INSIDE THE COMPUTER:

CENTRAL PROCESSING UNIT (CPU)

AND INPUT/OUTPUT DEVICES

EXPANSION BOARDS : adding capabilities

Graphics adapter – permit interfacing with video monitors (VGA video graphics array and AGP

accelerated graphics port enable interfacing of high-resolution monitors with the processor)

Sound card – enables sound to be captured and stored on disk; and enables sound to be played through external speakers

Data/voice/fax modem – permits communication with remote computers via a telephone-line link. On top of the functions of a regular modem, this one also enables you to make phone calls, and allows your PC to mimic a fax machine.

Databuses

IDE cable

A fleet of buses

ISA bus – the oldest and the slowestis being phased out of modern PCs

PCI local bus – enables expansion boards to be linked directly to the system’s common bus

SCSI bus – alternative to the expansion busup to 15 devices can be linked along a single cable (daisy chained),internal and external, with multiple SCSI connectors

USB (universal serial bus) – permits up to 127 peripheral devices to be connected to a single USB port. Eliminates the hassle of installing expansion cards.

The Motherboard

Serial versus Parallel Ports

Serial port – allows the serial transmission of data, one bit at a timeeg. An external modem

Parallel port – allows the parallel transmission of dataie several bits simultaneouslyeg printers, external magnetic disk units, and other computers

SCSI port – provides parallel interface to the SCSI bus that enables faster data transmission than serial and parallel ports

Intel 80826 microprocessor

A memory containing both data and instructions. Also to allow both data and instruction memory locations to be read from, and written to, in any desired order.

A calculating unit capable of performing both arithmetic and logical operations on the data.

A control unit, which could interpret an instruction retrieved from the memory and select alternative courses of action based on the results of previous operations.

von Neumann Architecture :

The microprocessor does the following:

1- Carries out commands to make the hardware components perform actions. 2- Processes data. This involves:

- Performing logical instructions such as comparing - Performing mathematical instructions such as adding and subtracting

The microprocessor can be referred to as the brain of the PC. The microprocessor is also known as the CPU (Central

Processing Unit).

CPU

The CPU is the computer’s brain. This device does all of the processing within the computer.

CPU stands for Central Processing Unit.

CPU speeds are calculated in terms of megahertz, this is known as the system clock speed.

 What is a hertz?

A hertz is a unit of measurement based on one second. It is what is known as a frequency measurement. A frequency is something

that cycles from one point to another point.

MegahertzThe term mega can be considered approximately 1 million. So

therefore a megahertz will be approximately 1 million cycles within one second.

 The term megahertz is to identify CPU clock speed. It will

determine how fast that computer can process data.

For example a computer, which has a clock speed of 500MHz, can process 500 million bits of data within one

second.

MIPS (Millions of Instructions Per Second)

This measures the number of instructions a microprocessor is capable of performing in a second. Once again, the higher the number, the faster the processor.

The table below shows the main types of Intel microprocessor (up to the Pentium MMX) with their speeds measured in MIPS:

                                                      

While clock speed is the most commonly used indicator of performance, it does not always provide an accurate guide. For example, a 486 processor with an internal clock speed of 100Mhz will be slower than Pentium 90Mhz or even 75Mhz, due to their different internal architecture.

INPUT: Keyboard

OUTPUT: Printers

LASER

INK-JET

LASER PRINTERS

INK-JET PRINTERS

Prior to printing, an electrostatic charge is applied to a drum. Then laser beam paths to the drum are altered by a spinning multisided mirror.The reflected beams selectively remove the electrostatic charge from the drum.Toner is deposited on these portions of the drum.The drum is rotated and the toner is fused to the paper to create image.

Tiny droplets of ink, in either blue, red, yellow or black, are positioned with great precision on the paper to form characters and images.

Movement of the print heads and paper are coordinated under program control.