Evolution of Computers Page 1The growth of the computer industry started with the need for performing fast calculations. Some early calculating devices are:Abacus: It was discovered in around 3000 BC. It consisted of beads on movable rods divided into two parts. Addition and multiplications of numbers was done by using the place value of digits of the numbers and position of beads in an abacus.Napier’s Logs and Bones: The idea of logarithm was developed by John Napier in 1617. He devised a set of numbering rods known as Napier’s bones through which both multiplication and division could be performed. Pascaline: Blaise Pascal, a French mathematician invented an adding machine in 1642 that was made up of gears. It was used for addition and subtraction of numbers.Leibnitz’s Calculator: In 1673, Gottfried, a German mathematician extended the capabilities of the adding machine invented by Pascal to perform multiplication and division.Jacquard’s Loom: Joseph Jacquard devised punch cards and used them to control loom in 1801.Difference Engine and Analytical Engine: Charles Babbage, an English mathematician developed a machine called Difference Engine. Later, he designed the Analytical Engine which used the basis of modern computer. It included the concept of central processor, memory storage and input-output devices. Even the stored information could be modified. It could perform all the four arithmetic operators. Babbage established the basic principles on which today’s modern computer work, therefore, this earned him the title of ‘Father of Modern Computers’.Mark I: In 1944 Howard Aiken developed an electromechanical machine called Mark I which could multiply two 10 digits numbers in 5 seconds.John Von Neuman: In 1945, he proposed the concept of stored program computer. According to him, the processor executes the instructions stored in the memory of the computer. Since, there is only one communication channel, the processor at a time can either fetch data or an instruction. This limitation is known as Von Neumann bottleneck.EDVAC: Electronic Discrete Variable Automatic Computer was the first stored program computer developed in 1952.ENIAC: Electronic Numerical Integrator And Calculator was the first electronic computer developed.

Generation of computersThe computer generation is categorized by the technology used.The First Generation (1942-55)Salient features of First generation computers are:

Used vacuum tubes to control and amplify electronic signals. Huge computers and occupy lot of space. High electricity consumption and high heat generation Not reliable and prone to frequent hardware failure Very costly and require frequent maintenance Require air conditioning environment Commercial production was difficult Programming was done in machine language. The Assembly language stared at the end of this

generation. Examples: ENIAC, EDVAC, UNIVAC - I

The Second Generation (1955-64)Salient features of Second generation computers are:

Used transistors Smaller in size and less expensive Consumed less electricity and emitted less heat Magnetic core memory and magnetic disk were used First operating system developed Require air conditioning environment Programming in Assembly language. The High-level language stared at the end of this generation. Wider commercial use but commercial production was difficult.

Examples: IBM - 1401, IBM 1620, UNIVAC 1108 Page 2

The Third Generation (1964-75)Salient features of Third generation computers are:

Use integrated circuits Smaller in size, faster and more reliable Low power consumption and less emission of heat Example: IBM 360 series

The Fourth Generation (1975 onwards)Salient features of Fourth generation computers are:

ICs with LSI and VLSI technology Microprocessor developed Portable computer developed Networking and data communication became popular Different types of secondary memory with high storage capacity and fast access developed. Very reliable, powerful and small size Negligible power consumption and heat generation Very less production cost

The Fifth Generation Salient features of Fifth generation computers are:

Parallel processing: Many processors are grouped together Superconductivity: To develop devices that respond to human languages and will have the ability to

apply previously gained knowledge to execute a task Artificial Intelligence : Make the decision to execute a task

Example: Voice recognition, Visual recognition etc.

Hardware Concepts

A computer is an electronic device that processes input data and produces result (output) according to a set of instructions called program. Data: It is the term used for raw facts and figures. For example, 134, 9, ‘Raju’, ‘C’ etc.Information: Data represented in useful and meaningful form is called information. For example, Raju is 9 years old is and information.

A computer performs basically five major functions irrespective of its size and make. It accepts data or instructions by way of input (Input Unit) It stores data(Memory) It processes data as required by the user (Central Processing Unit - ALU) It controls operations of a computer (Central Processing Unit - Control Unit) It gives results in the form of output (Output Unit)

Hardware is the physical tangible parts of computer

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Input Unit: It takes the input and converts it into binary form so that it is understood by the computer.

Central Processing Unit / Microprocessor It is a processor on a single chip. It is the brain of a computer. CPU consists of two parts: Control Unit (CU) and Arithmetic Logic Unit (ALU) ALU performs all arithmetic and logical operations. CU controls all other components and activities of the computer.

Memory Registers A register is a temporary unit of memory in the CPU. This receives data/information and then this data/information is held as per requirement. Each register in CPU has a specific function.

Output Unit: It re-converts the binary signal to be understood by human beings.

Communication Bus: A Bus is a subsystem that transfers data and instructions between functional components of a computer or between different computers. Buses can be Parallel Buses, which carry data words in parallel on multiple wires, and Serial Buses, which carry data in bit-serial form. Buses are of three types.1. The Address Bus carries a number called memory address that indicates the desired location of data.2. The bidirectional Data Bus, transfers data and instructions (reads or writes the data)3. A Control Bus is used to direct and monitor the actions of the other functional components of

computer.

Concept of Booting: When a computer is switched on, a copy of boot program is brought from ROM into the main memory. The process is called booting. The CPU first runs the jump instruction that transfers to BIOS (Basic Input Output System) and it starts executing. The BIOS conducts a series of self-diagnostic test called POST (Power on Self-Test). Thereafter the BIOS locate a bootable drive to load the boot sector. The execution is then transferred to the Boot Strap Loader program on the boot sector which loads and executes the operating system.

Booting process is of two types – Warm and ColdCold Booting: When the system starts from initial state i.e., it is switched on (Power button is pressed), we call it cold booting or hard booting. Warm booting: When the system restarts or reset button is pressed, we call it warm booting or soft booting. The system does not start from initial state and so all diagnostic tests need not be carried out.

Classification of ComputerThe computers can be classified based on the technology being used as: Digital, Analog and Hybrid

Main Memory(RAM and ROM)

Input Unit

E.g. Keyboard, Mouse, Light pen, Touch Screens, Graphics Tablets, Joystick, Microphone,OCR, Scanner, Smart Card reader, Barcode reader, Biometric sensor, web camera

Output Unit

E.g. Monitor/Visual Display Unit (VDU), LCD screen, Television, Printer (Dot MatrixPrinter, Desk jet/ Inkjet/ Bubble jet Printer, Laser Printer), Plotter, Speaker

Secondary StorageE.g, Hard Disk, Floppy Disk

Removable Tertiary Media : Compact Disk, Magnetic Tape, Digital Versatile Disk (DVD) USB Drive, Memory cards

Cache Memory

Central Processing Unit (CPU)

Arithmetic & Logical Unit (ALU)

Control Unit (CU)

Memory Registers

Page - 4Digital Computers: These computers are capable of processing information in discrete form i.e., 0 and 1. Analog Computers: These computers works on continuously changeable aspects of physical phenomenon such as pressure, mechanical motion and electrical quantities.Hybrid Computers: These computers use both analog and digital technology. It has the speed of analog computer and the accuracy of digital computer.

Classification of Digital ComputersMicro Computers: Also known as Personal Computers. It uses a entire CPU on single chip called microprocessor.Mini Computers: These computers can support multiple users working simultaneously on the same machine.Main Frame: These computers are large and very powerful computers with very high memory capacity. These can process huge databases such as census at extremely fast rate.Super Computers: These are fastest and very expensive computers. They can execute billions of instructions per second. These are multiprocessor, parallel systems suitable for huge amounts of mathematical calculations.

The main difference between a supercomputer and mainframe is that a supercomputer executes fewer programs as fast as possible whereas a mainframe executes many programs concurrently.

Internal Storage encoding of CharactersASCII: It stands for American Standard Code for Information Interchange. ASCII-7 represents 128 characters. ASCII – 8 represents 256 characters.ISCII: It stands for Indian Standard Code for Information Interchange. It is a 8 bit code which allow Indian script alphabets to be used.Unicode: It is a new universal coding standard adopted by all new platforms. It provides a unique number for every character irrespective of the platform, program and the language.

Microprocessor: The entire CPU on single chip.Characteristics of MicroprocessorInstruction Set: It is a set of instructions that the microprocessor executes.Word Length: The number of bits processed in a single instruction is called word length or word size. The word size is directly proportional to the processing power of CPU. The 64 bit processor is two times faster than 32 bit processor.System Clock speed: The microprocessor’s pace is controlled by the system clock. The system clock generates pulses which are measured in million of cycles per second (MHz). The number of pulses generated by the clock per unit of time is its clock speed. Each microprocessor is characterized by its clock speed.

Classification of MicroprocessorsRISC: It stands for Reduced Instruction Set Computer. It is a type of microprocessor architecture that uses a small set of instructions of uniform length.CISC: It stands for Complex Instruction Set Computer. A CISC chip such as Intel Pentium provides programmers with hundreds of Instructions of variable sizes.EPIC: It stands for Explicitly Parallel Instruction Computing. It is a computer architecture that combines the best features of RISC and CISC. For example, Intel’s 64 bit processor based on EPIC.

Memory Units: Bit (Binary Digit) / Byte (KiloByte, MegaByte, GigaByte, TeraByte, PetaByte, ExaByte, ZettaByte, YottaByte)The elementary unit of memory is a bit. A group of 4 bits is called a nibble and a group of 8 bits is called a byte. One byte is the minimum space required to store one character.

1 Byte = 8 bits1 KiloByte (KB) = 1024 Bytes1 MegaByte(MB) = 1024 x 1024 Bytes = 1024 KB

Page - 51 GigaByte(GB) = 1024 x 1024 x 1024 Bytes = 1024 MB1 TeraByte(TB) = 1024 x 1024 x 1024 x 1024 Bytes = 1024 GB1 PetaByte(PB) = 1024 x 1024 x 1024 x 1024 x 1024 Bytes = 1024 TB1 ExaByte(EB) = 1024 x 1024 x 1024 x 1024 x 1024 x 1024Bytes = 1024 PB1 ZettaByte(ZB) = 1024 x 1024 x 1024 x 1024 x 1024 x 1024 x 1024 Bytes = 1024 EB1 YottaByte(YB) = 1024 x 1024 x 1024 x 1024 x 1024 x 1024 x 1024 x 1024 Bytes = 1024 ZB

Primary and Secondary MemoryThe computer memories can be divided into following categories:

Primary Memory Secondary Memory Cache Memory

Main Memory (Primary storage or Internal Memory): It is directly accessible to the CPU. It is of two types RAM & ROM

RAM ROMRandom Access Memory is used for primary storage in computers to hold active information of data and instructions.

Read Only Memory is used to store the instructions provided by the manufacturer to check basic hardware and to load operating system from appropriate storage device.

It is a temporary memory. The data or instructions are lost when electricity goes off. It is also called as volatile memory.

It is a permanent memory. The data and instructions are retained even when electricity goes off. It is also called as non - volatile memory.

Examples: DDR1 SDRAM, DDR2 SDRAM, DDR3 SDRAM (Double data rate synchronous dynamic random access memory)

Examples: PROM  (programmable) , EPROM (erasable programmable), EEPROM (Electrically Erasable Programmable )

RAM can be classified into two categories:Dynamic RAM: The data stored is refreshed continuously and this consumes a lot of processor time.Static RAM: It is faster because it is made up of flip flops to store data and these flip flops do not require any refreshing.

ROM is available in various forms:PROM: Once it is programmed, it cannot be changed.EPROM: The content can be erased by exposing in ultraviolet light and it can be programmed.EEPROM: The content can be erased using electric signals and it can be programmed.

Cache Memory: It is a special high speed memory. it is used to hold frequently accessed data and instructions. Whenever some data is required, the CPU first looks into cache. If data is found, we call it a cache hit and the information is transferred to the CPU. In case of a miss, the main memory is accessed. There are two types of cache memory:L1 cache: It is small and is built inside the CPU. It is fast as compared to L2 cache.L2 cache: It is large but slower and is mounted on the motherboard.

Secondary Memory

Secondary Storage Devices: (External Memory) differs from primary storage in that it is not directly accessible by the CPU. The computer usually uses its input/output channels to access secondary storage and transfers the desired data in primary storage. Secondary storage does not lose the data when the device is powered down—it is non-volatile.

1. Magnetic storage  uses different patterns of magnetization on a magnetically coated surface to store information. Magnetic storage is non-volatile. The information is accessed using one or more read/write heads which may contain one or more recording transducers.

Page - 6Hard disk drive, used for secondary storageFloppy disk, used for off-line storageMagnetic tape data storage, used for tertiary and off-line storage

2. Optical storage , The information is stored and read using a laser beam. The data is stored as a spiral pattern of pits and ridges denoting binary 0 and 1. Examples are CD and DVD.Compact Disk: It stores app. 700MB of data. There are three types of CDs.CD-ROM: It stands for Compact Disk – Read Only Memory and data is written on these disks at the time of manufacture. This data cannot be changed but only read.CD-R: It stands for Compact Disk- Recordable. Data can be recorded but only once. After that data cannot be modified or erased.CD-RW: It stands for Compact Disk – Rewritable. It can be read or written multiple times.DVD: It stands for Digital Versatile Disk or Digital Video Disk. It stores 4.7GB of data It comes in three variations:DVD-ROM, DVD – R, DVD – RW

Blu-Ray Disk: It stores up to 25GB of data. The CDs and DVDs use red laser beam whereas blue ray disk uses a blue laser to read/write data on a disk.

3. Solid State Memories: The term solid state means no moving parts. It based on electronic circuits with no moving parts.Pen Drive or Flash Drive can be repeatedly erased and written using electric signals. A flash drive consists of a small printed circuit board carrying the circuit elements and a USB connector, insulated electrically and protected inside a plastic, metal, or rubberized case which can be carried in a pocket or on a key chain, Most USB flash drives draw their power from the USB connection, and do not require a battery.

Input / Output Ports and Connections: Communication Ports (Input / Output Ports): Used to connect various peripherals (devices) to the computer

1. Serial Port: It transfers data serially 1 bit at a time. It comes in the form of 9 pin or 25 pins male connector. It is used to connect devices like mouse and modem.

2. Parallel Port: It can send or receive a byte (8 bits) at a time. The 8 bits are transferred parallel to each other. It comes in the form of 25 pin female connector. It is used to connect devices like printer, scanner, and external hard disk CD writer, zip drive, tape backup drive, etc.

3. USB (Universal Serial Bus) : It is intended to replace many varieties of serial and parallel ports. It is used to connect to various devices like printers, scanners, mice, joystick, digital camera, web cameras, speakers, telephones, zip drives, network connections, scientific data acquisition devices, etc.

4. PS-2 Port (Personal System-2): It is used to connect keyboard (purple coloured port) or mouse (green coloured port).

5. Bluetooth: Bluetooth is an open wireless technology standard for exchanging data over short distances creating personal area networks (PANs) with high levels of security. Bluetooth is a standard for a small, cheap radio chip to be plugged into computers, printers, mobile phones, etc

6. Infrared Port: The data is transmitted through infrared. The remote control of TV set uses the same technology.

7. Firewire Port: This port is used to transfer data rapidly from one electronic device to another. It has the ability to interact with a number of different devices since it

provides a single plug and socket connection for all devices. The data transfer is faster than USB port.