The evolution of computer systems

The evolution of computer systems can be divided into five stages:

• First-generation systems. The first electronic computer, ENIAC, was born in 1946. The first computer designed for sale to business enterprises and other organizations. YUNIVAK (UNIVAC), was created in the early 50s and was used to summarize the results of the US Census. These computers are the first generation to work in the vacuum tube, the earliest electronic elements, which, unfortunately, are often burned out, isolated lot of heat and consume a lot of energy. They used sophisticated programming techniques

• Second generation systems. In the 50s there were transistors, which have been used in the new generation of computers, which have become cheaper, smaller and more reliable than their predecessors. Facilitating their programming, as these new machines use language understandable for ordinary people.

• Third generation systems. By the early 60s computers entered the next stage of development. These computers used integrated circuits, which reduced the size of cars and heat them. Computers purchased this kind of business equipment, and they have started to appear in accounting, warehouses, laboratories and factories around the world.

• Fourth-generation systems. In 1971, computers have become like those machines that we use today. Many of them work on the basis of microprocessors. The development of the fourth generation of systems has led to the birth of personal computers, "Apple I" and "ABM". These are computers that we use today.

• Fifth-generation systems. This class of cars, which embodies the latest achievements of computer technology focus of the development of artificial intelligence and other advanced achievements.

A computer is an electronic machine that makes mathematical calculations and logical comparisons quickly and without any mistakes. Computers take information (called data), process it, and show the results of the processing.

They can store the results forever. For these reasons, computers have become a part of our lives. Computers consist of two parts, hardware and software. Hardware is the physical parts of the computer. Software is the programs in the computer. Software uses hardware to perform operations for the computer user. The relation between hardware and software is like the relation between our body and our spirit.

Computers can store information in two different ways: in permanent storage (for example, on a disk or a CD), and in temporary storage, also called the computer’s memory, or RAM. Data in temporary storage only lasts as long as the computer is switched on. This is why the storage is called temporary. When you switch on a computer, first a special piece of software called the operating system is copied (loaded) from permanent storage to the RAM. The computer gets data from an input device such as a keyboard, mouse, hard disk, or scanner, and makes all the calculations and the comparisons in the central processing unit (CPU). The CPU is like the computer’s brain. It uses the RAM to maintain the data. When the CPU has processed the data, it sends the results to an output device such as a monitor, hard disk, or printer. When you switch a computer off, the computer copies any important data in the RAM back to permanent storage.

The physical parts of a computer are called hardware. In this lecture, we will divide the different types of hardware into four groups: the system unit, input devices, output devices, and storage devices.

The system unit contains the main components of the computer, such as the mainboard, CPU, RAM, video card, hard disk, disk drives, and the power supply. It can also contain optional components such as a sound card or a network card.

We use input devices to give data to the computer. The most common input devices are the keyboard and the mouse. Other types of input device area scanner, joystick, light pen, touch screen, webcam, and digital camera.

Output devices are the components where the computer shows the results. A printer, plotter, and loud speaker are all output devices.

Storage devices are used to store data permanently. A hard disk, floppy disk,CD-ROM, DVD-ROM, Zip disk, and tape cartridge are examples of storage devices.

Some hardware parts (such as the CPU, mainboard, RAM, power supply, keyboard, graphics card, and hard disk) are necessary for computer to work. Some parts are optional and simply increase a computer’s functionality. A printer, a modem, and a network card are examples of optional components.

The System Unit

All of the main components of a computer are grouped together in the system unit. For instance, the system unit includes the computer system’s motherboard (including the processor), and items such as hard disks, floppy disks, and CD-ROM drives, etc.

Chassis

The chassis is the metal and plastic box that contains the system unit. Most people don’t think that the chassis is an important part of the computer. However, it is not just the shell of your computer, it supports all the internal parts. It also protects your system from the outside world and helps to keep the system unit components cool. The closed design and good air flow inside the chassis are especially important for components such as the CPU and hard drive, which can get very hot when they are working.

Mainboard

The mainboard (also called the motherboard, or system board) is the biggest board inside your system unit. All the main components of your computer connect to the mainboard. The CPU is normally situated on your mainboard along with all the other electronic components.

All the other boards (cards) in your computer connect to the mainboard. Other items, such as the hard disk, are attached to the mainboard either directly or via cables. Mainboards are getting smaller and smaller as the components become more integrated. Nowadays, if you open up a system unit it can look quite empty.The ROM-BIOS (Read Only Memory-Basic Input Output System) chip is a special microchip on your computer’s mainboard. It contains software that allows your computer to work with your operating system. For example, itcopies your operating system into RAM when you switch on your computer. Buses are data paths on the motherboard that connect the CPU to the different parts of the mother board, such as the chips and cable connections.

Expansion slots are sockets on the mainboard which allow you to extend the computer’s features and capabilities. Expansion slots hold expansion cards (such as a video card, sound card, or network card) and connect them to the buses. Laptops and other portable computers use special expansion slots called PCMCIA slots, which accept small expansion cards called PC Cards Serial ports are sockets located at the back of your computer that allow you to connect items such as modems to the computer. Serial ports are commonly labeled COM1 or COM2.

Parallel ports are sockets located at the back of your computer that enable you to connect items such as printers to the computer. Parallel ports are commonly labeled LPT1 or LPT2.

PS/2 keyboard and mouse ports are used to connect a keyboard and mouse to the mainboard. A battery on the mainboard is needed to store some important information (such as the date and time, and maybe a user password) while your computer is switched off.

An internal speaker connected to the mainboard allows your computer to send you error or warning beeps while it is running.

The USB (Universal Serial Bus) is quite a new item inside a PC. USB ports are located at the back of the system unit. They allow you to plug in devices designed for the USB such as scanners, digital cameras, and printers. The bus arbitrator (chipset) is an integrated circuit on the motherboard. It controls how the mainboard buses are used. If two different devices try to use the same bus at the same time, there can be a problem. The bus arbitrator prevents this problem.

Central Processing Unit (CPU)

The CPU (Central Processing Unit) is one of the most important components inside your computer. It is like the brain of your computer because it performs all the computer calculations. CPU speed is measured in gigahertz (GHz) and has an important effect on the overall speed of your computer.

Memory (RAM)

RAM (Random Access Memory) is temporary memory that the computer uses to store applications and data that are in use, for example, the operating system, and a word processor or database program. When you create data such as a letter or a picture, the computer stores the data in RAM and then copies it to the hard disk when you save your work.

IDE Interface

Storage devices such as floppy disk drives, hard disk drives, and CD-ROM drives usually connect to the computer through an IDE (Integrated Drive Electronics) interface. An IDE interface is a standard way for storage devices to connect to a computer. IDE is not the original technical name for the interface standard. It was originally called AT Attachment (ATA) technology, because engineers developed it for the IBM AT computer.

PCI Bus

During the early 1990s, Intel introduced a new bus standard, the Peripheral Component Interconnect (PCI). A PCI bus connects the CPU,memory, and expansion slots on the mainboard. PCI is faster and more reliable than older bus technologies such as ISA.

A PCI bus can connect up to five expansion slots (external devices) to the CPU. Usually there is only one PCI bus on a mainboard, although some mainboards have more.

Graphics Card

Modern computers use a lot of graphics. Many operating systems use a graphical user interface (GUI) as the main interface between the user and the computer. You might also enjoy playing video games or creating 3D graphics and animation. In fact, if you use your computer for anything except basic office tasks, you probably use lots of graphics.

A graphics card in a modern PC can connect to the mainboard in one of several different ways: On-board - The graphics chips and memory are part of the mainboard.

PCI - The graphics card plugs into the PCI bus.􀂈 AGP - The graphics card plugs into a special slot designed especially for graphics devices. AGP (Accelerated Graphics Port) is a special bus technology that was developed by Intel as a way to improve the performance and speed of graphics hardware connected to a PC.

SCSI Bus

Most home and small-office PCs use an IDE hard disk drive and have a PCI bus for adding components to the computer. However, a lot of computers, particularly expensive workstations and older Apple Macintosh computers, use a SCSI (Small Computer System Interface) bus to connect components such as hard disk drives, scanners, CD-ROM drives, printers and tape drives to the mainboard.

Video Card (Video Adapter)

A video card converts the digital signals in a computer to a special format that can be displayed on a monitor. Some video cards also have a TV out to use a TV as a screen. A video card has its own microprocessor and memory. Today, the size of the memory is up to 128 megabytes.

Power Supply

The power supply is an electrical device that transforms the standard electricity supply (115-120 Volts AC in the United States, or 220 Volts AC in Europe) into the lower voltages (3.3, or 5 to 12 volts DC) that computer systems require. Personal computer power supplies are measured in watts. They usually range from about 90 watts to 300 watts.

Sound Card

A sound card converts digital sound signals to analog sound signals and sends them to the speakers so that you can hear sounds. If you have a microphone and suitable software, you can also record sounds. You can also buy special software called speech recognition software, which recognizes your voice and displays the words you say on your monitor. In the future, speech recognition software might replace the keyboard.

Network Interface Card (NIC)

A network interface card allows computers to communicate with each other through cables. It converts digital signals to analog signals and sends these analog signals to other network interface cards in other computers.

Those cards convert the analog signals back to digital signals. In this way, computers can communicate with each other. Network interface cards are often used in offices to connect computers in the same room or building. To communicate over longer distances, office computers usually use a modem.

Modem (Modulator/Demodulator)

A modem is a device that connects your computer to the telephone system. A modem converts digital data on your computer into analog signals that can be sent over a telephone line. It also converts the analog signals that it receives into digital data. If you want to connect to the Internet using a telephone line, you will need a modem.

TV Card

TV cards usually have two functions, TV decoding and TV tuning. The TV decoder transfers the picture that is on the screen to a TV. This is sometimes useful for business presentations. The TV tuner allows you to watch TV channels on the monitor so that your monitor becomes like a TV.

PC Card

A PC card is a small, creditcard-sized board that extends a computer’s ability, for example, by providing more memory, or working like a modem. PC cards are particulary useful for laptops and other personal computers which do not have room for full-size expansion cards. PC cards connect to the outside of a computer through a special socket, called a PCMCIA slot.

Input Devices

Keyboard

The keyboard is the most common way to enter information into a computer. Today, standard keyboards have 104 or 105 keys. An electronic circuit inside the keyboard transmits the code of a pressed key to the CPU.

Mouse

A mouse is another very popular input device, which is used to point to things and select things on the screen. A small ball underneath the mouse tells the computer when the mouse is moved across a surface, and the computer moves the on-screen pointer to follow.There are usually two or three mouse buttons that you can press (‘click’) to choose commands and select things on the screen. Two mouse clicks close together are called a ‘double click’

Scanner

A scanner uses special light sensors to ‘capture’ (or photograph) an image and make a digital copy, for example on your screen. You can then use special text or graphics software to work with the scanned image. The most popular types of scanner are flatbed scanners (where the scanner moves the light sensors over the image), and handheld scanners (where a human moves the sensors over the image).

Microphone

A microphone converts sound waves into electrical signals that can be understood by your computer’s sound card. The sound card converts the electrical signals into digital data that your computer can process. For example, you can use a microphone to store speech or music on your computer.

Joystick

A joystick is another kind of pointing device, which is often used for computer games. A joystick has a base, usually with one or more control buttons, and a vertical stem, which can more in any direction to control the movement of an object on the screen. The buttons activate different software features.

Light Pen

A light pen is an input device like a pen that is connected to a computer’s monitor. You can use a light pen to select items and choose commands on the screen by pointing the pen at the screen, and then either pressing a clip on the side of the pen or touching the screen with the pen (the equivalent of performing a mouse click).

Touch Screen

A touch screen is a computer screen which can recognize the location of a touch on its surface. You can touch the screen to make a selection or move a cursor. The simplest type of touch screen is made up of a grid of sensing lines, which sense the vertical and horizontal location of the touch. Touch screens are sometimes used in ATM (banking) machines.

Webcam

A webcam is a small digital movie camera mounted on your PC monitor which allows you to exchange sound and video across the Internet in ‘real time’, i.e., as they are recorded.

Digital Camera

A digital camera is a type of camera that stores photographed images electronically instead of on traditional film. A digital camera uses a special device to capture an image through the lens when you take a picture. The camera stores the image in a storage medium such as a hard disk, which is inside the camera. After the image has been stored, you can transfer it by cable to the computer using software supplied with the camera.

Output Devices

Monitor

A monitor, or computer screen, is a very common type of output device. A monitor displays images which have been generated by the computer’s video card. The monitor is attached to the video card by a cable. There are two main types of monitor: flat panel monitors, and cathode ray tube (CRT) monitors. A flat panel monitor uses a liquid crystal display (LCD) instead of a cathode ray tube to display data. Flat panel monitors occupy much less physical space than CRT monitors.

Printer

A printer is an output device that prints text and computer-generated images onto paper or onto another medium, such as transparent film. There are many different types of printer.

Plotter

A plotter is an output device similar to a printer, but for larger images. Plotters use either pens, or electrostatic charges and special chemicals, to print an image. Pen plotters draw on paper or transparent film with one or more colored pens. Electrostatic plotters ‘draw’ a pattern of electrostatically charged dots on the paper, and then apply chemicals to keep the pattern in place.

Speaker

A speaker is an output device that plays sound generated by your computer’s sound card. The speaker is attached to the sound card by a cable. Most computers also have an internal speaker that is attached to the mainboard and which can play simple sounds

Storage Devices

Hard (Fixed) Disk

Hard disks are the main large data storage area inside your computer. Hard disks are used to store your programs and data

Floppy Disk

Floppy disks are also called diskettes. They are very slow compared to hard disks or CD-ROMs, and hold a smaller amount of data (1.44 megabytes).

CD-ROM

CD-ROM is short for Compact Disc- Read Only Memory. A CD-ROM disk can hold a very large amount of data (usually 650 – 700 megabytes). This is the same as the storage capacity of over 450 floppy disks.

DVD-ROM

DVD stands for Digital Video Disc, or Digital Versatile Disc. A DVD-ROM is like aCD-ROM, but it stores information in a different way so that it has a much bigger capacity than a CD-ROM (about 4.7 or 8.5 gigabytes of data on one side, or 17 gigabytes on a disk with two sides). Because DVD-ROMs can store so much data, they are often used to store movies and animation.

Zip Disk

A Zip disk looks like a floppy disk, but it can hold a lot moredata (up to 100 megabytes). Zip disks can only be read by aspecial drive called a Zip drive. Zip disk technology wasinvented by a company called Iomega.

Magnetic Tape

Computers can read and write data on special cartridges of magnetic tape.A magnetic tape cartridge looks like a music cassette, but it can hold more data. Computer tape cartridges can only be read by a special tape drive. They are often used to make a safe copy of important data that a company or user doesn’t want to lose.