This Document contains the following sections:

	Background on: Hardware
	Elements of Personal Computing Hardware
	Categories of Computer
	Networking and the Internet
	Index of Other Pages and Supplemental Materials on: Hardware

Background on:

This discussion of hardware will focus on the personal computer architecture, which is similar to the architectures of all computers from mainframe to palm-computers. Sections describing hardware components of:

	Personal Computers
	Communication Basics with links to describe telecommunications and data communications
	Local Area Networks
	Multimedia
	Chronology of Events in the History of Microcomputers

Elements of Personal Computing Hardware

the central controlling unit of a computer system. The CPU contains the

	Arithmetic--Logic Unit (ALU) which executes instructions, Main Memory which is used to hold data and instructions that are being processed, and other components. The ALU can add, subtract, and compare numbers. Multiplication is repetitive addition; division is repetitive subtraction, etc.
	Control Unit - reads stored programs, one instruction at a time, and directs other components of the computer system to perform required tasks.
	The control unit contains registers (memory locations) that both manipulate or compare data and keep track of where the instructions being executed and stored in primary memory.

Because the CPU operates must faster that disk drives and other secondary storage devices, for efficiency, before data can be processed it must reside in Primary memory. From primary memory data and program code can be obtained by the ALU and processed. Primary memory can be purchased in the form of ROM (Read Only Memory) a permanent memory, RAM (Random Access Memory) a volatile memory, SIMM, DIMM.

	BIOS is a permanent (Read Only Memory or ROM) that contains the initial boot program used when the computer is first turned on.
	A volatile (Random Access Memory or RAM) types whose variants include SIMM and DIMM
	is used as the primary interface between the CPU and slower secondary storage and peripheral devices.
	Cache Memory a high speed memory used as an intermediate storage area used to facilitate the access of primary memory by the CPU. The access speed of primary memory needs to be at least as fast as the CPU can access the memory, but fast primary memory is expensive. In general, the primary memory used in most systems is slower than the CPU access rate. Faster cache memory is used to speed up the CPU's access of memory.
	Disk Caching, similar in principle to the memory caching, but instead of using high-speed SRAM, a disk cache uses conventional main memory. In disk caching, the most recently accessed data from the disk (as well as adjacent sectors) is stored in a memory buffer (the memory cache). When a program needs to access data from the disk, it first checks the disk cache to see if the data is there. Disk caching can dramatically improve the performance of applications, because accessing a byte of data in RAM can be thousands of times faster than accessing a byte on a secondary storage device.

non-volatile data storage (retains data even when power is off.) The most common types of secondary storage are:

	Magnetic Tape (low cost, serial access)
	Magnetic Disk (including RAID or Redundant Array of Inexpensive Disks
	Optical Disk (CD-ROM)
	Redundant Array of Inexpensive Disks (RAID)

The motherboard is a place the processor is connected to the rest of the system. On the motherboard is located the CPU, main memory (and cache), and card slots into which peripheral interface cards can be inserted. Considerations include:

	Chip Set -- the pacemaker of the computer system. Chip sets control the memory I/O, the bus I/O, interrupt requests (IRQ - when a peripheral needs to communicate with the system), and Direct Memory Access requests (DMA - a way of offloading from the CPU the work of moving from main memory to secondary memory.)
	BIOS (Basic Input/Output System) -- the code typically located on permanent memory that on startup runs a power-on test, self-test, etc. Originally called a bootstrap program, newer versions will need to support Windows95 Plug-and-Play feature.

The transfer of data between main memory and sources outside the CPU is called input/output (I/O). Original PCs used either serial or parallel interface cards to control individual devices.  Because of a limited number of IRQs used to address devices, many computers now include an I./O Bus architecture.   Examples of input/output devices include:

	Video Display Terminals (VDT)
	Mouse
	Keyboard
	Point of Sale Terminals
	Bar Code Reader

Requirements for data communication include:

	Access to a communication channel, either a Local Area Network (LAN) or a Dialup type telephone circuit.
	Communication Interface Device to convert computer data to a format used by the communication channel, either a Network Interface Card to connect to a LAN, a Modem to connect to an analog telephone circuit, or other type devise as required by the communication channel being used (ex. small routers are sometimes used when connecting to the Internet using digital communication channels).
	for Networks, a client version of the Network Operating System will need to be running on the local computer. Computers connecting to the Internet use the TCP/IP network protocol.

Communication may employ either a Point-to-Point or networked method using either a Circuit Switching or Packet Switching architecture using either Dialup or Leased Line communication channels.