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Cache Memory: Cache memory is random access memory (RAM) that a computer microprocessor can access more quickly than it can access regular RAM. As the microprocessor processes data, it looks first in the cache memory and if it finds the data there (from a previous reading of data), it does not have to do the more time-consuming reading of data from larger memory. It is of two types- L1 cache is on the same chip as the microprocessor. L2 is usually a separate static RAM (SRAM) chip. Secondary Memory: A. Hard Disk (Local Disk) B. Optical Disks: CD-R, CD-RW, DVD-R, DVD-RW C. Pen Drive D. Floppy Disks F. Memory Cards G. External Hard Disk H. Blu Ray Disk Units of Memory: The smallest unit is bit, which mean either Oor1. 1 bit=Oor1 1 Byte = 8 bit 1 Nibble = 4 bit 1 Kilo Byte = 1024 Byte= 2!° Byte 1 Mega Byte = 1024 KB= 2!° KB 1 Gega Byte = 1024 MB= 2'° MB 1 Tera Byte = 1024 GB= 2!° GB 1 Peta Byte =1024 TB= 2'° TB 1 Exa Byte =1024 PB= 2'° PB 1 Zetta Byte = 1024 EB= 2'° EB 1 Yotta Byte = 1024 ZB= 2'° ZB Booting The process of loading the system files of the operating system from the disk into the computer memory to complete the circuitry requirement of the computer system is called booting. Types of Computer On the basis of working principle a) Analog Computer An analog computer is a form of computer that uses continuous physical phenomena such as electrical, mechanical, or hydraulic quantities to model the problem being solved. Eg: Thermometer, Speedometer, Petrol pump indicator, Multimeter c) Hybrid Computer (Analog + Digital) A combination of computers those are capable of inputting and outputting in both digital and analog signals. A hybrid computer system setup offers a cost effective method of performing complex simulations. The instruments used in medical lies in this category. On the basis of Size a) Super Computer The fastest type of computer. Supercomputers are very expensive and are employed for specialized applications that require immense amounts of mathematical calculations. For example, weather forecasting requires a supercomputer. Other uses of supercomputers include animated graphics, fluid dynamic calculations, nuclear energy research, and petroleum exploration. PARAM, Pace & Flosolver are the supercomputer made in India. b) Mainframe Computer A very large and expensive computer capable of supporting hundreds, or even thousands, of users simultaneously. In the hierarchy that starts with a simple microprocessor (in watches, for example) at the bottom and moves to supercomputers at the top, mainframes are just below supercomputers. In some ways, mainframes are more powerful than supercomputers because they support more simultaneous programs. But supercomputers can execute a single program faster than a mainframe. iii. Palmtop Computer/Digital Diary /Notebook /PDAs: a hand-sized computer. Palmtops have no keyboard but the screen serves both as an input and output device. e) Workstations A terminal or desktop computer in a network. In this context, workstation is just a generic term for a user's machine (client machine) in contrast to a “server’ or “mainframe.” Software Software, simply are the computer programs. The instructions given to the computer in the form of a program is called Software. Software is the set of programs, which are used for different purposes. All the programs used in computer to perform specific task is called Software. Types of software 1. System software: a) Operating System Software DOS, Windows XP, Windows Vista, Unix/Linux, MAC/OS X etc. b) Utility Software Windows Explorer (File/Folder Management), Compression Tool, Anti- Virus Utilities, Disk Defragmentation, Disk Clean, BackUp, WinZip, WinRAR etc... c) Language Processors Compiler, Interpreter and Assembler 2. Application software: a) Package Software/General Purpose software Ms. Office 2003, Ms. Office 2007, Macromedia (Dreamweaver, Flash, Freehand), Adobe (PageMaker, PhotoShop) b) Tailored or Customized Software School Management system, Inventory Management System, Payroll system, financial system etc. * Multi User Systems: Provides regulated access for a number of users by maintaining a database of known users. Refers to computer systems that support two or more simultaneous users. Another term for multi-user is time sharing. Ex: All mainframes are multi-user systems. Example: Unix ¢ Multi-tasking and Single-tasking Operating Systems: When a single program is allowed to run at a time, the system is grouped under the single- tasking system category, while in case the operating system allows for execution of multiple tasks at a time, it is classified as a multitasking operating system. * Distributed Operating System: An operating system that manages a group of independent computers and makes them appear to be a single computer is known as a distributed operating system. Distributed computations are carried out on more than one machine. When computers in a group work in cooperation, they make a distributed system. 
