Computer Systems

 1 Chapter  

1 1.1 Overview of Computer Systems  

1.1 The Parts of a Computer System  

 

Let us first look at what a Computer and a Computer System is.  

A computer can be classified as a device that takes in raw data as input and processes it and provides information as the output. The computer also has the ability to store data and information. The computer system consists of hardware (Physical components), software and users (people who use the computer) that are necessary to make the computer function and to processes data in a meaningful way and store data. The physical organisation of devices and the organisation according to functionality of a computer system can be developed by reference to the above definitions.  

 

 

 

 

 

Figure 1.1 and figure 1.2 can be used to illustrate this physical and functional organisation of a computer system. A study of the figure 1.1 and figure 1.2 shows that a computer system has four clear categorisations for hardware and functionality of that hardware. They can be listed as:  

1. Processor, memory and integrating devices  

2. Input devices  

3. Output devices  

4. Storage devices  

 

All hardware components in a computer can be put into one of these four categories. Following are some of the hardware devices that are commonly found in modern day computer. 

 

 Processor, memory and integrating devices  

• Central Processing Unit (CPU)  

• Motherboard or Main board  

• Main Memory  

• Power supply  

• VGA card  

• Sound card  

• LAN Card  

• TV Card  

 

Input Devices  

• Keyboard  

• Pointer device (e.g. Mouse, track-ball)  

• Joystick and Game Pads  

• Scanner  

• Microphones, Still Digital Cameras and Video Cameras   

 

Output Devices  

• Monitor and LCD Panel  

• Printers  

• Speakers  

• Plotters  

 

Storage Devices  

• Hard drives  

• DVD and CD ROM  

• Tape Drives  

• Flash Disks and Memory Cards  

• Floppy disks  

 

Computer Hardware  

This section gives a description of the features and the functionality of the parts of a computer. 

 

 The processor  

The human brain can be considered as the organ that does all the analysis of the information we receive through our five senses: sight, smell, touch, hearing and taste. (figure 1.3) 

 

 

 

It then produces appropriate responses to the information we received. The information received by the brain, the thoughts and ideas it generated is retained in the brain. Further more it is the organ that controls the functionality of our body’s organs and parts. The brain is also capable of independent and creative thought and the generation of new ideas. The human brain learns some of its functionality and control through experience (learning) and some through instinct.  

 The computer’s equivalent to the brain is referred to as the processor. It is capable of receiving information from its input devices and then processing that information and to provide an output (figure 1.4). 

 

 

 

 It also has the capability to store this information in a storage device. The processor is responsible for controlling the various devices of a computer. The major difference of the processor from the human brain is that it is incapable of independent and creative thought and the generation of new ideas. The processor is also incapable of learning. It is a device that can only follow the instructions that have been given to it by the programmer.  

 

There are many manufactures of processors in the world.  

• Intel with their Pentium, Celeron and Xeon Processors, and Advanced Micro Devices Inc. (AMD) with their Duron and Athlon processors are biggest processor manufactures for the PC. 

•  There are other manufactures like Centaur Technologies with their Cyrix processor for the Personal Computer (PC).  

• Sun Micro Systems with their SPARC chip is the company that develops processors for the Sun systems.  

• Where as IBM with their PowerPC and Motorola with their Motorola 6800 are processors manufactures for the Apple computer.  

• The most modern processors being manufactured are the Hyper-threading processors and the 64-bit processors.  

 

Memory  

The memory considered in this section is divided into two basic types.  

• Random Access Memory (RAM) and  

• Read Only Memory (ROM).  

 

The RAM can be explained as a device that temporarily store data. RAM can be read from and also written into. The key feature of the RAM is that when power of the computer is switched off the data in the RAM is lost (Volatile memory). As access to RAM is very much faster than to a permanent storage device, it is an inefficient method to read and write to permanent storage as it will simply slow the processing down a great deal. Therefore during processing it is important  to store programs and data in a temporary storage location. The Main memory has been developed for this purpose. The most common reference to the term ’Memory’ in a computer is when referring to the Main Memory. Main Memory is also referred to as the RAM by many. Read Only Memory (ROM) as implied by the term is a type of memory which can only be read from. This type of memory does not loose its data when the power of the computer is turned off.  

• The most common ROM in the computer is the BIOS (Basic Input Output System) ROM.  

• The CMOS (Complementary Metal Oxide Semiconductor) chip is also belongs to volatile memory since it requires power from a battery to retain the data once the computer is turned off. 

 

 Input and Output Devices  

Input and output devices are the devices of a computer that are used to interact with the user. 

 

 Input devices  

Like the eyes, ears, nose, tong and skin provides a way to sense information about the environment and feed it to the brain, input devices helps the user to provide commands to the processor and also for the processor to receive data and information from its environment. The user can use devices like the keyboard, mouse or trackball and joystick to provide commands and data into the computer. Device like, the microphone, scanner and digital cameras help the processor to receive data from its environment. Any device that can feed data or information to a computer is referred to as an input device.  

 

Output devices  

Similar to body parts being used by the brain to output information and to interact with the environment, the computer uses output devices to output information to the user. All information which is outputted by the processor through the output devices can either be seen, heard or felt. Devices like the Monitor or LCD panel and projectors display information whereas a speaker would provide audible output. A feedback joystick would provide an output which can be felt by the user. Any device that can be used to output information from a computer is known as an output device.  

 

It is also important to note that certain devices have functionality that fall into both input and output categories.  

• For example a touch-screen display and a feedback joystick function as both input devices and output devices.  

 

Storage Devices  

The computer ROM does not have enough capacity to store data, whereas the RAM is volatile and looses data once the power is turned off. Therefore there is a necessity for devices that could store data permanently. Previously data was stored in punch cards (a card with holes punched representing 1s and 0s) before the invention of magnetic storage devices and then optical storage devices. With the improvement of technology it was possible to manufacture devices that could store data in excess of 250 gigabytes (1 bit is a 1 or a 0, 8 bits is 1 byte, 1073741824 bytes is 1 gigabyte). The magnetic tape was one of  the earliest forms of data storage device but had a disadvantage since it had to be accessed in a sequential manner. The introduction of hard disk and floppy disk made it possible for data to be stored and accessed (randomly). The hard disk was not meant to be portable and was known as fixed disk located inside the computer. External hard disks were developed but not for the purpose of portability since they were fragile and prone to strong vibrations. Portable magnetic storage devices like floppy disk had a very limited storage capacity, this was changed with the invention of the ZIP disk which could store over 100 megabytes (1048576 bytes is 1 megabyte). The invention of the optical storage disks like the CD ROM and the DVD ROM made it possible to store data on disks which were not affected by magnetic fields, was easier to transport, and cost effective to produce. The typical CD ROM could store around 700 megabytes whereas the DVD ROM could store in excess of 4.2 gigabytes and now with improved Blu-ray (blue laser) format storage can go up to 27 gigabytes.  

 

The size of all of these disks was somewhat cumbersome (with every device invented in the modern world becoming smaller and much more portable). With this requirement new disk and memory like the flash-drive (pen drive), SD card, Compact-Flash, Sony Memory stick and the XD picture-card have emerged. Some of these devices have a capacity that could exceed 12 gigabytes and are commonly used for storage in small digital devices.  

 

Expansion cards and other components  

The processor, Memory, Input/Output devices and storage devices need to be integrated together to function. These components have to be placed on a board called the Mainboard or the Motherboard. Without this the computer cannot function. Some additional circuit boards may be required to integrate additional devices if they are already not embedded into the motherboard. These circuits are commonly referred to as cards. They are plugged into expansion slots available on the motherboard. Some of the most common cards are the Video Graphics Adapter card, Sound card, Ethernet card, TV card, Data-Fax Modem card, USB card and FireWire card. These cards provide expansion to the motherboard and the ability to connect other input, output and storage devices. There are additional cables that are required to connect devices. Hard disk and floppy drive ribbon cables, CD/DVD drive analog audio cable, video cable, printer cable, USB cables and the FireWire cables are some of the most common cables found in a computer. In addition to the devices mentioned above, there are technologies to connect computers to external devices like mobile phones, PDAs (Personal Digital Assistant) and Laptops. Such technologies create a direct connection between the computer and the external device. Some of the most common technologies are Blue-tooth (wireless), IrDA (infrared) and Wi-Fi (wireless).  

 

 

Chassis and Power supply  

All of the components of a computer system require power to function. Further more computer systems are encased in an enclosure. The units that provide the power and the enclosure are known as the power supply unit and the chassis respectively. There are 7 additional cables that are required to connect the power supply to the wall power outlet and the devices to the power supply. They are the power cables and power connectors.  

 

Chassis  

The chassis consist of space for the motherboard, power supply, input/output connectors, expansion cards, expansion bays, switches and wires to connect them to the motherboard and indicator Light Emitting Diodes (LEDs). The motherboard in an ATX tower casing (figure 1.5) is screwed on to the right side panel of the chassis and the input/output connectors of the main protrude from the rear. The expansion slots are on the bottom right side of the rare. The power supply is located on the top left side of the rear. While the power supply fan helps to cool the power supply, it also sucks out the hot air away from the CPU. 

  

The chassis is usually made from steel, aluminum and/or plastic. Chassis come in various sizes defined using form factors. ATX is one of the most popular form factors, but according to the requirement different form factors may be used (e.g. tower, flatbed). Form factors are a standard in motherboards. The form factor implies the dimensions where the screw holes, CPU, RAM, input/output connectors, expansion slots are located and the type of power connectors. Therefore it is clear that the chassis should have a certain standard. The type of motherboard it supports can be used to refer to the chassis, but there are some exceptions. Hence, a form factor for chassis has been developed according to their specific shape. For example a chassis with an ATX motherboard and an ATX power supply may still take a chassis form factor like tower, flatbed. The tower chassis can be further divided into mini-tower (figure 1.6 ), mid-sized tower (figure 1.7 )and full-size tower (figure 1.8 ). The flatbed chassis can be further divided into desktop (figure 1.9 ) and slim desktop (figure 1.10 ). The tower is taller and much more spacious, where as the flatbeds are more compact and saves occupying space. 

 

 

 

Drive bays  

Drive bays are a part of the chassis which is used to house drives such as the hard disk, CD/DVD Drives and floppy drives. The drive bays come in two standard sizes according to their width.  

They are:  

• 3 inch bay - house the hard disk and the floppy drives usually.  

• 5 inch bay - house the CD/DVD drives The drives housed in these drive bays are held in place using screws.  

 

The drives are connected to the motherboard via data cables and the power is supplied through the power connectors of the power supply. 

 

Power supply  

The power required by the computer system is supplied by the power supply (figure 1.11). The power supply takes in 110 or 230 volts and converts it into voltages ranging from -12 to +12. The voltage selector lets the user select between 110 volts and 230 volts, which is based on the voltage of the main power source. In Sri Lanka it is 230 volts. If you select the wrong voltage it could cause permanent damage to your computer.

The main power is connected to the power supply through a power cable (figure 1.12).  

The power required by the devices is supplied through the power connectors of the power supply. The power connectors come in different shapes and sizes. They also supply different voltages. To avoid the incorrect connection of the power connectors to the devices they usually have special shapes or keys.  

 

Some of the power connectors are listed below (figure 1.13).  

• Mini plug - provides power to the floppy drive  

• Molex power connector - provides power to hard drives, CD/DVD drives and SCSI (Small Computer System Interface) drives  

• Motherboard power connector - These can defer according to the form factor of the motherboard, but their primary task is to provide power to the mother board  

• 12V ATX power connector - this is required to provide additional power to the Pentium 4 processor. This is plugged into the motherboard  

• SATA (Serial Advanced Technology Attachment) power connector - provides power to the SATA hard drive  

 

 Buttons and indicators  

The power button and reset button are located on the front panel of the chassis. The LEDs that indicate the power and the hard disk operation are located on the front panel of the chassis. Most chassis come with a speaker. All the above components are connected the motherboard via a set of wires. Advanced chassis come with chassis intruder detection switches, and panels which indicate the chassis temperature and fan speed.  

 

 

 

1.2 Evolution of computers and Computers today  

 

This chapter discusses the history and the development of the computers. First chapter gives you an idea about the history of computers. Next it gives an explanation about modern day computers. In order to have a complete understanding about computer systems it is quite important to know about how the computer has evolved from its inception.  

 

History  

The history of any area is important in understanding it. Knowledge about the history will give you an overall idea (or the big picture) of how the computers today has evolved to this extent. The knowledge about history will help us in understanding the computers today and the significant milestones they have achieved from its inception.  

 

1.2.1 Key developments  

Many new ideas have contributed significantly to the development of computer systems. Some of the key developments of computer systems from the past are:  

• Abacus - calculating device (3000 BC)  

• Pascaline - mechanical adding machine (1642)  

• Babbage - analytical engine (1830s)  

• Ada - first programmer (1800s)  

• Punched cards - data storage (1800s)  

• Hollerith - tabulating machine (1890s)  

• Mark I - general purpose computer (1944) 12  

• ENIAC - electronic computer (1946)  

• UNIVAC - US Census Department (1951)  

• EDVAC - Stored Program Concept (1951)  

• Generation of Computers  

• Classification of Computers  

• Microprocessor chip  

• Floppy disk for data storage  

• Pocket Calculator  

• Apple II - first personnel computer  

• IBM PC  

• Portable computers  

• Laser Printing and Desktop Publishing  

• Multimedia desktop computers  

• Home video computers  

• Video conferencing  

 

Details in brief  

Abacus (3000 BC): Abacus (figure 2.1) is an ancient calculating device. This is still being used in China, Russia and the Far East.

 

 

Pascaline (1642):  

Pascaline (figure 2.2) is a desktop mechanical adding machine. This was developed by Blaise Pascal. Figure 1.15: Pascaline  

 

Analytical Engine (1830s):  

This was invented by Charles Babbage who is known as “the father of computers”. Designed to store one thousand 50 digit numbers for calculations and decisions (figure 2.3). 

 

Ada (1800s): This is probably the world’s first computer programmer. Collaborated with Charles Babbage.  

 

Punched Cards (1800s): A card punched with holes (figure 2.4) in certain places so that a computer can read data coded from the combination of holes. This was first used by Joseph Jacquard to automate his weaving factory. 

 

 Tabulating machine (1890s): This was invented by Herman Hollerith to tabulate 1890 US census data. It was electrically powered and, used punched cards.   

Mark I (1944): This was invented in 1944 by Dr. Howard Aiken. The idea is based on programmable, general purpose computer (figures 2.5,2.6) .  

 

  

 

 

The following data with the years will give us a good understanding as how computers have evolved over the past.  

 

• In 1642 Biaise Pascal introduced the Pascaline digital machine.  

• In 1822 Charlet Babbage introduces the Difference Engine and later the Analytical Engine (as he called them), a general purpose computing machine.  

• In 1937 John V. Atanasoff created the Atanasoff-Berry Computer (ABC). This is considered as the first electronic computer.  

• In 1945 John von Neuman specified the architecture of the EDVAC, which introduced the stored-program computer concept.  

• In 1946 John Mauchly and J. Presper Eckert introduced the ENIAC, an electronic computing machine.  

• In 1947 William Shockley, Walter Brattain and John Bardeen was successful in testing the point-contact transistor. This made the semiconductor revolution which helped to reduce the size of computers.  

• In 1949 Maurice Wilkes at Cambridge University released the EDSAC, the first real stored-program computer.  

• In 1952 UNIVAC I was developed and this is the first commercial computer which got a large amount of public attention.  

• In 1953 IBM releases the IBM 701. This is IBMs first electronic computer.  

• In 1955 Bell laboratories introduced the TRADIC, the first fully transistorized computer.  

• In 1958 Jack Kilby at Texas Instruments created the first integrated circuit (IC).  

• In 1969 the ARPAnet was developed. (This became the base for Internet later.)  

• In 1971 IBM invented the 8” floppy disk.  

• In 1972 Intel introduced the Intel 8008 microprocessor.  

• In 1973 Robert Metcalfe introduced the Ethernet method for network connections.  

• In 1974 Xerox Palo Alto Research Centre designed the first workstation with mouse input available.  

• In 1977 Apple Computers introduced Apple II.  

• In 1979 Motorola introduced the 68000 microprocessor. 16  

• In 1980 Segate Technology created the first hard disk drive for microcomputers.  

• In 1981 Xerox introduced the Star, the first personal computer with a graphical user interface (GUI).  

• In 1981 Sony introduced the 3 " floppy drives.  

• In 1982 Sony introduced the first CD player.  

• In 1984 Apple Computer introduced the Macintosh, the first successful mouse driven, GUI based computer.  

• In 1984 IBM released the personal computer PC-AT. This introduced the 16-bit ISA bus and is the computer which all modern personal computers are based.  

• In 1985 Philips introduced the first CD-ROM drive.  

• In 1987 IBM introduced its PS/2 machines. This machine made the 3 " floppy disk drives and VGA video standards for personal computers.  

• In 1988 EISA architecture was developed.  

• In 1990 the World Wide Web (WWW) was introduced. Hyper Text Markup Language (HTML) also was introduced.  

• In 1995 Microsoft introduced the Windows 95 operating system. This is the first main 32-bit operating system.  

• In 1997 Intel released the Pentium II microprocessor.  

• In 1997 AMD released the K6 microprocessor.  

• In 1998 Microsoft released Windows 98.  

• In 1999 Intel released the Pentium III, with SSE (Streaming SIMD Extensions) added.  

• In 1999 AMD released Athlon.  

• In 2000 Microsoft released Windows Me and Windows 2000.  

• In 2000 both Intel and AMD released processor at 1 GHz.  

• In 2000 Intel released Pentium 4. It belongs to Intel Architecture 32-bit (IA-32) family.  

• In 2001 Intel released the Itanium processor. This is Intel’s 64-bit processor for personal computers.  

• In 2001 Microsoft released Windows XP.  

• In 2002 Intel released the Pentium 4 with 3GHz speed. This processor also included the Hyper-Threading (HT) technology.  

• In 2003 Intel released the Pentium M, a processor designed for mobile computer systems. • In 2005 Intel released the dual core processor named Core Duo  

 

 

1.2.2 The mechanical computer 

 Charles Babbage a Mathematics professor is considered as the father of computers. In 1822 Charles Babbage invented the Difference Engine (figure 2.7) and later the 17 Analytical Engine, which was general-purpose computing machine. The Analytical Engine was designed to store one thousand 50 digit numbers (words) for calculations and decisions. It had a storage capacity (memory) of 1000 such numbers. It included built-in functions that a general purpose computer would need. It also included conditional functions to change the order of instructions execution (otherwise instructions would be executed in numerical sequence). The Analytical Engine also used punch cards to program the machine. It operated using steam power.  

 

 The Analytical Engine included the units which a general purpose computer has today. Therefore it is considered the real predecessor for general purpose computers used today.  

The units included were:  

• An input device: Punched cards provided the input.  

• A control unit: A unit used to control or program the processor.  

• A processor (or calculator) : A unit which consisted mechanical parts to process data.  

• Storage: A unit which could hold 1000 50-digit numbers.  

• An output device: Used to print the final results.  

 

Any how this computer was not completed, due to the problems of the technology availability at this period. 

 

 

1.2.1 Electronic computers based on digital switching  

The first true digital electronic computer was created by John V Atanasoff during 1937- 1942. The Atanasoff-Berry Computer (called ABC figure 2.8) was the first to use modern digital switching techniques. Vacuum tubes were used as switches (the needs of switches are explained later). The concepts of using binary arithmetic and logic circuits were introduced to computing world by this ABC.  

The first large-scale electronic computer for the military which was named as ENIAC (Electrical Numerical Integrator and Calculator figure 2.9) was invented in 1946 by John Presper Eckert and John William Mauchly. This was a valve based computer and now referred to as a first generation computer. ENIAC had the following characteristics: • Operated on 10-digit numbers and could multiply two such numbers at the rate of 300 products per second. • Was about 1000 times faster than the previous generation of electromechanical relay computers. • Was a valve based computer. • Used approximately 18,000 vacuum tubes, and occupied 1,800 square feet of floor space and consumed around 180,000 watts of electrical power. • Punch cards were used as input and output and registers served as adders and also as quick-access read/write storage. • The executable instructions of a program were created using specified wiring and switches that controlled the flow of computations through the machine. AS such, ENIAC had to be rewired and switched for each program to be run.  

John Von Neumann introduced the idea of using the computer as a fixed physical structure and to use programmed control, without the need for any change in hardware. This allowed executing many different programs (tasks) without changing the physical structure of the computer. The Von Neumann’s idea is known as the “stored-program technique" (figure 2.10. This idea became the base for the future generation high-speed computers and is used by modern day computers.  

 

 1.2.2 UNIVAC to the modern day computers  

 

At around 1947 computers started to use these ideas mentioned above such as storedprogram technique. They are now considered as first generation computers. Some machines introduced at this time are EDVAC and UNIVAC (Universal Automatic Computer figure 2.11). These computers used the concept of RAM (Random Access Memory) for the first time. The RAM was used to store programs and data when the computer is functioning. They used the machine language to write programs and later computers started to use high-level languages. UNIVAC was the first true generalpurpose computer which was able to manipulate both alphabetical and numerical programs. This made computers available not only for science and military, but also for business.  

From UNIVAC to today, computers have developed and changed a lot. The first generation computers used vacuum tubes in their construction and today we use integrated circuits which are much smaller and more efficient. The computers are using a mode of on/off when it is functioning. This is called as the binary system since it represent 1 and 0, or true and false. To implement this, an efficient switch is required. A digital computer needs a large number of such switches. The first electronic computers used vacuum tubes (figure 2.12) as switches, and although the tubes worked they had many problems.  

Early computers used a type of tube called “triode" (three pin vacuum tube). This tube was not that much good to be used as a switch. It needed a lot of electrical power and generated a massive amount of heat and in-turn lead to the tube to fail frequently. The invention of the transistor (figure 2.13) made a revolution of computers. The size of the transistor was very small and in-turn made the size of the computer much smaller. The transistor was much faster than the earlier computers built using vacuum tubes and was much more reliable. Compared to the tube, transistor was much more efficient as a switch. 

 

The invention of the transistor and then the conversion from tubes to transistors has lead to greatly reducing the size of computers used today. The introduced of integrated circuits (figure 2.14) which contains millions of transistors in a small pack, have made the computers more and more smaller in size. Some computers today are very small in size which would even fit on to a palm of a person and consumes very little amount of power (provided using batteries). This is a great improvement compared to computers which we had at the earlier days which filled large room spaces and consumed huge amounts of electrical power. Today most of the consumer applications have replaced vacuum tubes with transistors and integrated circuits . But still vacuum tubes are used for high-end audio applications because they produce a warmer and richer sound than transistors do.  

 Modern computers use integrated circuits (ICs), but not individual transistors. An integrated circuit consists of multi-millions of transistors. (Note that the first integrated circuit contained only six transistors in it). In June 2001, Intel researchers invented the world’s smallest transistor. This will allow billions of transistors to be packed in a very small unit and in-turn reduce the size of the computer largely. In year 2003 AMD Athlon 64 processor (figure 2.15) was introduced with more than 105.9 million transistors and Pentium 4 Extreme Edition (figure 2.16) processor was introduced with more than 178 million transistors.  

 

Microprocessor history  

The processor (also known as the microprocessor or Central Processing Unit (CPU)) is the heart of a computer system. The processor is the unit which performs all the calculations (the processing) in a computer system. The processor also controls the other units in the computer system.  

 

The following lists some of the important details about the history of microprocessors and how they have evolved.  

• In 1970, Intel introduced a 1Kb memory chip. This was very much large than what was available at that time. It was known as 1103 (figure 2.17) Dynamic Random Access Memory (DRAM). By next year this became the world’s most selling semiconductor device. Intel was recognised as a successful memory chip company in the 1970s. In 1971 Intel introduced the 4-bit Intel 4004 (figure 2.18) microcomputer set (however the term microprocessor was not used until later). This was very small in size and contained 2,300 transistors. This delivered as much as computing power as ENIAC. When you compare the two ENIAC used 18,000 vacuum tubes and used 3000 cubic feet in size when it was built in 1946. The Intel 4004 microprocessor executed at 108 KHz and was able to execute 60,000 operations per second.  

 

Note: Hz is a unit used to measure the speed of a microprocessor. (It is the number of clock cycles per second) • Intel introduced the 8008 microcomputer in 1972, which processed 8 bits of information at a time, twice as much as the original chip. By 1981, Intel’s microprocessor family had grown to include the 16-bit 8086 and the 8-bit 8088 processors. These two products lead to the production of the first PC, a product from IBM. • In 1982 Intel introduced the 286 chip. The 286 offered software compatibility with its predecessors. This chip was first used in IBM’s PC-AT, the system upon which all modern PCs are based. • In 1985 the Intel 386 processor was released with a new 32-bit architecture. The chip could perform more than five million instructions per second (MIPS). Compaq’s DESKPRO 386 was the first PC based on this microprocessor. • In 1989 the Intel 486 processors was released. This had the first built-in math coprocessor. This equalled the performance of some of the mainframe computers. (mainframe computers are explained later in this chapter) • In 1993 Intel introduced the first P5 family (586) processor called the Pentium. The Pentium processor executes up to 90 MIPS (Million Instructions per Second). Note: Intel changed from using numbers (386/486) to names (Pentium/Pentium Pro) for its processors and this was based on the fact that it could not secure a registered trademark on a number and therefore could not prevent its competitors from using those same numbers on similar chip designs) • In 1995 the first processor in the P6 (686) family, called the Pentium Pro processor was introduced. It was the first to be packaged with a second die containing highspeed L2 memory cache to accelerate performance. (Cache memory is explained in a later chapter) • In 1997 Intel revised the original P6 (686/Pentium Pro) and introduced the Pentium II processor (figure 2.20). Pentium II processors had its transistors packed into a cartridge rather than a conventional chip, allowing them to attach the L2 cache chips directly on the module. The Pentium II family was augmented in April 1998, with both the low-cost Celeron processor (figure 2.22) for basic PCs and the high-end Pentium II Xeon processor (figure 2.19) for servers and workstations. Intel followed with the Pentium III in 1999, essentially a Pentium II with Streaming SIMD Extensions (SSE) added. 

 

Note: SSE represents a set of instructions integrated into Intel’s Pentium III (figure 2.21) CPUs. They are intended to speed up CPU performance. SSE appears to offer significant improvements.  

 

• At the same time, AMD (Advance Micro Devices - another company) introduced its processor called AMD K6 (figure 2.23). The K6 was both hardware and software compatible with the Pentium, meaning it could be plugged to the same socket and could run the same programs. AMD continued making faster versions of the K6 and made a huge way in the low-end PC market by providing low-cost processors.  

 • In 1999 AMD introduced the Athlon to compete with Intel in high-end desktop PC market. Athlon required a motherboard with an Athlon supporting chipset and processor socket. • In 2000 AMD introduced both its Athlon Thunderbird and Duron processors. • In 2000 Intel introduced the Pentium 4 which is a 32-bit processor. • In 2003 AMD released its first 64-bit processor which is Athlon 64.  

 

Generations of Computers  

The development of computers and the consideration of key developments have enabled computers to be categorised into various generations. Following is a summary of the generations of computers.  

 

First Generation (1951-1958)  

• Used vacuum tubes (figure 2.12) for internal operations • Used low-Level languages for programming (machine language) • Used magnetic drums for primary memory. • Primary memory was limited. • Heat and maintenance problems were there. • Used punch cards for input and outputs. • Input and output was slow. • e.g. UNIVAC I, EDVAC  

 

Second Generation (1958-1964)  

• Used transistors (figure 2.13) for internal operations. • Increased use of high level languages. • Used magnetic cores for primary memory. • Increased memory capacity. • Binary coded data were used. (concept of binary is explained later) • Increasing processing speed. • Used magnetic tapes and disks for secondary storage E.g. IBM 1620 (figure 2.24), UNIVAC 1108. Figure 1.37: IMB 1620  

 

Third Generation (1965-1970)  

• Used (ICs) (figure 2.14) on silicon chips for internal operations. • Memory capacity was increased. • Minicomputers became a common use. • Software industry emerged. • Reduction in size and cost of computers happened. • Increase in speed and reliability. E.g. HONEY WELL-6000 SERIES (figure 2.25)  

 

Fourth Generation (1971-today)  

• Used Large Scale Integration (LSI) and Very Large Scale Integration (VLSI) for internal operations. • Development of the microprocessor happened. • Introductions of micro and super computers. • Increase in speed, power and storage capacity. • Parallel processing was introduced. • Artificial intelligence and expert systems were introduced. • Robotics was introduced. • Increased use of Micro/Personal Computers. E.g. Apple II (figure 2.26), IBM PC (figure 2.27), Micro Computers  

 

Fifth Generation (1981-1990s)  

• A project to develop intelligent computers. • They are computers with artificial intelligence. • Symbolic manipulation and symbolic reasoning is required.  

 

Personal Computers  

The Personal Computers (PC) is one of the most commonly used computer types in the world. In 1975 IBM introduced its first personal computer (PC). The PC named Model 5100 (figure 2.28) had 16Kb of memory, a built-in 16 x 64 character display, and a builtin BASIC language interpreter.  

 

 Started from here, today there are many different PCs available in the market. The PCs have evolved a lot by today compared to its inception in 1975. Today IBM PCs are based on microprocessors such as Intel Pentium 4 etc. The original PC had one or two single sided floppy drives that stored 160Kb and today we have PCs which have even 200Gb of disk space. IBM originated the development of PCs and today there are many other companies who dominate in the PC industry such as Microsoft, Intel, and AMD etc.  

 

1.3 Modern day computers  

Modern day computers are much advanced than earlier computers. They help us in our day to day life, to get most of our tasks done. Today there are many different categories of computer systems available, such as: • Supercomputers • Mainframe computers • Minicomputers • Network servers • Personal computers Now we will look at each of these categories.  

 

1.3.1 Supercomputers  

Supercomputers (figure 2.30) are the most powerful computer systems available. Supercomputers are sophisticated, expensive computers, using state-of-the-art technology (modern technology at its best). Supercomputers are designed to perform large amounts of workloads and are used by researcher organisations, universities and by organisations which perform tasks which require enormous amount of computing power. Supercomputers are used in the simulation and modelling of complex systems. E.g. weather, chemical processes, US economic predictions, motion of galaxies. A supercomputer may have thousands of microprocessors in it and provides processing speeds, many times that of your home computer.   

 

1.3.2 Mainframe computers  

Mainframe (figure 2.31) computers are large powerful systems. Users connect to a mainframe computer and access the resources of the mainframe computer through a device called a terminal (figure 2.32). Terminals are of two types which are dumb terminals and intelligent terminals. Dumb terminals do not do any processing, it is used to connect and get tasks done by using the resources (processor, memory, storage) of the mainframe computer. In contrast an intelligent terminal has some limited processing power, but mostly don’t have the capability of storing data. You can also use a standard personal computer to connect to the mainframe as it is done in some working environments. A large mainframe computer can handle even more than 1000 users at a given time. For example an airline company can use a mainframe computer to handle its flight reservation systems, where some times large no of users might connect to the system at a given time. However mainframe systems are less flexible to use. In use they are mostly dedicated to handler a single task or maybe a few tasks. That means mostly the mainframe is configured to handle a particular task so that the full utilisation of the mainframe computer can be used for processing that task. For example: • A bank to handle the banking system • An airline to handler the flight reservation system • A country’s motor department to store the details about registered vehicles  

 

1.3.3 Minicomputers  

Minicomputers (figure 2.33) are computer systems which are less powerful than mainframe computers but more powerful than personal computers. They got the name because they were much small in size compared to the other computers at that time. Like mainframe computers, minicomputers also can handle many users at a time (can serve the needs of hundreds of users at the same time). You can connect to a minicomputer either by using a terminal or a personal computer.  

 

 1.3.4 Network Servers  

Organisations today use personal computers connected through a computer network (A computer network is a set of computers connected together so that they can share data and resources, access (communicate/talk) to the other computers in the network etc). When personal computers are connected through a computer network there should be a computer (which may also be a personal computer) to manage and supervise the computer network. Such a computer is known as Network Server (figure 2.34). Because personal computers are general purpose computers, when an organisation has a computer network with personal computers it is very flexible. The uses of servers include: • For the purpose of using email (i.e. as a email server) • To connect to the Internet (i.e. as the proxy server) • To share files (i.e. as the file server) • To connect to a printer (i.e. as the printer server) • To connect to a database (i.e. as the database server) Note: A database is a software used to store and manage data in a much more organised way, as opposed to using normal files to store data. Depending on how the network server is setup many users can connect to the network server to get various tasks done. Mostly in an office the employees will have a personal computer or a laptop on their desk and they will use this personal computer to connect to the network.  

 

1.3.5 Personal computers and Microcomputers 

 Computers which are designed to be used by a single person are known as Personal Computers (PCs). Personal computers have been very popular due it’s small size and its ability to act as a general purpose machine. Most of the companies today assign personal computers to their employees to get done office work such as typing letters, drawing charts, performing day to day business transactions. Also today you find personal computers used at home by individual users. Personal computers are shared some times among students at places like universities, institutions. But only one person can use the computer at a time, which is one of the main characteristic of a personal computer. Personal computers are some times referred as microcomputers because their smaller size. The following are some types of personal computers. • Desktop computers • Workstations • Notebook computers • Tablet PCs • Hand-held personal computers • Smart phones  

 

1.3.5.1 Desktop computers  

Desktop computers are a type of a personal computer and as the name implies it is meant to be placed on a desk or a table. Desktop computers are not meant to be carried around. Desktop computers are very popular among organisations. Organisations provide desktop computers to their employees to improve the work efficiency of the employees. Normally a desktop computer is meant to be used by a single user, but is mostly shared in real use, for example in a university or in a school, desktop computer are shared by students, but only one user at a time. There are two kinds of desktop computers. One is a horizontal aligned flatbed (figure 2.35) type system and the other a vertical oriented tower (figure 2.36) type system. Desktop computers comprise a system unit which contains important parts of a computer system such as the microprocessor, hard disk, memory, floppy disk driver etc.  

 

1.3.5.2 Workstations  

Workstations (figure 2.37) are a personal computer type which is powerful than desktop computers. It is a specialised computer mostly used by a single user. Workstations are most popular among scientists, video production crowd, animators, engineering designers etc due to its powerful capabilities and ability to perform complex tasks much faster. 

 

1.5.3.3 Notebook computers and Tablet PCs  

As the name implies notebook computers (figure 2.38) takes the shape of a thin book. Notebook computers are very portable and some times are known as mobile computers because they can be carried with you (as opposed to desktop computers). These computers have less weight. To use it you can open up the cover (the upper part) of the notebook computer and then you get a thin display screen. The computer can be folded when not in use to make it more portable. Notebook computers are very popular among professional since they can carry it for meetings and workshops. These computers when in use could be kept on the lap and hence are also known as laptop computers. These notebook computers operate on the AC power and also can be used with a battery which comes with the computer.  

 Tablet PCs (figure 2.39) are full equipped mobile computers which have all the features of a notebook computer plus more. It is more light weight than notebook computers and is very popular among people who travel and need to take notes while the computer is in hand (like architects). Tablet PCs have a special pen which they can use for this purpose. This special pen is known as the stylus or digital pen and the screen is touch-sensitive. You can use this pen to take notes on your computer and also to select and click certain icons. Some Tablet PCs have a microphone build in to take voice input and also can be connected to a network. Tablet PCs run special versions of certain software programs.  

 

 1.5.3.4 Hand-held personal computers  

As the name implies it fits in to your hand. They look like a very small note book and are in the same size as of a small note book. Hand-held personal computers are used mainly for purposes such as: • taking notes • to have your phone book contacts and address book contacts • to have your appointment organiser • to access a day calendar Hand-held personal computers also have a special pen. You can write on the screen using this pen. For example when you want to take notes you can use this special pen. Some times you also get a tiny keyboard as well. Hand-held personal computers can also connect to a network and the Internet. Latest Hand-held personal computers have facilities of mobile phones and music players. One popular type of a Hand-help personal computer is the Personal Digital Assistant (PDA). PDAs (figure 2.40) have all the features described above for a Hand-held personal computer.  

 

1.5.3.5 Smart phones  

Smart phones are special featured mobile phones. Smart phones are much bigger when compared to a normal phone. Some smart phones even have a tiny keyboard. Smart phones have some special features such as Internet and email facility, calendar facility, personal organiser facility etc. Also some smart phones have built-in digital cameras and music players.