk cartridges• Magnetic tape

Storage device

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The two primary storage technologies are magnetic and optical.

The primary types of optical storage are:

• Compact Disk Read-Only Memory (CD-ROM)• Digital Video Disk Read-Only Memory (DVD-

ROM)• CD-Recordable (CD-R)• CD-Rewritable (CD-RW)• PhotoCD

Magnetic Storage Device

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-How Magnetic Storage Works

• A magnetic disk's medium contains iron particles, which can be polarized—given a magnetic charge—in one of two directions.

• Each particle's direction represents a 1 (on) or 0 (off), representing each bit of data that the CPU can recognize.

• A disk drive uses read/write heads containing electromagnets to create magnetic charges on the medium.

Magnetic Storage Devices – Formatting• Before a magnetic disk can be used, it must be

formatted—a process that maps the disk's surface and determines how data will be stored.

• During formatting, the drive creates circular tracks around the disk's surface, then divides each track into sectors.

• The OS organizes sectors into groups, called clusters, then tracks each file's location according to the clusters it occupies.

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Magnetic Storage Devices – Formatting

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Magnetic Storage Devices - How OS finds Data When a disk is formatted, the OS creates four areas on

its surface:• Boot sector – stores the master boot record, a small

program that runs when you first start (boot) the computer

• File allocation table (FAT) – a log that records each file's location and each sector's status

• Root folder – enables the user to store data on the disk in a logical way

• Data area – the portion of the disk that actually holds data

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How OS finds Data

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Magnetic Storage Devices - Hard Disks• Hard disks use multiple platters, stacked on a

spindle. Each platter has two read/write heads, one for each side.

• Hard disks use higher-quality media and a faster rotational speed than diskettes.

• Removable hard disks combine high capacity with the convenience of diskettes.

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Hard Disks

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Hard Disks

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Optical Storage Devices –How Optical Storage Works• An optical disk is a high-capacity storage

medium. An optical drive uses reflected light to read data.

• To store data, the disk's metal surface is covered with tiny dents (pits) and flat spots (lands), which cause light to be reflected differently.

• When an optical drive shines light into a pit, the light cannot be reflected back. This represents a bit value of 0 (off). A land reflects light back to its source, representing a bit value of 1 (on).

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How Optical Storage Works

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Optical Storage Devices –CD-ROM

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• In PCs, the most commonly used optical storage technology is called Compact Disk Read-Only Memory (CD-ROM).

• A standard CD-ROM disk can store up to 650 MB of data, or about 70 minutes of audio.

• Once data is written to a standard CD-ROM disk, the data cannot be altered or overwritten.

Optical Storage Devices –DVD-ROM

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• A variation of CD-ROM is called Digital Video Disk Read-Only Memory (DVD-ROM), and is being used in place of CD-ROM in many newer PCs.

• Standard DVD disks store up to 9.4 GB of data—enough to store an entire movie. Dual-layer DVD disks can store up to 17 GB.

• DVD disks can store so much data because both sides of the disk are used, along with sophisticated data compression technologies.

Ports

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Ports

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Education is what remains after one has

forgotten everything he learned in school.

Einstein