Computer Hard Drive Knowledge

A Computer Hard Drive is a form of Computer memory used to permanently store files and programs. Computer hard Drives can also be referred to as; Hard Disk Drive. When using Microsoft windows a hard disk drive is often referred to as the c-drive. Most PC Hard Drives are stored in a internal drive bay at the front of the computer. Hard drives are connected inside the computer using a ATA, SATA or SCSI cable and a power cord.

There are several types of Hard Drives; some are IDE, SATA and SCSI:

1. IDE Hard Drive: (Also known as an ATA or PATA Hard Drive.) This is one of the most common drives used in computers. You can identify an IDE Hard Drive by having a 40 pin connector and a power connector.
2. SATA Hard Drive: (Also Known as Serial ATA). Very similar to an IDE Hard Drive but uses a higher speed. You can identify an SATA Hard disk by having a smaller power connector than IDE.
3. SCSI Hard Drive: SCSI Hard Drives are faster than IDE and SATA, but are more commonly used in servers due to higher cost. You can identify a SCSI Hard Disk at the connectors. (SCSI uses the same power connector as IDE.

There are four main components to a Hard Drive:

1. Platters: Aluminum, glass, or ceramic dishes coated with magnetic media. These dishes are used to store data and begin to rotate when the computer is turned on.
2. Head Arm: (Also known as a “Actuator Arm”) The Head Arm is similar to the arm on a record player. It allows the Hard Disk Drive to move the read / write heads to the location where the information needs to be read or written to.
3. Chassis: (Also known as the “Case”) A housing that helps protect and organize all components that make up the Hard Disk Drive.
4. Head Actuator: An electronic device controlled by a motor that moves the Head Arm to locations where it is needed.

When looking to buy a hard drive you should be aware of some terms and specifications and what they mean:

Terms:	Example:	Definition:
Brand-	Western Digital	Name of Company supplying HD
Series-	Raptor	Category name within brand of HD
Model-	WD1500ADFD	Model Number of HD
interface-	SATA 1.5Gb/s	Cable connection between computer and HD
Capacity-	150GB	Size of HD storage
RPM-	10000 RPM	Speed at which data is transfered
Cache-	16MB	Small fast memory holding recently accessed data
Average Seek Time-	4.6ms	Time required for read/write heads to switch tracks
Average Latency-	2.99ms	Lapse of time between track switching and data access
Average Write Time-	5.2ms	Total time required to access data needed
Form Factor-	3.5"	Reference to size of disk diameters

Depending on a computers Motherboard setup and options it may be possible to run multiple hard drives. By doing this it is possible to run the drives in a Raid configuration. By running in a Raid configuration you can either have the hard drives working together to form one big hard drive, or they can have the data duplicated from one hard drive to another. By working together they are in a performace setup which allows one hard drive to perform task number one while the next hard disk is already onto task number two. In a duplicated mode each hard drive stores the same exact information so if one hard drive fails all of your information is still stored on the second drive. It is recommended when you replace your hard drive, you get one with more capacity than you would need right now so you will leave expansion room for the future.

Computer RAM Knowledge

Computer RAM is the best known form of memory your computer uses to temporarily store and access data. From the time you turn on your computer, your CPU is constantly using memory (RAM). Every time something is opened or loaded, it gets placed into RAM. This means it is put into a temporary storage area so the CPU can more easily access the information. From there it becomes a continuous cycle where the CPU requests data from

RAM, processes it and then writes new data back to RAM. In most computers, this transfer of data between CPU and RAM happens millions of times every second. When an application is closed, the application itself, along with all its accompanying files is deleted from RAM. This is to make sure there is room for new data, so unless the changed files are saved to a permanent storage device, they will be lost.

Types of Computer RAM RAM Type: Pins: Usage: SDRAM 168 Typically only used in older and slower computers. RDRAM 184 Only used in certain Pentium 4’s with certain Intel chipsets. DDR 184 Faster version of SD RAM used in Pentium 4’s and Athlon DDR2 240 Newer version of DDR RAM with higher clock frequencies DDR3 240 Newer version of DDR2 with higher clock frequencies

Upgrading Computer RAM

When looking to upgrade your computer’s RAM, you will find RAM information typically displayed like this:

1GB, 240-pin DIMM, DDR2 PC2-5300,

• 1GB refers to the size of the memory
• 240-pin refers to the number of pins used to connect to the motherboard
• DIMM- Dual In-line Memory Module
• SIMM- Single In-line Memory Module
• DDR2 refers to the type of memory
• PC2-5300 refers to the module type

Some other pieces of information you might find in a RAM description are:

• Clock frequency-refers to speed of the RAM in MHz (800MHz)
• CAS (Column Address Strobe) Latency-refers to the number of clock cycles that elapse from the   time the request for data is sent to the actual memory location until the data is transmitted from the  module. This is represented by a set of 4 numbers also known as RAM timing (4-4-4-12). These numbers stand for:
• TCL - CAS Latency Time
• Trcd - DRAM RAS# to CAS# Delay
• Trp - DRAM RAS# Precharge
• Tras - Precharge delay

Normally the BIOS will allow a user to adjust RAM timing to increase performance and stability.

Computer RAM

RAM is considered the most critical component in a computer system. Every bit of data must pass through RAM to get to the processor. Generic, low-cost RAM is most often the cause of data corruption and program crashes, so never skimp on the quality of RAM when upgrading. Make sure the RAM you choose is considered Grade A. Grade A RAM can only be found through major manufacturers, such as: Crucial.com.

Basic Computer Operations

How Computers Work

Input: Information and programs are entered into the computer through Input devices such as the keyboard, disks, or through other computers via network connections or modems connected to the Internet. The input device also retrieves information off disks.

Output: Output Devices displays information on the screen (monitor) or the printer and sends information to other computers. They also display messages about what errors may have occurred and brings up message or dialog box asking for more information to be input. The output device also saves information on the disk for future use.

Processing: The CPU or central processing unit is sometimes called the Control Unit and directs the operation of the input and output devices. The Coprocessor or the Arithmetic-Logic Unit does arithmetic and comparisons. The memory or RAM temporarily stores information (files and programs) while you are using or working on them. The BIOS or basic input/output system controls the dialogue between the various devices.
Keyboard Layout and Data Entry

ENTER or RETURN - Moves the cursor down one line and to the left margin. Enter also process commands such as choosing an option in a dialog (message) boxes and submitting a form.

DEL or DELETE - Deletes the character at cursor and/or characters to the right of the cursor and all highlighted (or selected) text.

BKSP or BACKSPACE - Deletes the character to the left of cursor and all hightlighted text.

SPACE BAR - Moves the cursor one space at a time to the right

SHIFT KEY - Use the shift keys to type capital letters and to type the upper character on keys with two characters on them

CAPS LOCK - Locks the keyboard so it types capital letters (a light goes on when caps lock is on)

TAB - Moves the cursor five spaces to the right (number of spaces are usually adjustable). Tab moves to the next field in a form or table (Shift-Tab for previous field).

ESC or ESCAPE - Cancels a menu or dialog box

ARROW KEYS - Moves the cursor around document without changing text

FUNCTION KEYS or F KEYS - Access commands by themselves or in combination with the three command keys; CTRL, SHIFT, and ALT

Keyboard


Command or Special Keys

Command keys normally do nothing on their own but work in combination with other keys. Each piece of software uses the command keys differently though there is a move to standardize some functions. The Control key or Ctrl is often used to access commands. The Alternative key or Alt is often used to access menus. The Shift key is used to type CAPITAL LETTERS. As well the command keys are all used to move through documents and edit text faster and easier. As well many computers have Special keys design specifically for the particular computer. Apple computers have the Apple keys and Macs have Command keys. Many keyboards now have a Windows key specifically for Windows 9x and newer systems. Many older computers also have special keys used for a variety of different functions.

Some Notebook or Laptop keys are left out because of space limitations and they usually have a Special function key which allows other keys to double for the missing ones.
Basic Typing Rules

Place one space between each word, after a punctuation mark and at the end of a sentence. Always start a sentence with a capital letter. Use capitals for names, addresses, provinces and countries, places, organizations, businesses, associations, schools, colleges, universities, days of the week, months, holidays, nationalities, ethnic groups and languages.

Learning the keyboard is the first step to learning computers. Learning involves practice. It really is as simple as that. There are two kinds of typing.

The first is called Touch Typing. The Touch Typist uses the Home Keys (asdf for the left hand and jkl; for the right) and all the fingers on both hands as well as the thumbs for the Space Bar while typing. There are many commercial and public domain programs that are designed to teach this method.

The other method is some times called 'Hunt and Peck' or depending on finger strength 'Search and Destroy'. This involves using one or more fingers on one or two hands to type. It is a perfectly acceptable way of using a computer and many people get along fine with this technique.