Audio

• Speakers and headphones are the primary audio output devices for a PC.
  
• Some monitors have speakers built into their sides. Other speakers are free standing.
  
• Passive speakers plug into and are powered directly from the output signal provided by the 'speaker out' port on the sound card.
  
• Active speakers amplify the sound signal from the sound card using battery or rectified AC house power. 

Mouse

The mouse is the most common 'pointing device' used in PCs. Every mouse has two buttons and most have one or two scroll wheels. 

Keyboard

• The keyboard was the first input device developed for the PC.
  
• The standard keyboard layout provides 104 keys organized as four groups:
  
  
  • alphanumeric keys (A-Z, 0-9) 
  • location keys (home, end etc.) 
  • numeric keypad 
  • function keys (F1-F12)

Compact Disk Drive

• The CDD installs in one of the external 5-1/4 inch drive bays in the front of the PC case. It is secured by machine screws. Some manufacturers offer special rail-like systems that mount on the CDD. These allow the drive to be removed from the PC without having to remove any screws.

Floppy Disk Drive

• The FDD installs in one of the external drive bays at the front of the PC case and is secured by machine screws. External means you can access the drive from the outside.
  
• It is powered by a cable with a 4-pin connector that comes from the power supply. 

Digital Video Disk drive

1. DVD also known as the Digital Versatile Disk drive, installs in one of the external 5 1/4 inch drive bays in the PC. It is secured by machine screws. Some manufacturers offer special rail-like systems that mount on the DVD. These allow the drive to be removed from the PC without having to remove screws.
   
2. It is designed to optically access data stored on a DVD. A laser moves back and forth near the disk surface and accesses data at a very fast rate.
   
3. A 4-pin cable from the power supply plugs into the CDD and provides power to it.
   
4. Data between the DVD drive and the motherboard is carried on a 40-pin IDE (Integrated Drive Electronics) cable.
   
5. There are two types of DVD drives that typically go into PCs.
   
   
   • DVD-ROM (Read Only Memory) can read DVDs and CDs and costs about $75.
     
   • DVD-RAM (Random Access Memory) units can read and write DVDs. They can also read CDs and cost about $500.
   
   
6. A standard DVD stores up to 4.7 Gbytes on one side of the disk. Digitally formatted movies can be stored on a standard DVD in MPEG-2 format.

Monitor

CRT Monitors 

• Up until recently, CRTs (Cathode RayTubes) were the only type of displays for use with desktop PCs. They are relatively big (14" to 16" deep) and heavy (over 15 lbs). 

Power Supply

• A power supply is installed in the back corner of the PC case, next to the motherboard.
  
• It converts 120vac (standard house power) into DC voltages that are used by other components in the PC.
  
• A 20 conductor cable carries +5vdc, -5vdc +12vdc, -12vdc and ground to the motherboard.
  
• Another pair of cables, each with four conductors and two 4-pin connectors daisy-chained along it, carry +5vdc, +12vdc and ground to the drives (hard, floppy and CD/DVD).
  
• Typical PC power supplies are rated at 200-250 watts and sell for about $50 - $75. Higher wattage supplies are available.

Motherboard

The motherboard is the main circuit board in a PC. It contains all the circuits and components that run the PC. 

Major Components found on the motherboard are: 

• CPU - the Central Processing Unit is often an Intel Pentium or Celeron processor. It is the heart of every PC. All scheduling, computation and control occurs here.
• BIOS - Basic Input Output System is a non-volatile memory that contains configuration information about the PC. It contains all the code required for the CPU to communicate with the keyboard, mouse video display, disk drives and communications devices.

USB

Short for Universal Serial Bus, USB is a standard that was introduced in 1995 by Intel, Compaq, Microsoft and several other computer companies. USB 1.x is an external bus standard that supports data transfer rates of 12 Mbps and is capable of supporting up to 127 peripheral devices. In the picture to the right, is an example of a USB cable being connected into the USB port.
USB 2.0, also known as hi-speed USB, was developed by Compaq, Hewlett Packard, Intel, Lucent, Microsoft, NECand Philips and was introduced in 2001. Hi-speed USB is capable of supporting a transfer rate of up to 480 Mbps and is backwards compatible, meaning it is capable of supporting USB 1.0 and 1.1 devices and cables.

What are the differences between hardware and software?

Computer hardware is any physical device, something that you are able to touch and software is a collection of instructions and code installed into the computer and cannot be touched. For example, the computer monitor you are using to read this text on and the mouse you are using to navigate this web page is computer hardware. The Internet browser that allowed you to visit this page and the operating system that the browser is running on is software.

Choosing a hard drive for your desktop computer

Hard Disk Drive (HDD) options can be quite bewildering for a computer system assembler. Even though there are only two major desktop hard drive brands available in Pakistan there is a lot of confusion among new system builders about what HDD to choose.

The two brands available in Pakistan are Seagate and Western Digital (WD).  Seagate and WD 3.5″ internal HDDs are divided into three categories:

Green Drives: These are drives that consume less power than other models. They are marketed as environmentally friendly drives and sold under the Western Digital Green Caviar and Seagate Barracuda Green/LP labels. To save power the Seagate Barracuda Green drives operate at 5900RPM while the WD drives have a variable RPM around the 5400 mark.

HDDs in general don’t really consume a lot of power so the savings to be had with the green drives are negligible. But the lower RPM means that the green drives are significantly slower than other hard drives. The WD Green Caviar are among the worst in this regard.

Mainstream Drives: The Seagate Barracuda 7200.xx (xx denotes drive generation) and the Western Digital Blue Caviar are the two brands used in this category. Both are 7200 RPM drives that provide good performance for everyday desktop usage.

Performance Drives: Seagate performance oriented drives are branded the Barracuda XT but they are not widely available in Pakistan. Western Digital Black drives are the only ones in this category that are available here. These are 7200RPM drives which have an access time a few ms less than the mainstream drives. The prices are also higher by about a few thousand rupees.

Recommendation

For the typical Pakistani consumer the Seagate Barracuda 7200.xx or the Western Digital Caviar Blue are the best hard drives. The Green drives are the ones to avoid at all cost and the WD Blacks are not worth the price premium. Regardless of which brand or model you choose make sure you buy from a reputable dealer.

SATA 2 vs. SATA 3

Serial ATA or SATA has become the standard interface between storage devices and computer motherboards. SATA continues to be updated to faster standards such as SATA 3.