computer architecture :: essays papers

computer architectureComputer architecture covers the design of system software,such as the operating system (the program that surmounts the computer), aswell as referring to the combination of hardware and basic software thatlinks the machines on a computer ne 2rk. Computer architecture refers toan entire structure and to the expatiate needed to make it functional. Thus,computer architecture covers computer systems, microprocessors, circuits,and system programs. Typically the term does not refer to applicationprograms, such as spreadsheets or enunciate touch on, which are required toperform a task but not to make the system run.In designing a computer system, architects consider quintet majorelements that make up the systems hardware the arithmetic/logic unit,control unit, memory, input, and output. The arithmetic/logic unit performsarithmetic and compares numerical values. The control unit directs the summons of the computer by taking the user instructions and transformingthem into electrical signals that the computers circuitry can understand.The combination of the arithmetic/logic unit and the control unit is calledthe central processing unit (CPU). The memory stores instructions anddata. The input and output sections allow the computer to receive andsend data, respectively.Different hardware architectures are required because of thespecialized inescapably of systems and users. One user may need a system todisplay graphics extremely fast, while another system may have to beoptimized for searching a database or conserving battery power in a laptopcomputer.In addition to the hardware design, the architects must considerwhat software programs go forth operate the system. Software, such asprogramming languages and operating systems, makes the details of thehardware architecture invisible to the user. For example, computers that usethe C programming language or a UNIX operating system may appear thesame from the users viewpoint, although they use differen t hardwarearchitectures.When a computer carries out an instruction, it proceedsthrough five steps. First, the control unit retrieves the instruction frommemoryfor example, an instruction to add two numbers. Second, thecontrol unit decodes the instructions into electronic signals that control thecomputer. Third, the control unit fetches the data (the two numbers).Fourth, the arithmetic/logic unit performs the specific operation (theaddition of the two numbers). Fifth, the control unit saves the result (thesum of the two numbers).Early computers used merely simple instructions because thecost of electronics capable of carrying out complex instructions was high.As this cost decreased in the 1960s, more complicated instructionsbecame possible. mixed instructions can save time because they makeit unnecessary for the computer to retrieve additional instructions. Forexample, if seven operations are combined in unitary instruction, then six of