Computer Abbreviations PDF

1 www.jkchrome.com www.jkchrome.com www.jkchrome.com Computer Abbreviations For All Competitive Exams 1. AI – Artificial intelligence m 2....

1 www.jkchrome.com www.jkchrome.com www.jkchrome.com Computer Abbreviations For All Competitive Exams 1. AI – Artificial intelligence m 2. ALGOL – Algorithmic Language co 3. ARP – Address resolution Protocol 4. ASP- Active Server Pages e. 5. ASCII – American Standard Code for Information Interchange 6. AMR - Adaptive Multi-Rate Codec 7. 8. AAC - Advanced Audio Coding m ATA – Advanced Technology Attachment ABR – Average Bit rate ro 9. AMOLED – Active-Matrix Organic Light-Emitting Diode ch 10. AMD – Advanced Micro Devices 11. AVI – Audio Video Interleaved.jk 12. ATM – Asynchronous Transfer Mode 13. ANSI - American National Standard Institute w 14. ARPANET- Advanced Research Projects Agency Network 15. ADSL -Asymmetric Digital Subscriber Line w 16. API -Application Program Interface w 17. ACID- Atomicity Consistency Isolation Durability 18. BINAC - Binary Automatic Computer 19. BCC – Blind Carbon Copy 20. BASIC - Beginner’s All-purpose Symbolic Instruction Code 21. BIOS – Basic Input Output System Page 1 Follow us: Official Site, Telegram, Facebook, Instagram, Instamojo 2 www.jkchrome.com www.jkchrome.com www.jkchrome.com 22. BCD - Binary Coded Decimal 23. BHTML - Broadcast Hyper Text Markup Language 24. BIU - Bus Interface Unit m 25. BMP – Bitmap 26. BPS - Bytes Per Second co 27. BBP – Base band Processor 28. BPM – Business Process Modeling e. 29. BGP - Border Gateway Protocol 30. 31. BIPS - Billion Instruction Per Second BCR - Bar Code Reader m ro 32. BRD - Blu Ray Disc 33. CAD - Computer Aided Design ch 34. CC – Carbon Copy 35. COBOL – Common Business Oriented Language.jk 36. CD – Compact Disc 37. CRT – Cathode Ray Tube w 38. CD-R – Compact Disc Recordable w 39. CDROM – Compact Disc Read Only Memory w 40. CDRW – Compact Disc Rewritable 41. CSS – Cascading Style Sheets 42. CISC- Complex Instructions Set Computers 43. CUI - Character User Interface 44. CDMA- Code Division Multiple Access Page 2 Follow us: Official Site, Telegram, Facebook, Instagram, Instamojo 3 www.jkchrome.com www.jkchrome.com www.jkchrome.com 45. COMPUTER- Common Operating Machine Purposely Used for Technological and Educational Research. 46. CAN - Campus Area Network m 47. CNM- Circulatory Network Mode 48. DBA – Data Base Administrator co 49. DBMS – Data Base Management System 50. DNS – Domain Name System e. 51. DPI – Dots Per Inch 52. DRAM – Dynamic Random Access Memory 53. m DVD – Digital Video Disc/Digital Versatile Disc ro 54. DVDR – Digital Versatile Disc Recordable 55. DVDROM – DVD Read Only Memory ch 56. DVDRW – DVD Rewritable 57. DVR – Digital Video Recorder.jk 58. DOS – Disk Operating System 59. DHCP - Dynamic Host Configuration Protocol w 60. DSL- Digital Subscriber Line w 61. DHTML Dynamic Hyper Text Markup Language 62. EBCDIC – Extended Binary Coded Decimal Interchange Code w 63. e-Commerce – Electronic Commerce 64. EDP – Electronic Data Processing 65. EEPROM – Electrically Erasable Programmable Read Only Memory 66. e-Mail – Electronic Mail 67. ENIAC - Electronic Numerical Integrator and Computer Page 3 Follow us: Official Site, Telegram, Facebook, Instagram, Instamojo 4 www.jkchrome.com www.jkchrome.com www.jkchrome.com 68. EOF - End Of File 69. EPROM - Erasable Programmable Read Only Memory 70. EDI - Electronic Data Interchange m 71. FAX - Far Away Xerox/ facsimile 72. FDC - Floppy Disk Controller co 73. FDD - Floppy Disk Drive 74. FORTRAN - Formula Translation e. 75. FS - File System 76. 77. FTP - File Transfer Protocol FIFO - First In First Out m ro 78. FAT - File Allocation Table 79. GPRS - General Packet Radio Service ch 80. GPS - Global Positioning System 81. GUI - Graphical User Interface.jk 82. Gb - Gigabit 83. GB - Gigabyte w 84. GIF - Graphics Interchange Format w 85. GSM - Global System for Mobile Communication w 86. GIGO - Garbage in Garbage Out 87. HDD - Hard Disk Drive 88. HP - Hewlett Packard 89. HTML - Hyper Text Markup Language 90. HTTP - Hyper Text Transfer Protocol 91. HTTPS - Hyper Text Transfer Protocol Secure Page 4 Follow us: Official Site, Telegram, Facebook, Instagram, Instamojo 5 www.jkchrome.com www.jkchrome.com www.jkchrome.com 92. HDMI - High Definition Multimedia Interface 93. HDTV - High Definition Television 94. HVD- Holographic Versatile Disc m 95. INTEL - Integrated Electronics 96. IP - Internet Protocol. co 97. IC- Integrated Circuit 98. ISP - Internet Service Provider. e. 99. IMAP- Internet Message Access Protocol 100. 101. IVR- Interactive Voice Response m ICANN - Internet Corporation of Assign Names & Numbers ro 102. ISDN - Integrated Servers Digital Network 103. JAD - Java Application Descriptor ch 104. JPEG - Joint Photographic Expert Group 105. Kb - Kilobit.jk 106. KB - Kilobyte 107. KHz - Kilohertz w 108. Kbps - Kilobit Per Second w 109. LED - Light Emitting Diode w 110. LCD – Liquid Crystal Display 111. LIFO- Last In First Out 112. Mb – Megabit 113. MB – Megabyte 114. MPEG – Moving Picture Experts Group 115. MMS – Multimedia Message Service Page 5 Follow us: Official Site, Telegram, Facebook, Instagram, Instamojo 6 www.jkchrome.com www.jkchrome.com www.jkchrome.com 116. MICR – Magnetic Ink Character reader 117. MIPS – Million Instructions Per Second 118. MIME - Multipurpose Internet Mail Extension m 119. MIDI - Musical Instrument Digital Interface 120. MANET - Mobile Ad-Hoc Network co 121. Mbps- megabits per second 122. MAC- Media Access Control e. 123. MODEM- Modulator Demodulator 124. 125. NAT - Network Address Translation NIC – Network Interface Card m ro 126. NOS – Network Operating System 127. NTP - Network Time Protocol ch 128. OMR – Optical Mark Reader 129. OOP – Object Oriented Programming.jk 130. OSS – Open Source Software 131. OS- Operating System w 132. OCR -Optical Character Reader / Recognition w 133. P2P - Peer-to-peer w 134. PDA - Personal digital assistant. 135. PDF - Portable Document Format 136. PNG - Portable Network Graphics 137. POS – Point Of Sale 138. PPP – Point-to-Point Protocol 139. PROM – Programmable Read Only Memory Page 6 Follow us: Official Site, Telegram, Facebook, Instagram, Instamojo 7 www.jkchrome.com www.jkchrome.com www.jkchrome.com 140. PSTN – Public Switched Telephone Network 141. PING – Packet Internet Gopher 142. PAN- Personal Area Network m 143. PCB -Printer Circuit Board 144. PCB - Printer Circuit Board co 145. PHP- Hypertext Preprocessor 146. RAM – Random Access Memory e. 147. ROM -Read Only Memory 148. 149. m RDBMS – Relational Data Base Management System RIP – Routing Information Protocol ro 150. RTF – Rich Text Format 151. RARP - Reverse Address Resolution Protocol ch 152. SMTP – Simple Mail Transfer Protocol 153. SQL – Structured Query Language.jk 154. SRAM – Static Random Access Memory 155. SNMP – Simple Network Management Protocol w 156. SIM – Subscriber Identification Module w 157. SMPS - Switch Mode Power Supply w 158. SFTP Secure File Transfer Protocol 159. SSH - Secure Shell 160. SIP - Session Initiation Protocol 161. SAN -Storage Area Network 162. TCP – Transmission Control Protocol 163. TB – Tera Bytes Page 7 Follow us: Official Site, Telegram, Facebook, Instagram, Instamojo 8 www.jkchrome.com www.jkchrome.com www.jkchrome.com 164. TFTP --Trivial File Transfer Protocol 165. Tel Net - Telecommunication Networking 166. TIPS -Trillion Instruction Per Second m 167. UPS – Uninterrupted Power Supply 168. URI – Uniform Resource Identifier co 169. URL – Uniform Resource Locator 170. USB - Universal Serial Bus e. 171. ULSI - Ultra Large Scale Integration 172. 173. UNIVAC - Universal Automatic Computer m UMTS - Universal Mobile Telecommunication System. ro 174. UDP -User Datagram Protocol 175. VIRUS - Vital Information Resource Under Seized ch 176. VOIP - Voice Over Internet Protocol 177. VAR – Variable.jk 178. VGA – Video Graphics Array 179. VSNL – Videsh Sanchar Nigam Limited w 180. VDU – Visual Display Unit w 181. VAN - Value Added Network w 182. VIRUS- Vital Information Resource Under Siege 183. WAIS - Wide-Area Information Server. 184. Wi-Fi – Wireless Fidelity 185. WLAN – Wireless Local Area Network 186. WPA – Wi-Fi Protected Access 187. WWW – World Wide Web Page 8 Follow us: Official Site, Telegram, Facebook, Instagram, Instamojo 9 www.jkchrome.com www.jkchrome.com www.jkchrome.com 188. WORM – Write Once Read Many 189. WBMP - Wireless Bitmap Image 190. WMA - Windows Media Audio m 191. WMV - Windows Media Video 192. WIMAX- Worldwide Interoperability for Microwave Access co 193. XHTML – eXtensible Hypertext Markup Language 194. XML - eXtensible Markup language e. 195. ZB – ZettaByte m ro ch.jk w w w Page 9 Follow us: Official Site, Telegram, Facebook, Instagram, Instamojo 10 www.jkchrome.com www.jkchrome.com www.jkchrome.com m co e. m ro ch.jk w w w 11 www.jkchrome.com www.jkchrome.com www.jkchrome.com was on. He wanted a character that would not, under any conceivable circumstances, be found in the user’s name. He looked down at the keyboard and chose the @ sign among various punctuation marks available on his Model 33 teletype keyboard, without an idea that he was creating an icon for the internet world. A general format for an e-mail address is: username@computer_name. The part before the @ sign is the local part of the address, the user name of the recipient, and the part after the @ sign is the domain part which is a host computer name. The `@’ symbol indicates that the user can be reached on the Internet by giving the email address(also called the User’s Uniform Resource Locator (URL)). m  In 1973, the Transmission Control Protocol/Internet Protocol (TCP/IP) was designed and in 1983 it became the standard for communicating between computers over the Internet. In 1976, US Presidential candidate Jimmy Carter and running mate Walter Mondale used email to plan campaign events. In the same year, Queen Elizabeth sent her first email, co becoming the first state leader to do so. In 1982, the term “Internet” was used for the first time. Files on Internet e. The internet is a collection of a large number of client-server based systems. So all files and other resources on it are stored on secondary storage devices of the respective servers. Servers of m websites are termed as web servers. When we type in a URL of a website in the address bar of browser, it makes a connection to that web server which in turn fetches the data from the secondary storage device (such as the hard disk) that they must be using and returns it to the respective browser. The same holds true for any other resource (image, MP3 file, zipped file, etc.) ro that you access on the internet. Common methods of Internet access in homes include dial-up, landline broadband (over coaxial ch cable, fiber optic or copper wires), Wi-Fi, satellite and 3G/4G technology cell phones. Public places to use the Internet include libraries and Internet cafes, where computers with Internet connections are available. There are also Internet access points in many public places such as airport halls and coffee shops, in some cases just for brief use while standing. Various terms are used, such as “public Internet.jk kiosk”, “public access terminal”, and “Web payphone”. Many hotels now also have public terminals, though these are usually fee-based. These terminals are widely accessed for various usage like ticket booking, bank deposit, online payment etc. Wi-Fi provides wireless access to computer networks, and therefore can do so to the Internet itself. (wiki) w Buffering in internet w Buffering is a situation which occurs when a streaming media player is saving portions of a streaming media file to local storage for playback. Most streaming media players buffer a small percentage of a streaming media presentation before beginning to play it. Buffering also may w occur in the middle of a presentation when available bandwidth does not match the presentation’s required bandwidth. How do search engines work? A search engine does not search the entire Internet, but databases of Web pages. When a designer contacts a search engine for the addition of his website in the database, a program called Spider visits the site, reads the pages, indexes the contents and follows links to move on. Search engines like Google use algorithms to find pages with matter relevant to the keywords entered by the user. 12 www.jkchrome.com www.jkchrome.com www.jkchrome.com If the title or headings of the page contain the keywords, then it gets higher preference. Google also uses a patented algorithm called PageRank system that ranks a website based on how many sites have links to it and their ranks as well. Basic Components of Networks A network has 5 basic components viz. clients, servers, channels, interface devices and operating systems. A brief intro: m 1. Servers: Servers or Host computers are are powerful computers that store data or applications and connect to resources that are shared by the users of a network. 2. Clients: Client is the computer used by the users of the network to access the servers and co shared resources (such as hard disks and printers). So, a personal computer is a client. 3. Channels: The technical name of channels is network circuit. It is the pathway over which information travels between the different computers (clients and servers) that comprise the network. 4. Interface devices: The devices that connect clients and servers (and sometimes other e. networks) to the channel are called interface devices. The common examples are modems and network interface cards. 5. Operating systems: This is the Network Software. It serves purpose that the operating m system serves in a stand-alone computer. Channel Dimensions ro There are a number of varieties of the types, speeds and capabilities of network channels. These may be Transmission medium such as wireless or wire line, Transmission rate or bandwidth, Transmission directional capability and the Type of the Signal. ch  Transmission medium is the physical medium of the channel, which can be either wire line or wireless. The wire line is called the guided media or line based media. The wire line are of several kinds such as twisted pair wire, coaxial cable and fiber optic cable. The.jk wireless media there is no physical wire along which information travels and the information is transmitted without wires from one transmission station to the next. Common examples are radio, mobile networks, microwave and satellite.  Transmission rate or bandwidth shows how fast information can be transmitted over w the channel. It is measured in bits per second (bps).  Transmission directional capability refers to the direction in which information can be transmitted over a channel; It can be simplex, half-duplex or full-duplex. Simplex means w that information can be transmitted only in one direction, Half-duplex means that information can be transmitted in both directions, but only in one direction at a time. Full- duplex means that Information can be transmitted in both directions simultaneously. w  Signal type can be analog and digital. Analog signals are ‘continuous’ (they take on a wide range of values) and digital signals are ‘discrete’, and binary (take on only two values). So, Digital signals are more suitable for computer networks because, computers represent all information in binary. Network Protocols A protocol is more like a language that can be shared by many people. If all the people would like to use the same language, the protocol becomes a standard. The same is applicable with networks. 13 www.jkchrome.com www.jkchrome.com www.jkchrome.com Most networks have one feature in common that they transmit information by breaking the original information into a set of messages (called packets), transmitting these packets sequentially, and then reassembling these packets back into the original information. Each packet is a string of bits. But these packets sometimes have to travel a long way, over a bunch of different networks, there are typically lots of computers sending and receiving information over the same network, and the information getting sent can often get altered during transmission (this is called a transmission error). In order to make sure that the original information gets transmitted correctly, to the right place, computer networks use a set of rules, called networking protocols. m Thus, a data communication protocol is a set of rules that must be followed for two electronic devices to communicate with each other. These rules cover: co  Syntax: Data format and coding  Semantics: Control information and error handling  Timing: Special matching and sequence The tasks which a protocol does fall into two categories e. 1. Network layer tasks 2. Data-link layer tasks m The rules associated with each category are called network layer protocols and data-link layer protocols. Network-layer protocols ro Network-layer protocols are also known as Layer-3 protocols. These rules specify how a network does the following three tasks: ch 1. Packetizing: breaking up the information into packets, and reassembling the packets at the receiving end. 2. Addressing: Determining which computer and network the packets are headed to. 3. Routing: Determining the best way for the packets to get to where they are headed..jk The most common example of Network-layer Protocol is TCP/IP. Data-link layer protocols w The Data-link layer protocols are also known as Layer-2 protocols. These rules specify how a network does the following three tasks: w 1. Delineation: Figuring out when a message (packet) begins and ends. 2. Error control: Figuring out when a transmission error has occurred, and correcting it. w 3. Channel access: Controlling when a particular client or server accesses the channel. Ethernet is the most common example of Layer-2 protocol. The token ring protocol, developed by IBM is another example. The networks that we connect to from home using a telephone line typically use one of two data link protocols: SLIP or PPP. Routers , Bridges & Backbone 14 www.jkchrome.com www.jkchrome.com www.jkchrome.com The facilities on most LANs are very powerful. Most organizations do not wish to have small isolated islands of computing facilities confined to the buildings. They want to extend facilities over a wider area so that groups can work without having to be located together. Two or more LANs can be connected with specialized devices called Routers and bridges. Bridge connects LANs of the same type but, router is a more intelligent component that can interconnect many different types of computer network. Then, we can have Backbone Networks, which are high-bandwidth channels that typically connect LANs with each other, and are often referred to as backbones. LAN, WAN & MANs Local Area Networks (LANs) is confined to a fairly small geographic area. The clients and servers m on a LAN are connected to the same channel, and are typically in the same building or in neighboring buildings. The Metropolitan Area Networks (MANs) spans a wider area than LAN and Wide Area Networks (WANs) spread over a large geographic area, such as a country or a state. co How does a firewall work? In computer security, a firewall is a device that blocks unauthorized access to an organization’s local area network. A firewall can reside on the administrative computer, the server that acts as e. the LAN’s gateway to the Internet. The firewall keeps track of every file entering or leaving the local area network in order to detect the source of viruses and other problems that might enter the network. Development History of Ethernet m ro A network consists of multiple computers connected using some type of interface, each having one or more interface devices. The primitive computers were the self contained devices in which the data was confined in it. The only way to transfer the data from one machine to another was to take the data in a storage device and send it across the machine. So, this necessity led to invention and ch development in the networks. In a computer network, the autonomous computers are interconnected and are able to communicate with each other. Networks enable the sharing of data among groups of computers and their users..jk  Computer Networking began at the same time as computers themselves. In 1940 George Stibitz and Samuel Williams, at AT&T’s Bell Laboratories, developed their Complex Number Generator, one of the earliest digital computers and then, they made it possible for users to operate the computer remotely from teletype machines on three different w floors in their Manhattan building. They also developed a system to allow users to communicate with the machine even more remotely, via telex machines. This was the beginning of the Networking era. w  In 1964, Drs John Kemeny and Tom Kurtz of Dartmouth College in New Hampshire developed not only the simplified BASIC programming language (Beginners All-purpose Symbolic Instruction Code) but also a system called time sharing, which allowed many w students to use a single computer at what seemed like the same time, from a large number of teleprinter terminals spread around the campus and elsewhere.  However, networking is said to have started in 1976, when researchers Dr Robert Metcalfe and Dr David Boggs of the Xerox Palo Alto Research Center (PARC) presented details of a Local Computer Networking System which allowed data to be transferred between a number of computers and printers, at 2.94Mb/s (megabits per second), which was considered to be a very high speed. They dubbed the new networking system Ethernet. 15 www.jkchrome.com www.jkchrome.com www.jkchrome.com  Xerox Corporation was granted a patent for Ethernet in 1977. Then in 1979 Xerox teamed up with Digital Equipment Corporation and Intel to define the first official standard specification for Ethernet. This Ethernet Version 1.0 was capable of transferring data at 10Mb/s over fairly thick (10mm diameter) 50W coaxial cable. It was called Thick Ethernet’ or ’10Base5′. The meaning of 10Base5 is that it allowed a 10Mb/s data rate, it used baseband transmission rather than a modulated high-frequency carrier, and would give reliable data communication over cable lengths up to 500 meters.  A few years later, the 802.3 working group of the IEEE (Institution of Electrical and Electronics Engineers) released its first industry standard for Ethernet, giving it the name IEEE 802.3 Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specifications. This was the refined version of DEC-Intel-Xerox m Thick Ethernet.  In 1985, the IEEE working group came out with ‘thin’ Ethernet, also known as ‘cheapernet’ or 10Base2′. This specified the use of thinner (5mm diameter) 50W coaxial cable, which still allowed 10 Mb/s baseband transmissions as before, but with a maximum co cable length of 185 meters.  It was followed by IEEE 802.3i or 10BaseT’Ethernet standard, released in 1990. 10BaseT opened the door to much cheaper networking because it allowed 10 Mb/s transmissions over the low cost 100W unshielded twisted-pair or ‘UTP’ Category 3 cabling which had by e. then become widely used for telephone wiring in buildings.  In 1995 IEEE working group released the 802.3u standard. This became known as ‘100BaseT’ or ‘Fast Ethernet, which had 10 times the speed of 10BaseT.  In 1997 came IEEE 802.3x, which defined full duplex or simultaneous two-way data  m communication over either 10BaseT or 100BaseT. Before this development, Ethernet allowed only half duplex or ‘one way at a time’ communication. In 1998 and 1999, the IEEE working group released four different implementations of the ro 802.3z ‘Gigabit Ethernet’ standard, achieving 1Gb/s transmission or another 10-times increase in data transfer rates.  Please note that out of above, 10BaseT and 100BaseT, turn out to be very suitable and cost-effective for both home and small office networking and are widely used today. ch What is Linux Operating system? Linux is an open source operating system developed by Linus Torvalds as a version of UNIX that.jk could run on a home computer. Linux is considered to be a faster, safer operating system. He patented Linux in 1991, and then made the system and its code available to others, free of charge, over the Internet. He licensed the system in such a way that anyone can copy and use it, but any improved versions a user creates must be made available to others under the same term, so this w was under the GNU GPL. This was more than enough to make the computer programmers from all over the world to flock and make additions and advance. w Most popular Open Source Programmes are as follows: Application software w  Open Office- Office Suite  Blender — 3D graphics editor  GIMP — graphics editor  7-Zip — file archiver  Libre Office — office suite  Mozilla Thunderbird — e-mail client  Mozilla Firefox — web browser 16 www.jkchrome.com www.jkchrome.com www.jkchrome.com  Google Chrome — web browser Type of Linux Operating systems  FreeBSD — operating system derived from Unix  Haiku — free and open source operating system.  Linux/GNU — family of Unix-like operating systems  OpenSolaris — Sun Microsystems’s discontinued operating system derived from Unix  Symbian — real-time mobile operating system  Ubuntu is a popular open-source computer operating system, and a form of Linux. m Programming languages use in linux Operating system  Python — general purpose programming language co  PHP — scripting language suited for the websites Server software Use In Linux Operating System e.  WordPress — blog software  MediaWiki — wiki server software, the software that runs Wikipedia  Joomla – a website software  MongoDB — document-oriented, non-relational database    Drupal — content management system m Moodle — course management system or virtual learning environment RenovatioCMS — content management system ro  Apache — HTTP web server Open Source Software ch The DOS and Windows are the proprietary software of Microsoft. Then, we have thousands of Open source software (OSS). The OSS has its underlying’sourcecode’ made available under a license, so that the developers and users are allowed to adapt and improve it. Most popular licensing system is GNU General Public License (GNU GPl, or GPL). Under GNU GPL, the licensees.jk may not ‘close’ versions. The licensee may modify copy and redistribute anyderivative version, under the same GPl license. The licensee can either charge a fee for this service or work free of charge. Please note that Open source doesn’t just mean access to the source code. The distribution terms of open-source software must comply with the following criteria: w 1. Free Redistribution: No restriction on any party from selling or giving away the software as a component of an aggregate software distribution containing programs from several w different sources. 2. Source Code: The program must include source code, and must allow distribution in source code as well as compiled form. w 3. Derived Works: The license must allow modifications and derived works, and must allow them to be distributed under the same terms as the license of the original software. 4. Integrity of The Author’s Source Code: The license may restrict source-code from being distributed in modified form only if the license allows the distribution of “patch files” with the source code for the purpose of modifying the program at build time. The license must explicitly permit distribution of software built from modified source code. The license may require derived works to carry a different name or version number from the original software. 17 www.jkchrome.com www.jkchrome.com www.jkchrome.com 5. No Discrimination Against Persons or Groups: The license must not discriminate against any person or group of persons. 6. No Discrimination Against Fields of Endeavor: The license must not restrict anyone from making use of the program in a specific field of endeavor. For example, it may not restrict the program from being used in a business, or from being used for genetic research. 7. Distribution of License: The rights attached to the program must apply to all to whom the program is redistributed without the need for execution of an additional license by those parties. 8. License Must Not Be Specific to a Product: The rights attached to the program must not depend on the program’s being part of a particular software distribution. 9. License Must Not Restrict Other Software: The license must not place restrictions on other m software that is distributed along with the licensed software. 10. License Must Be Technology-Neutral: No provision of the license may be predicated on any individual technology or style of interface. co DOS and WINDOWS DOS stands for disk operating system. The most prevalent from of DOS was manufactured by Microsoft. The last version of DOS to be marketed separately was 6.22 and was used in e. conjunction with windows 3.11 windows 95 includes DOS. The main difference between windows and DOS is the ability to “multitask” or use two or more programs or data files simultaneously. In these programmes we have directories or folders that work like a filling cabinet. They help keep m our hard disk organized by keeping system files together or program files together and separate from data files. Some types of files include executable or from data files. Some types of files include executable or program files (file names end in.exe) dynamic link libraries (.dll) which are called upon by programs to do routines, and initialization files (.ini) which are used by certain ro programs to store startup settings. The earliest avtar of Microsoft Windows was Interface Manager, which was being developed in ch September 1981. The first ever version of Windows operating system was announced on November 10, 1983. It was an extension of MS DOS, and sported a graphic user interface. Windows 1.0 was finally released into market in November, 1985. Software.jk The computer programme which contains the instructions to make the hardware work are called software. There are two primary software categories viz. Operating Systems or System Software and Application Software. w Operating System handles the essential task such as maintaining file system and coordination of w data and memory with CPU, external devices and output devices. Operating System is needed to give a platform for the applications to run. Thus, we can say that Operating Systems would control the execution of instructions in the CPU of the computer, but it is the applications that perform w specific tasks of interest to end users. For example Windows is an operating system and Microsoft Word is an application. Then we have network software, which enable groups of computers to communicate, and language software which provides programmers with the tools they need to write programs. They are neither system nor application software but have the elements of both of them. Then we have Proprietary software, sharewares and freeware. The Proprietary software is the so-called packaged software which are developed and sold primarily online or offline via computer shops. The freeware and public-domain software are made available without cost. The sharewares are 18 www.jkchrome.com www.jkchrome.com www.jkchrome.com also freeware but carries a small fee for those who wish to use it. Shareware may be proprietary software that is provided to users without payment on a trial basis and is often limited by any combination of functionality, availability, or convenience. What are Beta testing and Alpha testing? Software testing is to test a software or software code to find bugs and errors. There are basically of two types: alpha testing and beta testing. The first is done at the developer end, while the second is at the user end. A beta tester is the customer itself and notes down defects and reports them to the developer. The user/ customer is called a ‘beta tester’ because he is the second one to carry out the testing. The term is derived from the fact that beta comes after alpha in the Greek m alphabet. World’s First Software co Ada Lovelace wrote a rudimentary programme for the analytical machine designed by Charles Babbage in 1827, but the machine never became operational. In 1949, the language short code appeared. It was the first computer language for electronic devices and required the programmer to change its statements into 0s and 1s by hand. e. Working of Touchscreen Monitors m In Touchscreen Monitors, we can use our finger on the computer screen to navigate through the contents. This type of screens is most commonly visible in Public Information Kiosks and ATMs. The touch screen has 3 main components as follows: ro  A Touch sensor: It’s a textured coating across the glass face. This coating is sensitive to pressure and registers the location of the user’s finger when it touches the screen.  A controller: It is a small PC card that connects the touch sensor to the PC. It takes ch information from the touch sensor and translates it into information that PC can understand.  A Software driver: Software Driver is a software update for the PC system that allows the touchscreen and computer to work together. It tells the computer’s operating system how.jk to interpret the touch event information that is sent from the controller. Please note that the touch screen monitor is an input device and it needs to be combined with a display and a PC to make a complete touch input system. w There are 3 basic systems used to recognize a person’s touch. w 1. Resistive : The resistive system consists of a normal glass panel that is covered with a conductive and a resistive metallic layer. These layers are held apart by spacers, and a scratch-resistant layer is placed on top of the whole set up. An electrical current runs w through the two layers while the monitor is operational. When a user touches the screen, the two layers make contact in that spot. The change in electrical field is noted and coordinates of the point of contact are calculated. Once the coordinates are known, a special driver translates the touch into something that the operating system can understand, much as a computer mouse driver translates a mouse’s movements into a click or drag. 2. Capacitive: In the capacitive system, a layer that stores electrical charge is placed on the glass panel of the monitor. When a user touches the monitor with his or her finger, some of the charge is transferred to the user, so the charge on the capacitive layer decreases. 19 www.jkchrome.com www.jkchrome.com www.jkchrome.com This decrease is measured in circuits located at each corner of the monitor. The computer calculates, from the relative differences in charge at each corner, exactly where the touch event took place and then relays that information to the touch screen driver software. One advantage of the capacitive system is that it transmits almost 90 per cent of the light from the monitor, whereas the resistive system only transmits about 75 per cent. This gives the capacitive system a much clearer picture than the resistive system. 3. Surface acoustic wave: The surface acoustic wave system uses two transducers (one receiving and one sending) placed along the x and y axes of the monitor’s glass plate. Also placed on the glass are reflectors — they reflect an electrical signal sent from one transducer to the other. The receiving transducer is able to tell if the wave has been disturbed by a touch event at any instant, and can locate it accordingly. The wave setup m has no metallic layers on the screen, allowing for 100-percent light throughput and perfect image clarity. This makes the surface acoustic wave system best for displaying detailed graphics (both other systems have significant degradation in clarity). co Another area in which the systems differ is which stimuli will register as a touch event. A resistive system registers a touch as long as the two layers make contact, which means that it doesn’t matter if you touch it with your finger or a rubber ball. A capacitive system, on the other hand, must have a conductive input, usually your finger, in order to register a touch. The surface e. acoustic wave system works much like the resistive system, allowing a touch with almost any object — except hard and small objects like a pen tip. Types of Computer Monitors Monitor m Monitor or visual display unit is the most common output device of a computer. It comprises a ro display device, circuitry, and an enclosure. The display device in modern monitors is typically a thin film transistor liquid crystal display (TFT-LCD) thin panel, while older monitors use a cathode ray tube about as deep as the screen size. The primitive monitors used the Cathode Ray ch Tubes (CRTs), until they were replaced by LCD monitors. A cable connects the monitor to a video adapter (video card) that is installed in an expansion slot on the computer’s motherboard. This system converts signals into text and pictures and displays them on Monitor. The computer sends a single to the video adapter, telling it what character,.jk image, or graphic to display. The video adapter converts that signal to a set of instructions that tell the display device (monitor) how to the image on the screen. We need to understand separte concepts to understand how a Monitor works: w Cathode Ray Tube w Cathode Ray Tube (CRT) was invented by German physicist Karl Ferdinand Braun in 1897. It is the device that was long used in most computer displays, video monitors, televisions radar w displays and oscilloscopes. The CRT has undergone numerous development until the advent of plasma screens, LCD , TVs, DLP, OLED displays, and other technologies. Technically, CRT has an electronic vacuum tube employing a focused beam of electrons. Pixels That most common type of graphics monitors employing a cathode ray tube are the raster-scan display based on television technology. In such a system, the Electron beam is swept across the screen, one row at a time from top to bottom. As this beam moves across each row, the beam intensity is turned on and off. This would create a pattern of illuminated spots. 20 www.jkchrome.com www.jkchrome.com www.jkchrome.com There is a memory area called refresh buffer or frame buffer where the picture definition is stored. This memory area holds the set of intensity values for all the screen points. These stored intensity values are then retrieved from the refresh buffer and “painted” on the screen one row (scan line) at a time. Such each screen point is referred to as a ‘pixel’ or pel (shortened forms of picture elements). The capability of a raster-scan system to store intensity information for each pixel makes it well suited for the realistic display of scenes containing subtle shading and colour patterns. LCD TFT Display m Liquid Crystal Display television (LCD TV) is television that uses LCD technology for its visual output. The technology used is generally TFT. TFT refers to a Thin Film Transistor, which is a special kind of field effect transistor made by depositing thin films for the metallic contacts, semiconductor active layer, and dielectric layer. The channel region of a TFT is a thin film that is co deposited onto a substrate (often glass, since the primary application of TFT is in liquid crystal displays). LCD panels are made of two layers of transparent material, which are polarized, and are “glued” e. together. One of the layers is coated with a special polymer that holds the individual liquid crystals. Current is then passed through individual crystals, which allow the crystals to pass or block light to create images. LCD crystals do not produce their own light, so an external light m source, such as florescent bulb is needed for the image created by the LCD to become visible to the viewer. Thus, LCDs use a strong backlight as the light source and control how much of this light is allowed to reach the pixels by selectively allowing the light to reach each pixel. LCDs achieve this by taking advantage of a key property of ‘twisted’ liquid crystal molecules, which have ro the ability to naturally block polarized light but then let it through by degrees when a small electric field is applied. LCD cells are accurately controlled and arranged in a flat matrix of rows and columns. ch Plasma Display Panel We have read above that LCD crystals do not produce their own light, so an external light source,.jk such as florescent bulb is needed for the image created by the LCD to become visible to the viewer. The Plasma television technology is absolutely different from this. The Plasma Display Panel is based loosely on the fluorescent light bulb. The display itself consists of very microscopic cells and within each cell two glass panels are separated by a narrow gap in which neon-xenon gas is injected and sealed in plasma form. Gas is electrically charged at specific intervals and then strikes w red, green, and blue phosphors, thus creating a television image. Each group of red, green, and blue phosphors is called a pixel (picture element). w Due to presence of its own source of light, PDP suffers from the issues such as heat generation and screen-burn of static images. w Why are screensavers used in computers? Screensavers are designed to prevent phosphor burn-in on CRT and plasma computer monitors by blanking the screen or filling it with moving images or patterns when the computer is not in use are programs that display images when the computer is idle for a specified time. In early CRT monitors when the same image would be displayed for a long time, the phosphors used to make the pixels in the display glow at a constant rate for so long a period that they would discolor the glass surface of the CRT. 21 www.jkchrome.com www.jkchrome.com www.jkchrome.com But now, the advances in display technology and energy-saver monitors have solved this problem. So now we use screensavers for entertainment or security and they are perceived as works of art and used to prevent others from viewing confidential data when the user is away. Thus, we note that Plasma display panel (PDP) is an emissive flat panel display where visible light is created by phosphors exited by a plasma discharge between two flat panels of glass. The gas discharge contains no mercury (contrary to the backlights of an active matrix LCD), an insert mixture of noble gases (neon and xenon) is used instead. Dead Pixels, Hot Pixel, Stuck Pixel m A dead pixel is a defective pixel that remains unlit on an LCD screen, monitor, camera, charge- coupled device or CMOS sensor. A permanently lit pixel is a hot pixel, and a pixel that stays on a solid colour is a stuck pixel. Dead pixels can also occur in clusters and these are particularly co annoying and in most cases these can be sent back to the manufacturer. The majority of dead pixels are only noticeable on a solid colour background, for example through the use of the “Dead Pixel Checkers” which consist of four-five solid-colour images. EFT monitors e. All types of monitors are a strain on our eyes. EFT, or Eye Fresh Technology, monitors have a vital coating on the rear that emits anions and far-infrared rays that serve to make the environment m fresh and ease the strain on the eyes and relax the eyes and body Blu Ray Disc ro Blu-ray is currently supported by about 200 of the world’s leading consumer electronics, personal computer, recording media, video game and music companies. Blu-ray, also known as Blu-ray Disc is the name of a next-generation optical disc format that has been jointly developed by the ch Blu-ray Disc Association (BOA). Blu-ray Disc association is a group of world’s leading consumer electronics, personal computer and media companies. The format also has support from all Hollywood studios and countless smaller studios as a successor to today’s Digital Visual Disk format. It was initially launched as “Blu-ray Disc founder group” in 2002 by MIT and nine leading.jk electronic companies: Sony, Panasonic, Pioneer, Philips, Thomson, LG Electronics, Hitachi, Sharp, and Samsung. Why Blue, why not magenta or orange? w We have studied above that Digital Visual Disk uses 650 nm (red) wavelength laser diode light as opposed to 780 nm for Compact Disk (infra red). Blu-ray Disc uses a wavelength of 405 nm, that is w coming in the violet (blue) region of electromagnetic spectrum and that is why this term is used J Blu Ray disc was developed for the following purposes: w 1. Storing larger amounts of data. 2. Enable recording, rewriting and playback of high-definition video (HD) So, the Blu Ray Disk offers more than five times the storage capacity of traditional Digital Visual Disk’s and can hold up to 25GB on a single-layer disc and 50GB on a dual-layer disc. The benefit of using a blue violet laser (405nm) is that it has a shorter wavelength than a red laser (650nm), which makes it possible to focus the laser spot with even greater precision, leading to the packing of data more tightly and stored in less space. The dimension of the Blu Ray disc is same as that of a 22 www.jkchrome.com www.jkchrome.com www.jkchrome.com Compact Disk or Digital Visual Disk. But the HD Digital Visual Disk was also developed as an answer to the Blu ray Discs. This would also succeed the normal Digital Visual Disk. The HD Digital Visual Disk as well as Blu Ray Disc have a single-layer capacity of 15 GB and a dual-layer capacity of 30 GB, while the the HD Digital Visual Disk-Random Access Memory has a single-layer capacity of 20 GB and a dual-layer capacity of 40 GB. The data layer of HD Digital Visual Disk is 0.6 mm below the surface physically protecting the data layer from damage. Digital Versatile Disc (DVD) m Digital Video Disc or Digital Versatile Disc (DVD) is also an optical storage device that looks the same as a compact disc but is able to hold about 15 times as much information and transfer it to the computer about 20 times as fast as a CDROM. The CD and DVD have the same dimensions. co DVDs come in two formats: the DVD-Video and the DVD-ROM (DVD Read Only Memory) format. The DVD-Video format is used for home movie entertainment through a DVD player. Why DVD stores more data than CD? e. Please note that DVD uses 650 nm (red) wavelength laser diode light as opposed to 780 nm for CD (infra red). This permits a smaller pit to be etched on the media surface compared to CDs (0.74 m µm for DVD versus 1.6 µm for CD), allowing in part for DVD’s increased storage capacity. Further, the Blu-ray Disc, the successor to the DVD format, uses a wavelength of 405 nm, and one dual- layer disc has a 50 GB storage capacity. So basically, it is the laser optics that matters in storage ro capacities of various kinds of Discs. Compact Discs (CD) ch Compact Disc (CD) is made of several layers of a type of plastic usually Polycarbonates. The outer layers are protection layers, which simply absorb scratches so that the inner layer holding data remains intact. The inner data layer has small tracks which spiral out from the centre of the disc towards the ends. These tracks ate such tightly wound that the entire length of the track if.jk stretched out in a straight line would stretch over five kilometers. Data is written to the CD-ROM by burning microscopic pits into the reflective surface of the disk with a powerful laser. These spiral tracks have flat reflective areas and non-reflective bumps. A w flat reflective area represents a binary 1, while a non-reflective bump represents a binary 0. The data is stored in a spiral pattern that originates from the centre of the disc and spirals out toward the outer edge. w Data is read from a CD-ROM with a low power laser contained in the drive that reflects infrared light off of the reflective surface of the disk and back to a photo detector. The pits in the reflective w layer of the disk scatter light, while the land portions of the disk reflect the laser light to the photo detector. The photo detector then converts these light and dark spots to electrical impulses corresponding bits. Electronics and software interpret this data and accurately access the information contained on the CD-ROM. A standard 74 min. CD contains 333,000 blocks and each block is 2,352 bytes. Thus, with proper devices and software, one can record and read the data from a CD ROM. It’s worth note that CDROM is manufactured with an organic dye layer that is permanently changes by 23 www.jkchrome.com www.jkchrome.com www.jkchrome.com the laser of the recorder in a pattern that represents the bits and bytes of the data. These are called Write once discs. On the other hand, CD-RW (CD-read/write) are discs, which can be erased and re-recorded with data. Please note that underside of the CD-ROM disk is coated with a very thin layer of aluminum that reflects light Hard Disk of a Computer The hard disk is an internal storage device which holds programs and data used by a computer. It consists of magnetic platters with read/write heads that float above the platters to record and m play back data. In many respects, it is similar to a phonograph turntable. It is susceptible to strong jarring, which could cause the heads to physically damage the disk. The disk is enclosing in an airtight casing to keep it dust-free. HDD is a is a non-volatile, random access digital data storage co device, which was first introduced by IBM in 1956. The Microsoft Operating Systems allow a drive letter assignment such as C Drive, D Drive, E Drive etc.. This is the process of assigning alphabetical identifiers to physical or logical disk drives or partitions (drive volumes) in the root file system namespace. e. Why there is no B drive? m It’s not that computers don’t have B drives. We should be aware that the primitive personal computers didn’t have hard discs. They were equipped with two floppy drives called drives A and B. Later, a hard disk was introduced and was labeled as the C drive. Other drives like the CD drive, ro DVD drive, flash drive and others were labeled D, E, F,G, H etc. The basic question here arrives that how does computer write information to the hard disk. Please note that unlike a cassette, a computer writes information to the hard disk in a sequential ch manner. This means that one file’s a data may be scattered around the disk. When files are deleted, or even edited, blank spaces may appear around the disk. Can a computer have more than one hard disk?.jk Yes. We use usually two kinds of Hard Disks today. IDE (Integrated Drive Electronics) and SCSI (Small Computer System Interface) hard drives. The IDE drives are used in PCs and SCSI in servers. Motherboards usually come with two embedded IDE ports. Each port can have two w devices connected to it on the same data cable for a total of four devices. CD and DVD units are also connected to the IDE ports and counted as one of those four devices. Once we have four devices, then we can add a PCI IDE controller to have more ports to add devices. SCSI hard drives w are connected to a PCI SCSI controller that will be able to accept seven devices for standard SCSI and 15 for the newer, wide SCSI. w Data Storage in a Computer The area within a computer system where data can be left on a longer term basis while it is not needed for processing is called “Data storage”. The mass storage devices include the diskettes, Hard Drives, Optical Disks and Magnetic Tapes. Diskette is a small, removable, flexible plastic disk covered with a thin layer of a magnetisable substance, onto which digital data can be recorded and stored. They are called Floppy Disks and now they are outdated. The Hard Drive is the storage area within the computer itself, where gigabytes of space are available to store bits of information. 24 www.jkchrome.com www.jkchrome.com www.jkchrome.com Then, we have the Optical Disks, which is a storage device that uses reflecting surfaces and laser technology to read and write data on a disk, so also known as Laser Disk. CD-ROM’s are the most popular type of optical storage. CD-ROM stands for Compact Disc Read Only Memory. A computer CD-ROM disk, like its audio counterpart, contains data that has been stamped on the disk surface as a series of pits. To read the data on a CD-ROM an optical read head distinguishes the patterns of pits that represent bytes. CD-ROM disks provide tremendous storage capacity. CD-ROMs usually come with data already written onto them. These days most applications software is provided on CD-ROM. Computer Mouse m A mouse is a handheld device for moving the pointer around the screen. It is a primary component of the windows GUI (Graphical User Interface) environment. The use of the mouse in windows allows the user to point at and clicks on various icons for programs and data files rather than having to type in commands to copy files, open programs, etc. as in the older DOS. co Mouse is invention of Douglas Carl Engelbart. Douglas Carl Engelbart is an American inventor and early computer pioneer and internet pioneer, best known for inventing the Computer Mouse. e. Apart from the mouse, his team also developed the hypertext, networked computers, and precursors to GUIs. m A typical Mouse consists of two buttons, each of which functions differently in windows. A single click of the left button on an icon selects the item, a double click (clicking twice in rapid succession) button will open a pop-up menu offering choices relative to the item clicked. The ro primitive mouse did not contain the roller. Now the intelliMouse includes a roller between the two buttons for easy scrolling up and down, specially while visiting websites. The early mouse contained the touchpad’s, large and small trackballs, and graphics tablets. ch Here we should note that almost all functions that we do with a mouse can be replaced with keyboard commands. The keyboard equivalents are visible in the menus in most programmes. What is Computer Keyboard.jk The standard microcomputer keyboard consists of 104 keys arranged in the standard typewriter or QWERTY layout. A separate numeric keypad is at the right side of the keyboard and can be toggled on or off by pressing the “num lock” key. This numeric keypad may not be found in small w size laptops and keywords. QWERTY comes from the first six letters in the top row. It was invented by C L Sholes in 1872. w Keyboard v/s Game Console w Here we can note that the primary device for the PC is a keyboard and mouse, while all Game console systems come with game pads used to control movement within the game. Technically, a computer game can be thought of as one composed of a computer-controlled virtual universe. A video game is a computer game where a video display is the primary feedback, which is displayed on a television screen. It is the console system that takes advantage of the plug-and-play feature — there is no need to install the software or get different graphic cards, faster processors or CPU chips. 25 www.jkchrome.com www.jkchrome.com www.jkchrome.com Flash Memory Flash memory is a form of non-volatile computer memory that can be electrically erased and reprogrammed. Flash memory applications include digital audio players, digital cameras and mobile phones. Flash memory is also used is USB flash drives (Thumb drives, handy drive), which are used for general storage and transfer of data between computers. It has also gained some popularity in the gaming market, where it is often of EEPROM or battery-powered SRAM for game save data. SDRAM & DDR SDRAM m Synchronous dynamic random access memory (SDRAM) is DRAM that is synchronized with the system bus. DRAM has an asynchronous interface, which means that it responds as quickly as possible to changes in control inputs. SDRAM has a synchronous interface, meaning that it waits co for a clock signal before responding to control inputs and is therefore synchronized with the computer’s system bus. The clock is used to drive an internal finite state machine that pipelines incoming instructions. This allows the chip to have a more complex pattern of operation than an asynchronous DRAM, enabling higher speeds. e. Double data rate (DDR) SDRAM was a later development of SDRAM, used in PC memory beginning in 2000. DDR2 SDRAM was originally seen as a minor enhancement (Based upon the industry standard single-core CPU) on DDR SDRAM that mainly afforded higher clock speeds and m somewhat deeper pipelining. However, with the introduction and rapid acceptance of the multi- core CPU in 2006, it is generally expected in the industry that DDR2 will revolutionize the existing physical DDR-SDRAM standard. Further, with the development and anticipated introduction of DDR3 in 2007, it is anticipated DDR3 will rapidly replace the more limited DDR and Newer DDR2. ro SRAM v/s DRAM v/s VRAM ch Dynamic Random Access Memory (DRAM) is a type of random access memory that stores each bit of data in a separate capacitor within an integrated circuit. Since real capacitors leak charge, the information eventually fades unless the capacitor charge is refreshed periodically. Because of this refresh requirement, it is a dynamic memory as opposed to SRAM and other static memory. Its.jk advantage over SRAM is its structural simplicity; only one transistor and a capacitor are required per bit, compared to six transistors in SRAM. This allows DRAM to reach very high density. Since DRAM loses its data when the power supply is w removed, it is in the class of volatile memory devices. VRAM is a dual-ported version of DRAM formerly used in graphics adaptors. It is now almost obsolete, having been superseded by SDRAM and SGRAM. VRAM has two paths (or ports) to its memory array that can be used simultaneously. w RAM v/s ROM and Primary Storage w RAM is also volatile, losing the stored information in an event of power loss, and quite expensive. ROM is not volatile, but is not suited to storage of large quantities of data because it is expensive to produce. Primary Storage is also known as internal memory. It is the computer memory that is accessible to the CPU of a computer without the use of computer’s input/output channels. Primary storage is used to store that is likely to be in active use. Primary storage is typically very fast, as in the case of RAM. But, ROM must also be completely erased before it not impossible. Therefore, separate secondary storage, or external memory, is usually required for long-term persistent storage. Primary storage may include several types of storage, such as main storage, cache memory, and special registers, all of which can be directly accessed randomly, that is, accessing 26 www.jkchrome.com www.jkchrome.com www.jkchrome.com any location in storage at any moment takes the same amount of time. ROM v/s RAM Read-only memory (ROM) is a class of storage media used in computers and other electronic devices. It’s easily cannot be written to, its main use lie in the distribution of software. Some ROMs can be erased and re-programmed multiple times, although they are still referred to as ” read only” because the reprogramming process involves relatively infrequent, complete erasure and reprogramming, not the frequent, bit-or word at a time updating that is possible with RAM. Random access memory (RAM) is a type of data store used in computers that allows the stored m data to be accessed in any order-that is, at random, not just in sequence. Generally RAM in a computer is considered main memory or primary storage; the working area and data. This type of RAM is usually in the form of integrated circuits (ICs). These are commonly called memory sticks co or RAM sticks because they are manufactured as small circuit boards with plastic packaging personal computers have slots for adding and replacing memory sticks. Most RAM can be both written to and read from, so “RAM” can both written to and read from, so “RAM” is often used interchangeably with “read-write memory”. In this sense , RAM is he “opposite” of ROM, but in a more true sense, of sequential access. e. PROM, FPROM and ROM  m A programmable read-only memory (PROM) or field programmable read-only memory (FPROM) is a form of digital memory where the setting of each bit is locked by a fuse or antifuse. Such PROMs are used to store programs permanently. They are most commonly ro seen in computer games or such products as electronic dictionaries, where PROMs for different languages can be substituted. Common PROM comes with all bites reading as 1. Burning a fuse during programming causes its bit to read as 0. The memory can be programmed just once after manufacturing by “blowing” the fuses (using a PROM blower), ch which is an irreversible process. Blowing a fuse opens a connection while blowing an antifuse closes a connection. Programming is done by applying high-voltage pulses which are not encountered during normal operation (typically 12 to 21 volts).  Read-only means that, unlike the case with conventional memory, the programming.jk cannot be changed (at least not by the end user). Random Access Memory (RAM) w RAM is an acronym for random access memory, a type of computer memory that can be accessed randomly. that is, any byte of memory can be accessed without touching the preceding bytes.A Computer Memory refers to the temporary internal storage areas within a computer. The w term memory is usually used as shorthand for ‘physical memory’, which refers to the actual chips capable of holding data. Some computers also use ‘virtual memory’, which expands physical memory onto a hard drive. w The main type of memory and the most familiar to users is random access memory (RAM). Random Access Memory is the same as main memory. A computer can both write data into Random Access Memory and read data from Random Access Memory. Any time we turn on a computer, a set of operating instructions is copied from the hard disk into Random Access Memory. These instructions, which help control basic computer functions, remain in RAM until the computer is turned off. Most Random Access Memory is volatile, which means that it requires a steady flow of electricity to maintain its contents. As soon as the power is turned 27 www.jkchrome.com www.jkchrome.com www.jkchrome.com off, whatever data was in RAM disappears. The contents of RAM are necessary for the computer to process data. The results of the processing are kept temporarily in RAM until they are needed again or until they are saved onto the hard disk or other storage device. Storage capacity of Random Access Memory is measured in megabytes (MB) and Giga Bytes (GBs). A 64 MB Random Access Memory means that it can hold 64 million bytes of data (a standard A4 page of text typically holds about 2,048 bytes or characters of text). Other types of memory include. Bytes v/s Octets v/s Nibble m The term byte initially meant the smallest addressable unit of memory. In the past, 5-,6-,7-,8-, and 9-bit bytes have all been individual bits (bit-addressed machine) or that could only address 16-or 32-bit quantities (bit-addressed machine).The term byte was usually not used at all in connection co with bit- and word-addressed machines. However, term octet always refers to an 8-bit quantity. Today, it mostly used in the field of computer networking, where computers with different bytes widths might have to communicate. A nibble is a four-bit aggregation, or half an octet. As a nibble contains 4 bits, there are sixteen e. (24) possible values, so a nibble corresponds to a single hexadecimal digit (thus, it is often referred to as a “hex digit” or “hexit” Understanding Bits and Bytes m A bit refers to binary digit. It refers to a digit in the binary numeral system, which consists of base ro 2 digits (i.e. there are only 2 possible values; 0 or 1). This means that the number 10010111 is 8 bits long. Thus Bit is used as a variable or computed quantity that can have only two possible values. These two values are often interpreted as binary ch digits and are usually denoted by the Arabic numerical digits 0 and 1. Binary digits are almost always used as the basic unit of information storage and communication in digital computing and digital information theory. The bit is also a unit of measurement, the information capacity of one binary digit..jk There are several units of information which are defined as multiples of bits, such as byte (8 bits), kilobit (either 1000 or 210 = 1024 bits). w A kilobyte is a unit of information or computer storage equal to either 1024 or 100 bytes. It commonly abbreviate as Kb, KB or Kbyte. The term “kilobyte” was first used to refer to a value of 1024 bytes (210), because the binary nature of digital computers lends itself to quantities that are w powers of two, and 210 is roughly one thousand. This misuse of the SI prefixes spread from the slang of computer professionals into the mainstream lexicon, creating much confusion, between the Kilo and Kilobyte. w A megabyte is a unit of information or computer storage equal to approximately one million bytes. It is commonly abbreviated MB. Mb is used for megabits. A gigabyte (derived from the SI prefix giga)is a unit of information or computer storage equal to one billion (that is, a thousand million)bytes. 1,073,741,824 bytes, equal to 10243, or 230 bytes. This is the definition used for computer memory sizes, and most often used in computer engineering, computer science, and most aspects 28 www.jkchrome.com www.jkchrome.com www.jkchrome.com of computer operating systems. The IEC recommends that this unit should instead be called a gibibyte (abbreviated GiB), as it conflicts with SI units for bus speeds and the lik Complementary Metal Oxide Semiconductor (CMOS)  CMOS is an abbreviation for Complementary Metal Oxide Semiconductor. CMOS technology is used in microprocessors, microcontrollers, static RAM, and other digital logic circuits. CMOS technology is also used for several analog circuits such as image sensors (CMOS sensor), data converters, and highly integrated transceivers for many types of communication.  CMOS uses a complimentary arrangement of NMOS and PMOS, Negative And Positive m Metal Oxide Transmitter Circuits. CMOS memory draws very little current (Nano-amps). Values stored in it can be maintained for very a long period of time while the computer is off with a rechargeable lithium battery. The CMOS memory is used to store system configuration information, such as disk drive parameters, memory configuration and co setup program.  CMOS memory is used by the basic input output system (BIOS), a program permanently stored in the flash memory as disk drive parameters, memory configuration, and the date- time, some of which we enter in the CMOs setup program. CMOS setup is part of the BIOS e. program.  The CMOS memory is usually located with the real-time clock in the motherhood chipset or in a separate real-time clock chip. It is located in the chipset on most recent motherboards. m What is difference between Cold Boot and Warm Boot? ro We actually perform a Cold Boot every time we turn on the power switch of our computer. To “boot” the computer means to start it up and reset the memory and BIOS. Sometimes, the programme running hangs and we press the ctrl-alt-delete keys simultaneously. This is called ch Warm Boot. So, when a computer stops responding because of memory problems or the “blue screen of death” appears, we need to do a warm boot. The latest operating system Windows 7 responds with task manager when we press the ctrl-alt-delete keys simultaneously. We can choose the not responding programmes to close and continue. However, if the warm boot fails to restart the computer, we need to resort to a cold boot by shutting off the power switch, waiting.jk few seconds and then turning it back on. Basic Input/Output System (BIOS) w  BIOS refers to basic input/output system (BIOS). BIOS software is built into the PC, and is the first code run by a PC when powered on, and that is why it is called boot firmware. w  In computing, firmware is software that is embedded in a hardware device. It is often provided on flash ROM or as a binary image file that can be uploaded onto existing hardware by a user. When we turn on the power switch, computer will make some beeps w while it goes through a self-check of the system components. If we want to change any of the setup options, such as setting a password for the system, changing the sequence for booting up the computer., or reconfiguring any other hardware, we need to press the F2 or any other key recommended by the hardware provider to access the keyBIOS settings. The BIOS includes very basic information about the hardware to get the computer started before the operating system software takes over. Once the operating system takes over, more detailed information about the hardware is loaded into the computer’s RAM and windows starts up. 29 www.jkchrome.com www.jkchrome.com www.jkchrome.com  Thus, primary function of the BIOS is to set up the hardware and load and start an operating system. When the PC starts up, the first job for the BIOS is to initialize and identify system devices such as the video display card, keyboard and mouse, hard disk drive, optical disc drive and other hardware. The BIOS then locates software held on a peripheral device (‘boot device’), such as a hard disk or a CD/DVD, and loads and executes that software, giving it control of the PC. This process is known as booting. Booting is synonymous with a booting up, which is short for bootstrapping. Computer Port A hardware computer port is a physical interface between a computer and other computers or m devices. A software computer port is a virtual data connection between computer programs possibly through a computer network. co The Hardware ports com