The CPU:As previously in the text about microprocessor,the CPU or central processing unit is the brain of the computer. In terms of computing power,the CPU is the most important element of a computer system as it is where most calculations take place.On large machines,CPUs require one or more printed circuit boards while on personal computers and small workstations,the CPU is housed in a single chip called a microprocessor.The CPU performs the actual processing of data which are obtained via the system bus which is a set of conductors that enable information to be transmitted between computer components,such as printers,modems,and monitors.In addition to computation,the CPU controls and co-ordinates the operations of the other major components. The CPU has two main components,namely:
-the ALU(arithmetic logic unit),which performs arithmetic and logical operations,comparisons and logical decisons following the instructions given by the CU and the rules of boolen algebra. -the CU(control unit) which extracts instructions from memory,decodes and executes them,producing signals which control the other parts of the computr.this may cause it to transfer data between memory and ALU or to activate peripherals to perform input and output operations. A CPU includes also a collection of registers,small high-speed memory circuits used to hold data temporary and keep track of the adress of the instructions being executed;a series of buses that join the various components together;a clock which regulates and synchronises all the operations and buffers that are interfaces between the processor and the outside world.
HOW DOES THE CPU WORK?:- PAR.1:The main function of the CPU is to perform arithmetic and logical oprerations on data taken from memory or on information entered trhough some device,such as a keyboard,scanner,or joystick. - PAR.2:The CPU is controlled by a list of software instructions,called a computer program.These instructions pass into the computer's main random access memory (RAM),where each instruction is given a unique address,or memory location. - PAR.3:Data flow through an interface unit of wires called the bus which connects the CPU to RAM. - PAR.4:The data are then decoded by a processing unit called the instruction decoder that interprets and implements software instructions. - PAR.5:The main instruction decoder the data pass to the arithmetic/logic unit (ALU),which performs calculations and comparisons.Data may be stored by the ALU in temporary memory locations called registers where it may be retrieved quickly. -PAR.6:During this process,a unit called the program counter keeps track of each succesive instruction to make sure that the program instructions are followed by the CPU in the correct order. - PAR.7:The CPU is driven by one or more repetitive clock circuits that send a costant stream of pulses throughout the CPU's circuitry.The CPU uses these clock pulses to synchronise its operations.Clock pulses are a measure of the speed of a processor
RAM:This is the main memory where data can be stored temporarily until the current flows through the circuit. The RAM is volatile,which means it requires a constant flow of electricity to keep its contents and is erasable, that new data can be written in place of old. There are different types of random access memory: Static RAM (SRAM) contains information until you turn on and is usuallyused as cache memory because it works very quickly. Othertypes of memory, dynamic RAM (DRAM), is slower than SRAM and must be periodically updated with electricity or information in its possession will be lost. The DRAM is cheaper than SRAM and acts as the main memory in most computers
ROM:(Read Only Memory) contains the essential information andsoftware that must be kept available for the operation of your computer, such as the operating system that directs the actions of the computer from the startup to shutdown, the ROM is callednonvolatile memory in as the memory chip does not loseinformation when the computer is off. C 'is also a PROM(programmable read only memory) which is a memory chip on which you can store a program, such as ROM, and is not volatile, and an EPROM (programmable read only memory and erasable)which is a special type of PROM that can be erased by exposing it to ultraviolet light.
BIOS:Basic input / output system, the part of the computer operating system that manages communications between a program andexternal devices.
CACHE:a small buffer storage quickly integrated into the central processing unit that contains the most frequently used commandsand and helps to streamline operations and file access.
Optical storage: This category includes the familiar CD (compact disc) or CD-ROM that can store huge amounts of digital information (783 MB), ilCDR (recordable CD), the CDRW(riscrivibileCD) and the DVD. Compact discs (CDs) store the information on the box bruciatosulla surface of a disc of reflective material. CD-ROM can memorizzarequante more information onhard disks, but have a slower rate of information retrieval. Adigital versatile disc (DVD) looks and works like a CD-ROM, butpuòmemorizzare more than 15 times as much information.
solid-state storage: essentially means that there are no moving parts and is a popular storage fittamolto rimovibiliper small devices such as digital cameras, handheld devices, laptops, mobile music voters. It includes flash memory devices, storageFlash or Smart Media cards qualiCompact can reach a capacity of 4 GB and higher. They offer re-adjustability, power and smallsize senzastoccaggio. Some devices need more than one purpose. For example, the discs can be utilizzaticome ifcontengonoinformazioni input devices to be used and processed by the computer user. In addition, they can be used as output devices, if the user wants to store risultatidei calculations on them.
USB PEN DRIVE:It is a completely external potable drive which has become popular largely because of the USB technology.Pen drives are also know as flash drives,keydrivers,USB sticks or thumb drives and are typically small,lightweight devices,around 50 mm long and weighing only around 50 g.They have a drive,a flash memory and media all in one sealed case and connect to the PC via the USB cable.Their capacity ranges from 16 MB of the cheapest ones to a few GBs.A pen drive consist of a small printed circuit board with a plastic casing,making it study enough to be carried around in a pocket or in your key ring.Pen drives do not even require an external power source or battery when not in use.They are more durable and resistant than floppy disks or CDs and this makes them ideal for transporting personal data or work files from one location or another.
file di word:
http://www.megaupload.com/?d=QMBP0CLL
file di word:
http://www.megaupload.com/?d=QMBP0CLL
