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System unit
The system unit is the core of a computer system; it thinks and tells the computer what to do. The most important of this components is the motherboard that contents Central Processing Unit ( CPU) or microprocessor , which acts as the "brain" of your computer. Another computer is Random Access Memory ( RAM), which temporarily stores information that CPU uses while the computer is on. Information stored in RAM is erased when the computer is turned off.
Two parts of the system Unit
a- External Parts : these are the parts that are found outside the system unit. Power Switch – used to turn the computer on and off. Disk Drive – where diskettes are inserted. Casing – a metal cover that protects all the parts inside the unit. Reset Switch- used to restart the computer. LED- the lights found in front of the system unit. UBS b- Internal Parts : these are the parts that are found inside the system unit. Motherboard – a large printed circuit board where the processors, cards, and memory chips are placed.
Micro processing- known as the CPU. It is the brain of the computer. Many computers making cup, such that Intel, AMD and IBM.
ROM and RAM.
Power Supply- it gives the system unit power to process commands.
Fan – it cools the microprocessor inside the system unit to avoid overheating. Hard Disk- disk that can store a lot of information. Video Card- it generates the visual output from your system to the monitor.
Slots- for card are inserted. System Clock- controls the timing within a computer, and help determine the speed of the implementation of computer operations are measured in HZ, which represents one pulse per second, so measured in Megahertz measured by the fact that the computer result in millions of pulses per second. System clock battery- it keeps the computer clock accurate even if it is turned off.
Central Processing Unit ( CPU)
This unit consists of the following parts
1- Control Unit- controls all the operation that are performed by the CPU.. 2- Arithmetic Logic Unit (ALU) – is mainly used to perform arithmetic and logical operations. 3- Main Memory Unit (MMU) - is used to store data and information. RAM (Random Access Memory). ROM ( Read only Memory ) Secondary Memory.
This supports the main memory. It also stores data and information for future use.
Type of Secondary Memory
Hard disk drive:- It acts as a giant disk inside the system unit. It has a bigger storage capacity compared to a floppy disk. It can provide long-term data storage inside the computer. Disks:- these are round and flat disks used for saving and entering data during processing. Compact disk: -It can be carried anywhere. It is less expensive than the hard disk. It can store more information than the floppy disk. DVD: - (digital versatile disk or digital video disk). CD- ROM :- (Compact Disc- Read- Memory) Types of compact Disk CD-ROM:- (Compact Disk Read Only Memory): Read CD_ROM and CD_R. CD_ROM multi- read: Read CD-ROM, CD-R. CD_R (Compact Disk Recordable): read CD-ROM and CD-R Write once on special disks named CD-R. CD-RW (Compact Disk Rewritable):- Read CD-ROMs and CD-R write and re-write on special disks (CD-RW). DVD-RAM (Digital Versatile Disk Random Access Memory):- Reads all CD formats. Reads DVD ROM. Read and writes DVD disks, ex. DVD-R, DVD-RW. Floppy disk (A):- (or diskette) it is a small ( 1.43MB. 3. inch), removable storage device. It is less expensive compared to a hard disk drive and the compact disk. ZIP disks :- are similar to floppy disks, except that they are much faster, and have greater capacity. Network Storage:- is secondary or tertiary storage attached directly to a network which another computer can open copy or read files from. Memory Card and Flash Memory:- that can be used in digital cameras and laptop.
Ports: - The slots into which you plug the cable. The fissure shows different ports at the back of the system unit below.
Bit and Byte:
The information stored in the computer is information or digital signals composed of the symbols are zero and one , which reflected the two cases ( case on / off , or the presence or absence of an electric charge or electrical signal is high and an electrical signal low). The place is capable of storing either the number 0 or 1, we say that he was unable to store and check one or two (1bit) ( 1 B inary Dig it ).
Reflected in the call to take action is called "Binary Digit". Each code system called the check bilateral Binary Digit. "Bit" is the smallest volume derived from B inary Dig it. The Bit clustered in a group composed of 8 cells , called the Byte. Byte of a group of eight binary digits which can be stored by a group of zeros and ones in number eight, the one group called Word , and count the number of bits in a single word on the type of computer, and it has the smallest types of computer word length 8-bit and the largest 128-bit. And lengths of words most commonly used in computers are 32-bit and 64-bit.
Note: the speed of microprocessor mainly on the clock speed and the word size.
Units transform
Bit (b) = ( 0 or 1 )
Byte (B) = 8 bit
Kilobyte (KB) =1024 bytes
Megabyte (MB) = 1,048,576 byte or 1024 KB
Gigabyte ( GB) = 1,073,741,824 byte or 1024 MB
Terabyte (TB) = 1,099,511,627,726 byte or 1024 GB
