Chapter 4

                                                                    Chapter4


. The system unit is a box-like case housing the electronic components of a computer that are used to process data. ex: - Drive bay
                            - Power supply
                            - Sound card
                            - Video card
                            - Processor
                            - Memory.
. Motherboard : a printed circuit board containing the principal components of a computer or other device, with connectors into which other circuit boards can be slotted.
. Processor: is the logic circuitry that responds to and processes the basic instructions that drive a computer. The term processor has generally replaced the term central processing unit (CPU).Then we have processor , input ,and storage device are connected to memory ,and then from memory to output. let say the processor contains registers ,that temporarily hold data and in
. Control unit is a component of a computer's central processing unit (CPU) that directs operation of the processor.
. Arithmetic logic unit : a unit in a computer that carries out arithmetic and logical operations.
. System clock controls the timing all computer operations.
. The pace of the system clock :the operating speed of a computer or its microprocessor, defined as the rate at which it performs internal operations and expressed in cycles per second (megahertz).
. The leading manufacturers of personal computer processor chips are intel and AMD .
. Processor chip generates heat that could the chip to burn up.
. Parallel processing :a mode of computer operation in which a process is split into parts that execute simultaneously on different processors attached to the same computer.
 Data representation
. Analog signals are continuous and very in strength and quality. Digital signals are one in of two states on and off.
. ASCII  is the most common format for text files in computers and on the Internet. In an ASCII file, each alphabetic, numeric, or special character is represented with a 7-bit binary number.
Memory
. Memory is any physical device capable of storing information temporarily or permanently, and the stores three parts.
.Two types of memory: RAM and ROM.
  1. RAM has three type: Dynamic RAM, Static RAM, Magnetoresistive RAM.         
. Ram chip  are the computer's temporary workspace, while flash memory chips are used like disk drives, and then its necessary in a computer often depends on the software.
.Memory cache  also called CPU memory, is random access memory (RAM) that a computer microprocessor can access more quickly than it can access regular RAM.

2. ROM is a type of storage medium that permanently stores data on personal computers (PCs) and other electronic devices.
. PROM: permanent memory chip in which the content is created (programmed) by the customer rather than by the chip manufacturer.
. Flash memory can be erased electronically and rewritten.
- CMOS technology provides high speeds and consumes little power.
- Access time is the time taken to retrieve data from storage and are measured  in nanoseconds.
Expansion slots and Adapters card
. An expansion slot is a socket on the motherboard that can hold an adapter card .An adapter card enhances functions of a component of the system unit (sound card and video card).
.With plug and play , the computer automatically can configure adapter cards and other peripherals as you install them.
Ports and Connectors
.Port is the point at which a peripheral attaches to or communicates with a system unit. on the notebook computers the ports are on the back ,front ,or sides. and others types :firewire port, Bluethooth port etc..
.Connectors joins a cable to a port .
. USB  is a plug-and-play portable storage device that uses flash memory and is lightweight enough to attach to a keychain.
. Port replicator is an external device that provides connections to peripherals through ports built into the device.
. Docking station is an external device that attaches to a mobile computer or device.
. Bus allows the various devices both inside and attached to the system unit to communication with each other -data bus and address bus.
. Word size is the number of bits the processor can interpret and execute at a given time.
. Bay  is an open section on the computer used for expansion for add-ons to your computer, such as a hard drive and CD-rom drive .
- Drive bay typically holds drives.
- Power supply is an internal hardware component that supplies components in a computer with power. The power supply converts a volt alternating current (AC) into a steady low-voltage direct current (DC) usable by the computer and rated by the number of watts it generates.