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Types Of ComputersComputers are distinguished on the basis of their processing capabilities.- Supercomputers are the computers with the most processing power. The primary application of supercomputers has been in scientific and military work, but their use is growing rapidly in business. - Mainframes are not as powerful and generally not as expensive as supercomputers. Large corporations, where data processing is centralizedand large databases are maintained, most often use mainframe computers. - Minicomputers are smaller and less expensive than mainframe computers. They are usually designed to accomplish specific tasks such as process control and engineering applications. Larger companies gain flexibility by distributing minicomputers in organizational units instead of centralizing at one location.- Servers typically support computer networks, enabling users to share files, software, peripheral devices and other network resources. Server farms are large groups of servers.- Workstations provide high levels of performance to technical users such as designers and are typically based on RISC (reduced instruction set computing) architecture.- Microcomputers or personal computers (PCs), are the smallest and least expensive category of general-purpose computers. They may be subdivided into five classifications:o Desktops o Thin clientso Laptopso Notebooks,o Mobile device- Desktop personal computer is the typical, familiar microcomputer system.Thin-client systems are desktop computer systems that do not offer the full functionality of a PC.- Notebooks are smaller laptops.- Mobile devices as handheld computers, often called personal digital assistants (PDAs) or handheld personal computersThe MicroprocessorThe central processing unit (CPU) is the center of all computerprocessing activities, where all processing is controlled, data are manipulated, arithmetic computations are performed, and logical comparisons are made.The CPU consists of the- Control unit - Arithmetic-logic unit (ALU)- Primary storage (or main memory)The Machine Instruction CycleThe cycle of processing is called the machine instruction cycle and it speed depends on the following four factors of chip design:- The preset speed of the clock that times all chip activities, measured in megahertz (MHz), millions of cycles per second, and gigahertz (GHz), billions of cycles per second. The faster the clock speed, the faster the chip.- The word length, which is the number of bits (0s and 1s) that can be processed by the CPU at any one time. The majority of current chips handle 32-bit word lengths, and the Pentium 4 is designed to handle 64-bit word lengths. The larger the word length, the faster the chip.- The bus width. The wider the bus (the physical paths down which the data and instructions travel as electrical impulses), the more data can be moved and the faster the processing. A bus transfers data is measured in megahertz.- The physical design of the chip - the distance between transistors is known as line width. The smaller the line width, the more transistors can be packed onto a chip, and the faster the chip.The Evolution of The MicroprocessorMoore’s Law - Gordon Moore’s 1965 prediction that microprocessor complexity would double approximately every two years is based on the following changes: Increasing miniaturization of transistors, Compacting the physical layout of the chip’s components (decreasing line width) and using better conducting materials.The arrangement of the components and their interactions is called computer architecture. Computer architecture includes the instruction set and the number of the processors, the structure of the internal buses, the use of caches, and the types of input/output (I/O) device interfaces.- An instruction set is the set of machine instructions that a processor recognizes and can execute. Complex instruction set computers (CISC) and reduced instruction set computers (RISC), dominate the processor instruction sets of computer architectures. o A CISC processor contai ns more than 200 unique coded commands, one for virtually every type of operation.o The other, a more recent approach is RISC processors, which eliminate many of the little-used codes found in the complex instruction set.Primary StoragePrimary storage, or main memory, stores data and program statements for the CPU. It has four basic purposes:1. To store data that have been input until they are transferred to the ALU for processing. 2. To store data and results during intermediate stages of processing. 3. To hold data after processing until they are transferred to an output device. 4. To hold program statements or instructions received from input devices and from secondary storage.Categories of MemoryThere are two categories of memory: the register, which is part of the CPU and very fast and the internal memory chips, which reside outside the CPU and are slower. The control unit, the CPU, and the primary storage all have registers. Small amounts of data reside in the register for very short periods, prior to their use. Internal memory is used to store data just before they are processed by the CPU. Immediately after the processing it comprises two types of storage space: RAM and ROM.- Random-access memory (RAM) is the place in which the CPU stores the instructions and data it is processing.o Dynamic random access memories (DRAMs)o Synchronous DRAM (SDRAM)- Read-only memory (ROM) is that portion of primary storage that cannot be changed or erased. ROM is nonvolatileo Programmable read-only memory (PROM) o Erasable programmable read-only memory

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IET Lucknow CPF 12 - Types of Computer Notes

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