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Commonly used operating system UNIX: Pronounced yoo-niks, a popular multi-user, multitasking operating system developed at Bell Labs in the early 1970s. UNIX was one of the first operating systems to be written in a high-level programming language, namely C. This meant that it could be installed on virtually any computer for which a C compiler existed. LINUX: Pronounced lee-nucks or lih- nucks. A freely-distributable open source operating system that runs on a number of hardware platforms. The Linux kernel was developed mainly by Linus Torvalds and it is based on Unix. Because it’s free, and because it runs on many platforms, including PCs and Macintoshes, Linux has become an extremely popular alternative to proprietary operating systems. Windows: Microsoft Windows is a series of graphical interface operating systems developed, marketed, and sold by Microsoft. Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces (GUIs). Microsoft Windows came to dominate the world’s personal computer market with over 90% market share, overtaking Mac OS, which had been introduced in 1984.The most recent client version of Windows is Windows 7; the most recent server version is Windows Server 2008 R2; the most recent mobile version is Windows Phone 7.5. * Android: Android is a Linux-based mobile phone operating system developed by Google. Android is unique because Google is actively developing the platform but giving it away for free to hardware manufacturers and phone carriers who want to use Android on their devices. * Symbian: Symbian is a mobile operating system (OS) targeted at mobile phones that offers a high-level of integration with communication and personal information management (PIM) functionality. Symbian OS combines middleware with wireless communications through an integrated mailbox and the integration of Java and PIM functionality (agenda and contacts). The Symbian OS is open for third-party development by independent software vendors, enterprise IT departments, network operators and Symbian OS licensees. LANGUAGE PROCESSORS: Since a computer hardware is capable of understanding only machine level instructions, So it is necessary to convert the HLL into Machine Level Language. There are three Language processors: A. Compiler: It is translator which coverts the HLL language into machine language in one go. A Source program in High Level Language get converted into Object Program in Machine Level Language. B. Interpreter: It is a translator which converts the HLL language into machine language line by line. It takes one statement of HLL and converts it into machine code which is immediately executed. It eliminate the need of separate compilation/run. However, It is slow in processing as compare to compiler. C. Assembler: It translate the assembly language into machine code. Microprocessor: A microprocessor is a semiconductor chip, which is manufactured using the Large Scale integration (LSI) or Very Large Scale Integration (VLSI), which comprises Arithmetic Logic Unit, Control unit and Central Processing Unit (CPU) fabricated ona single chip. The size of a bus, known as its width, is important because it determines how much data can be transmitted at one time. For example, a 16-bit bus can transmit 16 bits of data, whereas a 32-bit bus can transmit 32 bits an ‘Control Bus > > > ‘Address Bus Clock speed: Also called clock rate, the speed at which a microprocessor executes instructions. Every computer contains an internal clock that regulates the rate at which instructions are executed and synchronizes all the various computer components. The CPU requires a fixed number of clock ticks (or clock cycles) to execute each instruction. The faster the clock, the more instructions the CPU can execute per second. Clock speeds are expressed in megahertz (MHz) or gigahertz ((GHz). 16 bit Microprocessor: It indicates the width of the registers. A 16-bit microprocessor can process data and memory addresses that are represented by 16 bits. Eg. 8086 processor 32 bit Microprocessor: It indicates the width of the registers. A 32-bit microprocessor can process data and memory addresses that are represented by 32 bits. Eg. Intel 80386 processor, Intel 80486 64 bit Microprocessor: It indicates the width of the registers; a special high- speed storage area within the CPU. A 32- bit microprocessor can process data and memory addresses that are represented by 32 bits. Eg. Pentium dual core, core 2 duo. 128 bit Microprocessor: It indicates the width of the registers. A 128-bit microprocessor can process data and memory addresses that are represented by 128 bits. Eg. Intel core i7 Difference between RISC & CISC architecture RISC (Reduced Instruction Set Computing): 1. RISC system has reduced number of instructions. 2. Performs only basic functions. 3. All HLL support is done in software. 4. All operations are register to register. CISC (Complex Instruction Set Computing): 1. A large and varied instruction set. 2. Performs basic as well as complex functions. 3. All HLL support is done in Hardware. 4. Memory to memory addressing mode USB (Universal Serial Bus): It is a newer type of serial connection that is much faster than the old serial ports. USB is also much smarter and more versatile since it allows the “daisy chaining” of up to 127 USB peripherals connected to one port. It provides plug & play communication. PS/2 Port: PS/2 ports are special ports for connecting the keyboard and mouse to some PC systems. This type of port was invented by IBM FireWire Port: The IEEE 1394 interface, developed in late 1980s and early 1990s by Apple as FireWire, is a serial bus interface standard for high-speed communications and isochronous real- time data transfer. The 1394 interface is comparable with USB and often those two technologies are considered together, though USB has more market share. Infrared Port: An IR port is a port which sends and receives infrared signals from other devices. It is a wireless type port with a limited range of 5-10ft. Bluetooth: Bluetooth uses short-range radio frequencies to transmit information from fixed and mobile devices. These devices must be within the range of 32 feet, or 10 meters for Bluetooth to effectively work. A Bluetooth port enables connections for Bluetooth-enabled devices for synchronizing. Typically there are two types of ports: incoming and outgoing. The incoming port enables the device to receive connections from Bluetooth devices while the outgoing port makes connections to Bluetooth devices. Internal Storage encoding of Characters: ASCII (American standard code for information interchange): ASCII code is most widely used alphanumeric code used in computers. It is a 7- bit code, and so it has 2” =128 possible code groups. It represents all of the standard keyboard characters as well as control functions such as Return & Linefeed functions. ISCII (American standard code for information interchange): To use the Indian language on computers, ISCII codes are used. It is an 8-bit code capable of coding 256 characters. ISCII code retains all ASCII characters and offers coding for Indian scripts also. B. Binary Number System: In Binary Number system there are only two digits i.e. 0 or 1. It is base-2 system. It can be used to represent any quantity that can be represented in decimal or other number system. It is a positional value system, where each binary digit has its own value or weight expressed as power of 2. The following are some examples of binary numbers: 1011015 115 1011% Conversion from Decimal to Binary or Binary to Decimal Convert from decimal to binary “a r X ao) - Kon ews se! Integer Xa) > Xp Binary Div | Quotient | Remainder | Number (X) 45 22 7 1 /2 22 11 0 01 /2 11 5 7 101 /2 5/ 22 | 1101 2 2/ 1 0 01101 2 1/ 0 1 101101 2 Fractional Part 0.180... >X, Index the digits of the number 190413120119.010%1°30419161°7 Multiply each digit 1*25 +0*24 +1*23 +1*22 +0*2! +1*29 +0#2° 1 40*22 +1*2°3 +0424 +1429 +1426 +1427 32+04+8+44+04+14+0+04+0125+0+ 0.03125 + 0.015625 + 0.007813 = 45.179688(10) C. Octal Number System: It has eight unique symbols i.e. 0 to 7. It has base of 8. Each octal digit has its own value or weight expressed as a power of 8. D. Hexadecimal Number System: The hexadecimal system uses base 16. It has 16 possible digit symbols. It uses the digits 0 through 9 plus the letters A, B, C, D, E, F as 16 digit symbols. Each hexadecimal digit has its own value or weight expressed as a power of 16. 
