| kilobyte (kB) | 103 | 210 |
| megabyte(MB) | 106 | 220 |
| gigabyte (GB) | 109 | 230 |
| terabyte (TB) | 1012 | 240 |
| petabyte (PB) | 1015 | 250 |
| exabyte (EB) | 1018 | 260 |
| zettabyte (ZB) | 1021 | 270 |
| yottabyte (YB) | 1024 | 280 |
Thursday, April 1, 2010
Computer Data
Friday, February 19, 2010
Optical basics
Optical Terminology
Optical fiber - 3 components, Core, Cladding, Coating
Fiber types - MM (Multi Mode), SM (Single Mode) (Generally SM is yellow color cable and MM is orange color cable)
Data is sent as light pulses through the optical cable.
Conventional optical networks wave lengths - 850nm, 1310nm, 1550nm.
Light source
WDM - Wavelength Division Multiplexing.
DWDM - Dense Wavelength Division Multiplexing
In DWDM space between channels(wavelengths) is less, so needs good light source to send good signal.
DWDM uses expensive powerful lasers.
DWDM is used for long distance transmissions.
CWDM - Coarse Wavelength Division Multiplexing
In CWDM channels are spaced widely.
oesn't need powerful laser.
Used for shorter/medium distances
OADM - Optical Add Drop Multiplexers.
EDFA - Erbium Doped Fiber Amplifier (used in DWDM to Amplify the signal)
Connectors
Cable Connector type - (SC, LC are widely used)
| SM | - Single Mode fiber. |
| MM | - Multi Mode fiber. |
| WDM | - Wave length Division Multiplexing. |
| DWDM | - Dense Wavelength Division Multiplexing. |
| CWDM | - Coarse Wavelength Division Multiplexing. |
| OADM | - Optical Add Drop Multiplexers. |
| EDFA | - Erbium Doped Fiber Amplifier. |
| GBIC | - Giga Bit Interface Converter. |
| SFP | - Small Form-factor Pluggable). |
| O-E-O | - Optical-Electrical-Optical. |
| FC | - Fiber Channel. |
| OSNR | - Optical Signal to Noise Ratio |
Optical fiber - 3 components, Core, Cladding, Coating
Fiber types - MM (Multi Mode), SM (Single Mode) (Generally SM is yellow color cable and MM is orange color cable)
Data is sent as light pulses through the optical cable.
Conventional optical networks wave lengths - 850nm, 1310nm, 1550nm.
Light source
- 850nm uses LED (Cheap, short distance)
- 1310nm uses LED or laser (Cheap, medium distance)
- 1550nm uses High quality laser(Expensive .
WDM - Wavelength Division Multiplexing.
DWDM - Dense Wavelength Division Multiplexing
In DWDM space between channels(wavelengths) is less, so needs good light source to send good signal.
DWDM uses expensive powerful lasers.
DWDM is used for long distance transmissions.
CWDM - Coarse Wavelength Division Multiplexing
In CWDM channels are spaced widely.
oesn't need powerful laser.
Used for shorter/medium distances
OADM - Optical Add Drop Multiplexers.
EDFA - Erbium Doped Fiber Amplifier (used in DWDM to Amplify the signal)
Connectors
- GBIC - Giga Bit Interface Converter
- SFP - Small Form-factor Pluggable) - upto 4.25 Gbits/s
- XFP - 10 gig support for dieerent protocols
- SFP+ - 10 gig Ethernet and 8 gig FC, modified/updated XFP (SFP+ is small size, low power consumption, less expensive) .
Cable Connector type - (SC, LC are widely used)
Saturday, February 13, 2010
Virtual PDF printer
When you are not connected to printer and if you have webpage/coupon which can be printed only once the you need a virtual PDF printer. After installation virtual pdf printer will install a printer.
Just click print in the browser and select the virtual printer, this will create pdf file.
You can use this application to create pdf files from any application which has print option.
Some of the virtual pdf printer applications are mentioned below
bullzip (Freeware) - http://www.bullzip.com/products/pdf/info.php#download
win2pdf - Free (Free version adds a extra page at the end of the pdf document)
http://www.win2pdf.com/
Just click print in the browser and select the virtual printer, this will create pdf file.
You can use this application to create pdf files from any application which has print option.
Some of the virtual pdf printer applications are mentioned below
bullzip (Freeware) - http://www.bullzip.com/products/pdf/info.php#download
win2pdf - Free (Free version adds a extra page at the end of the pdf document)
http://www.win2pdf.com/
Friday, November 6, 2009
Basic application software install on clean OS install
If you do clean install of windows and want to install all the basic software required, instead of downloading all software and installing them one by one, go to http://ninite.com/ select the software you want and download the installer. Run the installer, it will install all the selected software on your PC. This is much faster than individual download and install.
Wednesday, January 28, 2009
GSM phones
GSM (Global System for Mobile communications) operate in 4 frequencies.
850, 900, 1800, 1900 MHz
If a phone is quad band phone, it supports all 4 frequencies. so it works any where in the world.
If it is not quad band phone we need to check what frequencies the phone supports and check if the operators in the area where you are planning to use the phone operates in that frequencies.
Suppose if you have a tri band phone which operates in 850/1800/1900, the phone doesnt works with operators that use 900 frequency.
In US ATT operates with both 850 and 1900 frequencies and T-Mobile operates at 1900.
In India Airtel, BSNL, IDEA operates at 900 frequency and Vodafone, Reliance, tata indicom operates at 1800 frequency.
If you take a tri band phone with 850/1800/1900 phone which worked in US with ATT or T-mobile, In india this phone works only with Vodafone, Reliance, tata indicom. it doesnt works with Airtel, BSNL, IDEA.
check the below link for more information on frequencies operated by various service provides in different countries.
http://www.gsmworld.com/roaming/gsminfo/index.shtml
850, 900, 1800, 1900 MHz
If a phone is quad band phone, it supports all 4 frequencies. so it works any where in the world.
If it is not quad band phone we need to check what frequencies the phone supports and check if the operators in the area where you are planning to use the phone operates in that frequencies.
Suppose if you have a tri band phone which operates in 850/1800/1900, the phone doesnt works with operators that use 900 frequency.
In US ATT operates with both 850 and 1900 frequencies and T-Mobile operates at 1900.
In India Airtel, BSNL, IDEA operates at 900 frequency and Vodafone, Reliance, tata indicom operates at 1800 frequency.
If you take a tri band phone with 850/1800/1900 phone which worked in US with ATT or T-mobile, In india this phone works only with Vodafone, Reliance, tata indicom. it doesnt works with Airtel, BSNL, IDEA.
check the below link for more information on frequencies operated by various service provides in different countries.
http://www.gsmworld.com/roaming/gsminfo/index.shtml
Wednesday, December 3, 2008
Freeware
List of Best Freeware by category is found in below link
http://www.techsupportalert.com/pc-tools.html
http://www.techsupportalert.com/pc-tools.html
Monday, November 17, 2008
Flash Memory - 1
Flash memory is non-volatile memory, which means that no power is needed to maintain the information stored in the chip.
Technology:
It is a specific type of EEPROM (Electrically Erasable Programmable Read-Only Memory) .
It comes in NAND and NOR types. NOR-type has long erase and write times, but provides full address and data buses, allowing random access to any memory location. while NAND-type has faster erase and write times, and requires a smaller chip area per cell, (thus allowing greater storage densities and lower costs per bit than NOR flash). it also has up to ten times the endurance of NOR flash. However, the I/O interface of NAND flash does not provide a random-access external address bus.
NOR type flash is for faster read access (can be used where ROM is required), NAND type is used for storage (can replace hard drives, CD, DVD etc).
Advantages:
Unlike in hard drives theres no moving part in flash memory, so it requires less power, and more shock resistance. so flash is becoming more popular in portable devices.
less latencies compared to hard drive.
Limitations:
1. with flash memory is it has a finite number of erase-write cycles.
2. limited capacity compared to hard drives
but the number of cycles, capacity increases with technology improvements.
Transfer Rates:
Commonly advertised is the maximum read speed. it is represented in "x" format or MB/s
1x is equal to 150 kilobytes per second.
So a 100x memory card goes to 150 KB x 100 = 15000 KB per second = 14.65 MB per second.
Flash memory comes in different types, capacities, shapes and sizes.
different companies makes them in different varieties. below are list
of popular flash memory types.
Compact Flash
Memory stick
1. standard (50 mm x 21.5 mm x 2.8 mm),
2. Duo(31 mm x 20 mm x 1.6 mm),
3. Pro Duo(31 mm x 20 mm x 1.6 mm)
4. Micro(15 mm x 12.5 mm x 1.2 mm)
SD, mini SD, micro SD, SDHC
SDHC extension to SD, it has capacities exceeding 2GB
SDHC has speed class rating
class 2 - 2MB/s
class 4 - 4MB/s
class 6 - 6MB/s
xD (standard, type M, type H)
Thin and small (20 mm × 25 mm × 1.78 mm)
USB (no standard size, comes in various sizes and capacities)
Technology:
It is a specific type of EEPROM (Electrically Erasable Programmable Read-Only Memory) .
It comes in NAND and NOR types. NOR-type has long erase and write times, but provides full address and data buses, allowing random access to any memory location. while NAND-type has faster erase and write times, and requires a smaller chip area per cell, (thus allowing greater storage densities and lower costs per bit than NOR flash). it also has up to ten times the endurance of NOR flash. However, the I/O interface of NAND flash does not provide a random-access external address bus.
NOR type flash is for faster read access (can be used where ROM is required), NAND type is used for storage (can replace hard drives, CD, DVD etc).
Advantages:
Unlike in hard drives theres no moving part in flash memory, so it requires less power, and more shock resistance. so flash is becoming more popular in portable devices.
less latencies compared to hard drive.
Limitations:
1. with flash memory is it has a finite number of erase-write cycles.
2. limited capacity compared to hard drives
but the number of cycles, capacity increases with technology improvements.
Transfer Rates:
Commonly advertised is the maximum read speed. it is represented in "x" format or MB/s
1x is equal to 150 kilobytes per second.
So a 100x memory card goes to 150 KB x 100 = 15000 KB per second = 14.65 MB per second.
--------------------------
Rating Speed (MB/s)
-------------------------
6x 0.9
32x 4.8
40x 6.0
66x 10.0
100x 15.0
133x 20.0
150x 22.5
200x 30.0
-----------------------
Flash memory comes in different types, capacities, shapes and sizes.
different companies makes them in different varieties. below are list
of popular flash memory types.
- Compact flash from sandisk
- Memory Stick from sony/sandisk
- Secure digital (SD) from panasonic, toshiba, sandisk
- xD from olympus, fujifilm
- USB flash drives from various manufactures, and Universally compatible across all computer platforms using USB 1.1/2.0
Compact Flash
 | |
Memory stick
1. standard (50 mm x 21.5 mm x 2.8 mm),
2. Duo(31 mm x 20 mm x 1.6 mm),
3. Pro Duo(31 mm x 20 mm x 1.6 mm)
4. Micro(15 mm x 12.5 mm x 1.2 mm)
1 2 3 4
  |  |  |  |
SD, mini SD, micro SD, SDHC
SDHC extension to SD, it has capacities exceeding 2GB
SDHC has speed class rating
class 2 - 2MB/s
class 4 - 4MB/s
class 6 - 6MB/s
xD (standard, type M, type H)
Thin and small (20 mm × 25 mm × 1.78 mm)
 |  |  |
USB (no standard size, comes in various sizes and capacities)
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