What is a computer System…….?

 What is a computer System…….?

“A computer system is the synthesis of hardware and software”. A typical computer system employs a computer that uses programmable devices to store, retrieve, and process data.

A computer is a machine that stores knowledge in its memory, and does automated calculation on that knowledge. Automated calculation means that if the machine is given some input, it will product some output.

The term Computer Hardware refers to all the devices that form the computer or connected to the computer that you can physically touch. Hence, the computer screen, the printer, the mouse, and speakers are computer hardware.

                                                                                                 A Computer System

·        Von Neumann’s PC Structure

 The modern microcomputer has roots going back to USA in the 1940’s. Of the many researchers, the Hungarian-born mathematician, John Von Neumann (1903-57), is worthy of special mention. He developed a very basic model for computers which we are still using today.

John Von Neumann (193-57) progenitor of the modern, electronic PC.

Von Neumann divided a computer’s hardware into 5 primary groups.

·        CPU

·        Input

·        Output

·        Working Storage

·        Permanent Storage

This divided provided the actual foundation for the modern PC, as von Neumann was the first person to construct a computer which had working storage (what we today call RAM). And the amazing thing is, his model is still completely applicable today. If we apply the Von Neumann model to today’s PC, it looks likes this:

Advantages of Computer System

• Speed
• Accuracy
• Reliability
• Diligence
• Versatility
• Artificial Intelligence

Classifications of Computer

Classifications 1

Computers: Analog (ECG), Digital (PC), Hybrid (Super Com.)

Classifications 2

Mini (Single user), Micro (Multi user, <100), Mainframe (Multi user, <100)

Classifications 3

Special Purpose Computers (ECG), Multipurpose Computer (PC)

Computer Generations (History)

Computer Generations (History)

The history of computer development is often referred to in reference to the different generations of computing devices. Each generation of computer is characterized by a major technological development that fundamentally changed the way computers operate, resulting in increasingly smaller, cheaper, and more powerful and more efficient and reliable devices.

Computer Generation

Computer Generation

1^st Generation (1940-1956)-Vacuum Tubes

              The first computer used Vacuum Tubes for circuitry and magnetic drums for memory, and was often enormous, taking up entire rooms. They were very expensive to operate and in addition to using a great deal of electricity, generated a lot of heat, which was often the cause of malfunctions. First generation computer relived on machine language to perform operations, and they could only solve one problem at a time. Input was based on punched cards and paper tape, and output was displayed on printouts. 

              The UNIAC (UNIVersal Automatic Computer) and ENIAC (Electronic Numerical Integrator and Computer) computers are examples of first-generation computing devices. The UNIVAC was the first commercial computer delivered to a business client, the U.S. Census Bureau in 1951.   

2^nd Generation (1956-1963)-Transistors

            Transistors replaced vacuum tubes and used in the second generation of computers. The transistor was invented in 1947 but did not see widespread use in computers until the late 50s. The transistor was far superior to the vacuum tubes, allowing computers to become smaller, faster, cheaper, more energy-efficient and more reliable then their first generation predecessors. Though the transistor still generated a great deal of heat that subjected the computer to damage, it was a vast improvement over the vacuum tube. Second-generation computers still relied on punched card for input and printout for output.

               Second-generation computers moved form cryptic binary machine language to symbolic, language, which allowed programming to specify instructions in words. High-level programming languages were also being developed at this time, such as early versions of COBOL and FORTRAN. These were also the first computers that stored their instructions in their memory, which moved form a magnetic drum to magnetic core technology. The first computers of this generation were developed for the atomic energy industry.

      

 3^rd Generation (1964-1967)-Integrated Circuits

            

               The development of the integrated circuits was the hallmark of the third generation computers of computers. Transistor were miniaturized and place on silicon chips, called semiconductors which drastically increased the spend and efficiency of computers.

                Instead of punched card and printouts, user interacted with third generation computer through keyboard and monitors and interfaced with an operating system, which allowed the device to run many different applications at one time with a central program that monitored the memory computers for the first time became accessible to a mass audience because they were smaller and cheaper than their predecessors.

4^th Generation (1971-present) Microprocessors

               The microprocessors brought the fourth generation of computers, as thousands of integrated circuits were built onto a single silicon chip, what in the first generation filled and entire room could now fit in the palm of the hand. The Intel 4004 chip, developed in 1971, located all the components of the computer-form the central processing unit and memory to input/output controls-on a single chip.                 

5^th Generation (Present and Beyond) Artificial Intelligence

  

               Fifth generation computing devices, based no artificial intelligence, are still in development, though there are some application, such as voice recognition, that are being used today. The use of parallel processing & superconductors is helping to mark artificial intelligence a reality. Quantum computation &

                 Molecular & nano technology will radically change the face of computers in yes to come. The goal of fifth-generation computing is to develop devices that respond to natural language input & are capable of learning & self-organization.

v     laptop and palmtop computer

BUSES

BUSES

             In computer architecture, a bus is a “subsystem that transfers data between computer components inside a computer” or between computers. Each bus defines its set of connectors to physically plug devices, cards or cables together.

      Data bus- The channel, which carries data between the processor and other device in both directions.

      Address bus- The channel, which carries the address indicating form/to where date should be read/written. (Mainly work between CPU&RAM)

      Control bus- The channel, which carries the control single form the CPU to other devices. (Control- check the status of the device whether 1or 0)

Ø   Discuss: Bus speed

Serial & Parallel Data Transmission

            

              Serial: Term used to describe the process of transmitting information one bit at a time, or sequentially.

               Parallel: Action that is performed at the same time as another. For example, a communication that sends multiple bits of data each second.

INTERNAL BUSES

Term used to describe a device that is installed within the computer

EXTERNAL BUSES

 Also known as an”input/output bus” or “0/1 bus,” it is the “data pathway that connects peripheral devices to the CPU”.

  ISA (Industry Standard Architecture): This bus is the 16-bit ISA slot low speed work horse of the system. You will commonly fine a sound card hooked up this type BUS.

 PIC (Peripheral Component Interconnect): Support 32-64 bit bus and is  the reigning standard of external buses. The PIC is fast and is slowly marking the ISA fade away. Go with a PIC Bus Card when possible.

 IDE (Intelligent Drives Electronics): This bus is used mostly for disk drives and connects up to two devices on one connection. More than likely you’re hard drive and CD-ROM are connected through this type bus.

AGP (Accelerated Graphics Port): This bus provides form 2 to 4 times the speed of the PIC and is used for video expansion only. If you have this slot on your motherboard make sure and use it for you video card. This is great way to go and takes a lot of stress off the CPU, thus gaining in performance all the way around.

Data Representation

 Data Representation

One of the major problems we face in using a digital computer is communicating with it. We must have one or more ways of getting data into the computer to be processed. There are several types of input devices that read data into a computer. But hoe does one prepare the data to be used as input….? How do we convert human-readable documents into a computer-readable form, and what type of input media do we use…? Well, as you probably suspect, there are several ways to perform this conversion process.

Number Systems

The term number system refers to the schemes implemented in digital computer and calculator hardware and software to represent numbers. Different numbers systems such as Decimal, Binary, Octal and Hexadecimal are used by people. A number system has Base/Radix and there are several symbols which are used as digits.

Number of symbols in the number system is equal to the value of the base. The value of each digit determined by the symbol used and the position where it appears (position value)

Decimal Number System

Decimal Number System

When we write decimal (base 10) numbers, we use a positional system. Each digit is multiplied by an appropriate power of 10 depending on position in the number:

For example:

                     843 = (8*­_10­­2) + (4*₁₀1) + (3*₁₀0)

                            = 8*100 + 4*10 + 3*1

                            = 800 + 40 + 3

In the decimal number system, there are ten possible values that can appear in each digit position, and so there are ten numerals the familiar zero though nine (0,1,2,3,4,5,6,7,8,9). In a positional national system, the number base is called the radix. Thus, the base 10 system that we normally use has a radix of 10. The term radix and base can be use interchangeably. When writing numbers in a radix other then ten, or where the radix isn’t clear form the context, it is customary to specify the radix using a subscript. Thus, in a case where the radix isn’t understood, decimal numbers would be written like this:

127₁₀ 11₁₀ 5673₁₀

Generally, the radix will be understood form the context and specification is left off.

 Binary Number System

 The binary number is also a positional notation numbering system, but in this case, the base is not ten, but is instead two. Each digit position in a binary number represents a power of two. So, when write a binary number, each binary digit is multiplied by an appropriate power of 2 based on the position in the number.

For example:

                  101101 = 1*₂5 + 0*₂4 + 1*₂3 + 1*₂2 + 0*₂1 + 1*₂0

                               = 1*32 + 0*16 + 1*8 + 1*4 + 0*2 + 1*1

                               = 32 + 8 + 4 + 1

  In the binary number system, there are only two possible values that can appear in each digit position rather than the ten that can appear in a decimal number. Only the numerals 0 and 1 are used in binary numbers. The term ‘bit’ is a contraction of the words “binary” and “digit”, and when talking about binary numbers, it is often necessary to talk of the number of bits used to store or represent the number. This merely describes the number of binary digits that would be required to write the number. The number in the above examples is a 6 bit number.

The following are some additional example of binary numbers.

                      101101₂   11₂   10110₂

 Octal (base 8) Number System

The octal number system is used to represent binary numbers in a form which is more readable to human beings. Instead of using only two symbols and many digits, eight separate symbols 0 to 7 are used to represent groups of three binary digits. One difficulty with octal however is that most computers tend to use word lengths which are multiples of four rather than three bits. As a result data word cannot generally be expressed as an exact number of octal digits.

Hexadecimal (Base 16) Number System

 In the hexadecimal number system the number 0-9 are represented in their normal way, but numbers 10-15 are represent by the letters A-F respectively. Each hexadecimal digit is thus equivalent to four binary digits and a word of eight bits (byte) can be expressed exactly by to hex digits.

Number System Conversions

Number System Conversions

Integer part

Divide the quotient repeatedly by the target base which recording the remainders until the quotient becomes zero.

Write the remainders form bottom to top as the digits form MSB to LSB.

Fraction part

Repeatedly multiply the fraction part by the target base value while recoding the integer values until the fraction become zero or until the required number of fractional positions are found.

Write the integer values form top to bottom.

Example 01:

Bin, Oct, Hex - - Decimal

Bin, Oct, Hex - -    Decimal

• Converting form Binary to Decimal            

               

1	0	0	1	0	0	1
2­6	25	24	23	22	21	20
64	32	16	8	4	2	1
64  +  0  +  0  +  8  +  0  +  0  +  1
7310

­

• Converting form Octal to Decimal        

Example: Convert 547.2₈ to Decimal

5	4	7	.2
82	81	80	8-1
64	8	1	0.125
320  +  32  +  7  +  0.250
3592510

• Converting form Hexadecimal to Decimal      

Example: Convert 1A5F₁₆ to decimal

1	A	5	F
163	162	161	160
4096	256	16	1
4096  +  2560  +  80  +  15
675110

Decimal – Bin, Oct, Hex

 Decimal – Bin, Oct, Hex

• Converting from Decimal to Binary

Perform successive division by 2, placing the remainder (0 or 1) in each of the position form right to left.

Continue until the quotient is zero.

Example 01: 44₁₀ - Binary

• Converting from Decimal to Hexadecimal

Perform successive divisions by 16, placing the remainder (0-9)-F) in each of the position form right to left

Continue until the quotient zero.

Octal - Binary

Octal    -    Binary  

Each octal digit can be represented by three binary digits as shown by the table below.

         

Octal	Binary
0	000
1	001
2	010
3	011
4	100
5	101
6	110
7	111

                                            

Ø   To convent octal to binary, each octal digit should be replaced by a 3 bit binary equivalent.

Ø   To convent binary to octal, group of three bits should be formed starting form the decimal point in both directions and replace each by the equivalent octal digit

Example 01:

                      256.48₈ – Binary

                         2         5         6        4       7

                         010    101     110    100    111

                     256.47₈ = 01010110.100111₂

Example 02:

                      11010011011.11001₂

                   

011          010       011       011.      110     010 

   3             2           3           3.         6         2

11010011011.11001₂ = 3233.62₈

System Software and Application Software

System Software and Application Software

Computer software is a general term use to describe “a collection of computer programs, procedures and documentation that perform some tasks on a computer system”. The term includes application software such as word processors which perform productive tasks for user, system software such as operation system which interface with hardware to provide the necessary services for application software, and middleware which controls and co-ordinates distribute system.

System software is any “computer software which manages and controls computer hardware so that application software can perform a task”. Operating systems, such as Microsoft Windows, Mac OS or Linux, are prominent example of system software.

Application software is a subclass of computer software that “employs the capabilities of a computer directly and thoroughly (completely) to a task that the user wishes to perform”. In this context the term application refers to both the application software and its implementation. Typical examples software applications are word processors, spreadsheet, and media players.

Operating system: “the software component of a computer system that is responsible for the management and coordination of activities and the sharing of the resourced of the computer”. The operating system (OS) acts as host for application programs that are run on the machine.

Operating System Classifications

Operating System Classifications

Classification 1
Single user (Single taking) E.g.: PC DOS(IMB), MS DOS(MIC)	Single user (Multi taking) E.g.: Win98, Mac,		Multi user (Multi taking) E.g.: OS-400, Unix, Xp, Vista, 200
Classification 2
CLI(Command Line Interface E.g.: Dos, Unix		GUI(Graphical User Interface) E.g.: Win, Mac
Classification 3
Desktop Operating System E.g.: Win 9x, Xp		NOS(Network Operating System) E.g.: Win NT, 2000, 2003

Internal & External Components of a PC

Components of a PC Internal                          External
Motherboard	Monitor
Processor	Keyboard
Hard Disk	Mouse
Floppy Disk Drive	Speaker
CD ROM	CPU
VGA Adapter	Printer
Modem	Scanner
Sound Card	Web cam
Network Adapter	Light pen

Storage Devices

Storage Devices

A storage device is a “hardware device designed to store information”. There are two types of storage devices used in computers; a ‘primary storage (internal)’ device and a “Secondary Storage (external)’ device.

Internal	External
(Primary Storage)	(Secondary Storage) Backing Storage
RAM	Hard Disk
ROM	Floppy Disk
Register	CD ROM
Cache	Magnetic Tape

Features of Internal & External Storage Devices

• Internal memories are faster than external memories.
• Internal memories directly communicate with the CPU. Where as External memories must communicate to the CPU through the internal memory.
• In general internal memories are temporary (except ROM) and External memories are permanent.
• Internal memories more expensive than external memories.

Primary & Secondary Storage Devices

Primary: “A storage location that holds memory for short periods or overwritten”. For computer RAM is an example of a primary (Volatile) storage device.

Secondary: “A storage medium that holds information until it is deleted or overwritten”. For example of a secondary storage device. (Nonvolatile) 

RANDOM ACCESS MEMORY (RAM)

RANDOM ACCESS MEMORY (RAM)

      “A computer uses RAM to hold volatile (temporary) instructions and data needed for processing”.

MEMORY MODULES       

·        SIMM

·        DIMM )SD, DDR, DDR2, DDR3)

·        RIMM

SIMM (Single Inline Memory Module)

• 6-9 memory chips on the circuit board.
• The contacts on the SIMM are same on both sides.
• Using in pair & used in older pc’s.

DIMM (Dual Inline Memory module)

• DIMMs are 64bit data path.
• The contacts on the DIMM are different on both sides.
• Command addresses & control singles are buffered.

RIMM (Ram bus Inline Memory Module)

·        ECC supported.

·        Requires continuous singles.

·        Must use C-RIMMs (Continuity RIMM) to empty slots.

·        Faster

·        1600 Mb/s bandwidth.

DIMMs (Dual Inline Memory Module)

SDRAM

• Synchronous Dynamic Random Access Memory.
• Waits for clock single before responding to its control inputs.

DDR RAM

• Double Data Rate Random Access Memory.
• Doubling the speed of the memory.

DDR2 RAM

• Double Data Rate 2 Random Access Memory.
• Second generation of DDR.
• Capable of operating at greater speeds storage.
• Greater bandwidth.
• Low power consumption (1.8v) & less heat.
• Incompatible with DDR slots.

DDR3 RAM

• Double Data Rate 3 SD Random Access Memory.
• Third generation of DDR.
• Capable of operating at greater speeds storage.
• Greater bandwidth (1600Mb/s).
• Low power consumption (1.5v) & less heat (thermal design).

• Incompatible with DDR slots

RAM Technologies

Static RAM (SRAM): This RAM will maintain its data as long as power is provided to the memory chips. It does not need to be rewritten periodically. SRAM is very fast but very expensive than (DRAM). SRMA is often used as cache memory due to its speed.

Dynamic RAM (DRAM): Unlike SRAM, must be continually re-written (refreshing) in order for it to maintain its data.

This is done by placing the memory on a refresh circuit that rewrites the data several hundred times pre second. DRAM is used for most system memory (RAM) because it is cheap.

ROM CHIP

ROM CHIP

This is Read Only Memory that can only be read from but not written to. ROM is used in situations where the data must be held permanently (non volatile).

The ROM chip contains system information, like time, data, installed memory and other settings. Primarily the ROM code holds startup instructions. In fact there are several different programs inside the startup instructions.

“A piece of software that permanently built in to a piece of hardware.”

POST (Power On Self Test)

• COMS (Basic Input Output System)
• BIOS
• Boot Strap Loader (Booting).
• Manufacturer details

POST (Power On Self Test)

• This is a pre-boot sequence.
• Initial program Load (IPL) on booting.
• Main duties of the POST are handling by the BIOS.

BIOS (Basic Input/Output System)

BIOS refer to the firmware code run by an IBM PC when first powered on. The primary function of the BIOS is to identify and initiate component hardware (such as hard disk, floppy and optical disk drives). This is to prepare the machine so other software programs stored on various media can load, execute, and assume control of the PC. This process is known as booting, or booting up, which is short for bootstrapping.

When the power on….BIOS initialize,

·        The clock generator.

·        The processor and caches.

·        The chipset (memory controller and I/O controller.

·        The system memory.

·        All PIC devices.

·        The primary graphics controller.

·        Mass storage controllers (SATA and IDE controllers).

·        Various I/O controllers (such keyboard/mouse and USB).

·        Finally, it loads the boot loader for the operating system, and transfers control to it. The entire process is known as power-on self-test (POST).

ROM Types

·        Programmable ROM (PROM): This is basically a ROM chip that can be written to once. IT is much like a CD-R drive that burns data in to the CD. Some companies use special machinery to write PROMs for special purposes.

·        Erasable Programmable ROM (EPROM): This is just like PROM expects that you can erase the Rom by shining a special Ultra-Violet light in to a sensor a top the ROM chip for a certain amount of time. Doing this wipes the data out, allowing it to be rewritten.

·        Electrically Erasable and Programmable ROM (EEPROM): (Also called Flash BIOS) this Rom can be rewritten through the use of special software program. Flash BIOS also operates this way, allowing users to update their BIOS.

ROM Manufacturers: Award software, AMI (American Mega trends), Phoenix Software