In computing, a scanner is a Input device that analyzes & captures an image (such as a photograph, printed text, or handwriting) or an object (such as an ornament) from the source documents into the Computer system and converts it to a digital image. Scanner facilitates the capturing information in graphical as well in editable format. The graphical images thus scanned can be seen and processed directly by the computer.
Two types of scanner are CONTACT and LASER. Most scanners today are variations of the desktop (or flatbed) scanner. The flatbed scanner is the most common in offices.
Hand-held scanner is the laser scanner, where the device is moved by hand. The main purpose of using hand-held scanner is for quickly capturing text.
Hand-held scanner is that, which moves across the image to be scanned by hand. They are small and less expensive than their desktop counterparts, but rely on the dexterity of the user to move the unit across the paper. Trays are available that keep the scanner moving in a straight line.
Handheld scanners are a convenient way to get printed text into an editable format on your computer, but the best devices are prohibitively expensive.
Hand scanners are manual devices, which are dragged across the surface of the image to be scanned. Scanning documents in this manner requires a steady hand, as an uneven scanning rate would produce distorted images. They typically have a "start" button which is held by the user for the duration of the scan, some switches to set the optical resolution, and a roller which generates a clock pulse for synchronization with the computer. A typical hand scanner also had a small window through which the document being scanned could be viewed.
Handheld scanners have scan heads 4-5 inches wide, which makes them very portable. They plug into parallel port so they're easy to share among people and can be a good addition to laptop.
You can get cheap handheld scanners for under $150, but their declining popularity might make them hard to find. Another kind of handheld scanner is the pen scanner. You drag a pen scanner over a line of print like a highlighter. The built-in optical recognition software turns the scan into text, which can be transferred in to a computer via serial or USB port. Handheld Barcode scanners are also well known & in use for reading barcode of the items in a most of the shopping centers.
In case of some advanced Hand-held scanners for e.g Wizcom Handheld scanner, the device can "see" text and automatically activate the scanner when text comes into its field of view. Then, you only have to roll the pen smoothly over the line you want to capture and lift it off the page at the end of the text line. The optical character recognition (OCR) engine then translates the scanned images into editable text.
Handheld scanners use the same basic technology as a flatbed scanner, but rely on the user to move them instead of a motorized belt. It is briefly popular but is now not used due to the difficulty of obtaining a high-quality image.
Tuesday, July 8, 2008
The purpose of hand-held scanner
In computing, a scanner is a Input device that analyzes & captures an image (such as a photograph, printed text, or handwriting) or an object (such as an ornament) from the source documents into the Computer system and converts it to a digital image. Scanner facilitates the capturing information in graphical as well in editable format. The graphical images thus scanned can be seen and processed directly by the computer.
Two types of scanner are CONTACT and LASER. Most scanners today are variations of the desktop (or flatbed) scanner. The flatbed scanner is the most common in offices.
Hand-held scanner is the laser scanner, where the device is moved by hand. The main purpose of using hand-held scanner is for quickly capturing text.
Hand-held scanner is that, which moves across the image to be scanned by hand. They are small and less expensive than their desktop counterparts, but rely on the dexterity of the user to move the unit across the paper. Trays are available that keep the scanner moving in a straight line.
Handheld scanners are a convenient way to get printed text into an editable format on your computer, but the best devices are prohibitively expensive.
Hand scanners are manual devices, which are dragged across the surface of the image to be scanned. Scanning documents in this manner requires a steady hand, as an uneven scanning rate would produce distorted images. They typically have a "start" button which is held by the user for the duration of the scan, some switches to set the optical resolution, and a roller which generates a clock pulse for synchronization with the computer. A typical hand scanner also had a small window through which the document being scanned could be viewed.
Handheld scanners have scan heads 4-5 inches wide, which makes them very portable. They plug into parallel port so they're easy to share among people and can be a good addition to laptop.
You can get cheap handheld scanners for under $150, but their declining popularity might make them hard to find. Another kind of handheld scanner is the pen scanner. You drag a pen scanner over a line of print like a highlighter. The built-in optical recognition software turns the scan into text, which can be transferred in to a computer via serial or USB port. Handheld Barcode scanners are also well known & in use for reading barcode of the items in a most of the shopping centers.
In case of some advanced Hand-held scanners for e.g Wizcom Handheld scanner, the device can "see" text and automatically activate the scanner when text comes into its field of view. Then, you only have to roll the pen smoothly over the line you want to capture and lift it off the page at the end of the text line. The optical character recognition (OCR) engine then translates the scanned images into editable text.
Handheld scanners use the same basic technology as a flatbed scanner, but rely on the user to move them instead of a motorized belt. It is briefly popular but is now not used due to the difficulty of obtaining a high-quality image.
Two types of scanner are CONTACT and LASER. Most scanners today are variations of the desktop (or flatbed) scanner. The flatbed scanner is the most common in offices.
Hand-held scanner is the laser scanner, where the device is moved by hand. The main purpose of using hand-held scanner is for quickly capturing text.
Hand-held scanner is that, which moves across the image to be scanned by hand. They are small and less expensive than their desktop counterparts, but rely on the dexterity of the user to move the unit across the paper. Trays are available that keep the scanner moving in a straight line.
Handheld scanners are a convenient way to get printed text into an editable format on your computer, but the best devices are prohibitively expensive.
Hand scanners are manual devices, which are dragged across the surface of the image to be scanned. Scanning documents in this manner requires a steady hand, as an uneven scanning rate would produce distorted images. They typically have a "start" button which is held by the user for the duration of the scan, some switches to set the optical resolution, and a roller which generates a clock pulse for synchronization with the computer. A typical hand scanner also had a small window through which the document being scanned could be viewed.
Handheld scanners have scan heads 4-5 inches wide, which makes them very portable. They plug into parallel port so they're easy to share among people and can be a good addition to laptop.
You can get cheap handheld scanners for under $150, but their declining popularity might make them hard to find. Another kind of handheld scanner is the pen scanner. You drag a pen scanner over a line of print like a highlighter. The built-in optical recognition software turns the scan into text, which can be transferred in to a computer via serial or USB port. Handheld Barcode scanners are also well known & in use for reading barcode of the items in a most of the shopping centers.
In case of some advanced Hand-held scanners for e.g Wizcom Handheld scanner, the device can "see" text and automatically activate the scanner when text comes into its field of view. Then, you only have to roll the pen smoothly over the line you want to capture and lift it off the page at the end of the text line. The optical character recognition (OCR) engine then translates the scanned images into editable text.
Handheld scanners use the same basic technology as a flatbed scanner, but rely on the user to move them instead of a motorized belt. It is briefly popular but is now not used due to the difficulty of obtaining a high-quality image.
Sunday, July 6, 2008
Losing to big sister Venus little solace for Serena
WIMBLEDON, England -- Serena Williams hates to lose.
This is not a well-kept secret.
Her attitude after a big defeat confirms it. A lioness who survives to hunt each opponent as prey, Serena's competitive heart just doesn't compute allowances for failure.
Even her family confirms, the concept of being checkmated is the bane of Serena's existence. In fact, her relatives willingly take much of the blame for her inability to deal with defeat as an outgrowth of them always spoiling her as the baby of the family. Her sister, Lyndrea, who flew in from Los Angeles yesterday, said Serena to this day can't even bear to lose when they play the card game "spoons."
"Serena thinks everything is supposed to go her way, that's the bottom line," said mom/coach Oracene Price, who had finally removed the large sunglasses she hid behind during the match. "She thinks that's the way it's supposed to go in life. But this is life."
Serena's face in disappointment always tells the story -- it's a sour frown, one of anger and disbelief that anyone, even her sister Venus, would have the goods to one better her in a match. And that's the look we all were treated to when Venus solidified her position as the pre-eminent grass-court player of her generation with a fifth Wimbledon title, a title that came at the expense of Serena in an entertaining 7-5, 6-4 victory on Saturday afternoon.
CARL DE SOUZA/Getty Images
Serena Williams let her frustration show during Saturday's final as her chance at another Wimbledon title -- and another win over her big sister Venus in a Grand Slam final -- slipped away."It's definitely not any easier," said Serena, about coming up short in a Grand Slam final to kin instead of a nonrelated rival. "I just look at her as another opponent at the end of the day. I don't think it's harder, but it's definitely not easier."
To drive home the point of how unacceptable a loss is to Serena, it can be noted that while she gave Venus credit for her abilities on grass, she managed to insert herself into the explanatory equation. And let's remember when pondering the comment, Venus has five Wimbledon titles and Serena has only two, although she did win her two with final victories over Venus in 2002 and '03.
"Well, it says a lot about her. I mean, she's won five Wimbledons now," Serena said. "She's beaten me on grass now, so that definitely says a lot."
It should be made clear that being a bit of a sore loser does not mean that Serena exhibits unsportsmanlike behavior. The fact that she conceded a game point in the ninth game of the first set to Venus during the final after umpire Carlos Ramos called for them to replay the point, is a testament to her fairness in battle.
Certainly, Serena's passion for competition and success supports her future candidacy as one of the all-time greats of the game. She's already won eight Grand Slam titles, at least one at each of the four majors, dating back to her first as a 17-year-old at the 1999 U.S. Open. She's captured 31 career titles to date and is a former world No. 1. And she's only 26, so there's plenty more opportunity ahead.
For her mother's part, however, she believes it's time for Serena to grow up and experience a reality check on life in the real world.
"Well, you know, she's going to have to learn how to suck things up," Price said. "[She needs to] say, 'OK, I'm not going to win everything. This is going to make me a better person. This will build character for myself and I have to learn how to lose. I might not be happy about it, but I just have to go on, go on and say, you know what, I didn't get this one, but I'm getting the next one.'"
While Price compassionately understands Serena's disappointment in being outplayed, she would prefer her daughter to deal with defeat in a different way -- her present style of going AWOL is disturbing. Most recently, Serena tuned out after her shocking third-round exit at the recent French Open, in which unlike Saturday's final, she played sloppy, dispassionate tennis.
"I'm not going to say nothing," said Price, smiling when asked how she might go about consoling Serena. "Before she won Australia [2007] that time and she lost in Hobart I didn't see her for two days. She didn't answer my e-mails, no texts, nothing. And when she lost at the French Open [2008], which was the worst, nothing for a week or two. You can't talk to her because she's not communicating with anyone."
It wasn't all gloom and doom for Serena, as it turned out on Saturday.
About three hours after she failed to win a ninth Grand Slam title against big sis, the two walked back onto Centre Court together, a joint force to be reckoned with, winning the women's doubles championships 6-2, 6-2 over Lisa Raymond and Samantha Stosur. For Venus, that marked the second time at Wimbledon she scored a daily double by taking the singles and doubles title -- she also performed that magic in 2000. For Serena, it salvaged the day, because she would not go home without a 2008 Wimbledon trophy.
But everyone knew the day was all about their earlier encounter, a match that produced terrific tennis, surprisingly, considering the blustery conditions. It was a competitive affair played to a capacity crowd.
The meetings between Venus and Serena now stand at 8-8 with Serena leading 5-2 in Grand Slam final outings. And while Venus tried to contain her joy in victory so as to not rub it into Serena's face, Serena did not hesitate to hide her frustration in failure.
If those details don't squelch the crazy notion that the Williams family has made a habit of fixing the matches between Venus and Serena, it's hard to imagine what would silence that incessant chatter, which Venus so aptly deemed "offensive" and "extremely disrespectful" in advance of the final.
This is not a well-kept secret.
Her attitude after a big defeat confirms it. A lioness who survives to hunt each opponent as prey, Serena's competitive heart just doesn't compute allowances for failure.
Even her family confirms, the concept of being checkmated is the bane of Serena's existence. In fact, her relatives willingly take much of the blame for her inability to deal with defeat as an outgrowth of them always spoiling her as the baby of the family. Her sister, Lyndrea, who flew in from Los Angeles yesterday, said Serena to this day can't even bear to lose when they play the card game "spoons."
"Serena thinks everything is supposed to go her way, that's the bottom line," said mom/coach Oracene Price, who had finally removed the large sunglasses she hid behind during the match. "She thinks that's the way it's supposed to go in life. But this is life."
Serena's face in disappointment always tells the story -- it's a sour frown, one of anger and disbelief that anyone, even her sister Venus, would have the goods to one better her in a match. And that's the look we all were treated to when Venus solidified her position as the pre-eminent grass-court player of her generation with a fifth Wimbledon title, a title that came at the expense of Serena in an entertaining 7-5, 6-4 victory on Saturday afternoon.
CARL DE SOUZA/Getty Images
Serena Williams let her frustration show during Saturday's final as her chance at another Wimbledon title -- and another win over her big sister Venus in a Grand Slam final -- slipped away."It's definitely not any easier," said Serena, about coming up short in a Grand Slam final to kin instead of a nonrelated rival. "I just look at her as another opponent at the end of the day. I don't think it's harder, but it's definitely not easier."
To drive home the point of how unacceptable a loss is to Serena, it can be noted that while she gave Venus credit for her abilities on grass, she managed to insert herself into the explanatory equation. And let's remember when pondering the comment, Venus has five Wimbledon titles and Serena has only two, although she did win her two with final victories over Venus in 2002 and '03.
"Well, it says a lot about her. I mean, she's won five Wimbledons now," Serena said. "She's beaten me on grass now, so that definitely says a lot."
It should be made clear that being a bit of a sore loser does not mean that Serena exhibits unsportsmanlike behavior. The fact that she conceded a game point in the ninth game of the first set to Venus during the final after umpire Carlos Ramos called for them to replay the point, is a testament to her fairness in battle.
Certainly, Serena's passion for competition and success supports her future candidacy as one of the all-time greats of the game. She's already won eight Grand Slam titles, at least one at each of the four majors, dating back to her first as a 17-year-old at the 1999 U.S. Open. She's captured 31 career titles to date and is a former world No. 1. And she's only 26, so there's plenty more opportunity ahead.
For her mother's part, however, she believes it's time for Serena to grow up and experience a reality check on life in the real world.
"Well, you know, she's going to have to learn how to suck things up," Price said. "[She needs to] say, 'OK, I'm not going to win everything. This is going to make me a better person. This will build character for myself and I have to learn how to lose. I might not be happy about it, but I just have to go on, go on and say, you know what, I didn't get this one, but I'm getting the next one.'"
While Price compassionately understands Serena's disappointment in being outplayed, she would prefer her daughter to deal with defeat in a different way -- her present style of going AWOL is disturbing. Most recently, Serena tuned out after her shocking third-round exit at the recent French Open, in which unlike Saturday's final, she played sloppy, dispassionate tennis.
"I'm not going to say nothing," said Price, smiling when asked how she might go about consoling Serena. "Before she won Australia [2007] that time and she lost in Hobart I didn't see her for two days. She didn't answer my e-mails, no texts, nothing. And when she lost at the French Open [2008], which was the worst, nothing for a week or two. You can't talk to her because she's not communicating with anyone."
It wasn't all gloom and doom for Serena, as it turned out on Saturday.
About three hours after she failed to win a ninth Grand Slam title against big sis, the two walked back onto Centre Court together, a joint force to be reckoned with, winning the women's doubles championships 6-2, 6-2 over Lisa Raymond and Samantha Stosur. For Venus, that marked the second time at Wimbledon she scored a daily double by taking the singles and doubles title -- she also performed that magic in 2000. For Serena, it salvaged the day, because she would not go home without a 2008 Wimbledon trophy.
But everyone knew the day was all about their earlier encounter, a match that produced terrific tennis, surprisingly, considering the blustery conditions. It was a competitive affair played to a capacity crowd.
The meetings between Venus and Serena now stand at 8-8 with Serena leading 5-2 in Grand Slam final outings. And while Venus tried to contain her joy in victory so as to not rub it into Serena's face, Serena did not hesitate to hide her frustration in failure.
If those details don't squelch the crazy notion that the Williams family has made a habit of fixing the matches between Venus and Serena, it's hard to imagine what would silence that incessant chatter, which Venus so aptly deemed "offensive" and "extremely disrespectful" in advance of the final.
Friday, July 4, 2008
Find out the storage capacity of a magnetic disk having 80 tracks, 15 sectors per track and storing 512 bytes per
Magnetic disks are direct-access medium and so are the most popular online secondary storage devices. Direct-access devices are also called random-access devices because information is literally available at random or in any order. Access to any location on the device is direct and so approximately equal access time is required for each location. An example of this is a music CD where if you wish to listen to the 5th song, you can directly select the 5th track. It does not require you to fast forward the previous 4 songs.
Magnetic disk is a circular plate made of metal or plastic, coated with magnetized material. Often both sides of the disk are used. Data is recorded on the disk in the form of magnetised and non-magnetised spots (not visible to the naked eye).
Track: Data is stored in concentric rings or tracks. To minimize the interference of magnetic fields, the adjacent tracks are separated by inter track gaps.
Sector: Tracks are commonly divided into sections called sectors. In most systems, the minimum quantity of information that can be transferred is a sector. Usually 8 or more sectors per track are found.
Usually the upper surface of the topmost disk and the lower surface of the bottom-most disk are not used since these are prone to getting scratched easily. For faster access of data from disk packs, a concept called cylinders is used.
Disk Storage Capacity
Capacity: Maximum number of bits that can be stored
Vendors express capacity in units of gigabytes (GB), where 1 GB = 10^9.
Capacity is determined by these technology factors: Capacity is determined by these technology factors:
Recording density (bits/in): number of bits that can be squeezed into a 1 inch segment of a track.
Track density (tracks/in): number of tracks that can be squeezed into a 1 inch radial segment.
Arial density (bits/in2): product of recording and track density.
The storage capacity of a disk system can be determined as follows:
Storage capacity = Number of recording surfaces x Number of tracks per surface x
Number of sectors per track x Number of bytes per sector
In this question we have given a Magnetic disk having 80 tracks having 15 sectors per track. Also, each sector can store 512 bytes, then
Storage capacity = 2 sides per disk x 80 tracks per side x
15 sectors per track x 512 bytes per sector
= 1,228,800 bytes
= Approximately 1.23 MB
Magnetic disk is a circular plate made of metal or plastic, coated with magnetized material. Often both sides of the disk are used. Data is recorded on the disk in the form of magnetised and non-magnetised spots (not visible to the naked eye).
Track: Data is stored in concentric rings or tracks. To minimize the interference of magnetic fields, the adjacent tracks are separated by inter track gaps.
Sector: Tracks are commonly divided into sections called sectors. In most systems, the minimum quantity of information that can be transferred is a sector. Usually 8 or more sectors per track are found.
Usually the upper surface of the topmost disk and the lower surface of the bottom-most disk are not used since these are prone to getting scratched easily. For faster access of data from disk packs, a concept called cylinders is used.
Disk Storage Capacity
Capacity: Maximum number of bits that can be stored
Vendors express capacity in units of gigabytes (GB), where 1 GB = 10^9.
Capacity is determined by these technology factors: Capacity is determined by these technology factors:
Recording density (bits/in): number of bits that can be squeezed into a 1 inch segment of a track.
Track density (tracks/in): number of tracks that can be squeezed into a 1 inch radial segment.
Arial density (bits/in2): product of recording and track density.
The storage capacity of a disk system can be determined as follows:
Storage capacity = Number of recording surfaces x Number of tracks per surface x
Number of sectors per track x Number of bytes per sector
In this question we have given a Magnetic disk having 80 tracks having 15 sectors per track. Also, each sector can store 512 bytes, then
Storage capacity = 2 sides per disk x 80 tracks per side x
15 sectors per track x 512 bytes per sector
= 1,228,800 bytes
= Approximately 1.23 MB
Wednesday, July 2, 2008
Seek Time & Memory Hierarchy
¬ SEEK TIME
The disk address is specified in terms of the surface number, track or cylinder number, and the sector number. The read/write heads need to be first positioned on the track on which the data are to be recorded or from which data needs to be read.
Information is always written from the beginning of a sector and can be read only from the beginning of the desired track. Thus, the disk access time depends on the (i) Seek Time & (ii) Latency Time
Seek time: The seek time measures the amount of time required for the read/write heads to move between tracks over the surfaces of the platters. Seek time is one of the most commonly discussed metrics for hard disks, and it is one of the most important positioning performance specifications. The seek time would vary depending upon the position of the access arms at the time the read/write command was received, i.e., if the access arm was positioned on the outermost track and the current read operation required it to be positioned on the 5th track, then the time taken to position the access arm on track 5 is the seek time. It is obvious from this example that moving from outermost to the innermost track or vice versa would result in the maximum seek time. The average seek time in most systems is 10-100 milliseconds.
Typical full seek time is 8 ms. Average seek time (from one random position to another random position) is 1/3 full seek time.
While seek time is usually given as a single number, in fact there are three different seek time specifications you should examine for a drive, as they represent the drive's performance when doing different types of seeks:
(i) Average: As discussed, this is meant to represent an average seek time from one random track (cylinder) to any other. This is the most common seek time metric, and is usually 8 to 10 ms, though older drives had much higher numbers, and top-of-the-line SCSI drives are now down to as low as 4 ms!
(ii) Track-to-Track: This is the amount of time that is required to seek between adjacent tracks. This is similar in concept (but not exactly the same as) the track switch time and is usually around 1 ms.
(iii) Full Stroke: This number is the amount of time to seek the entire width of the disk, from the innermost track to the outermost. This is of course the largest number, typically being in the 15 to 20 ms range. In some ways, combining this number with the average seek time represents the way the drive will behave when it is close to being full.
MEMORY HIERARCHY:
Memory in the computer system is required for storage and subsequent retrieval of instructions and data. Fast access to instructions and data stored in memory is essential in order to meet the throughput requirements of the processor. Memory system can be considered to consist of three groups of memories:
Ø Internal processor memory consists of a small set of high-speed registers
Ø Primary storage or main memory is a large memory, which is fast, but not as fast as internal processor memory.
Ø Secondary storage or auxiliary memory or backing store is much larger in size than the main memory but is slower than the main memory.
A balanced provision for different kinds of memory – CD-ROM, hard-disc, DVD, main semiconductor memory (DRAM), cache memory (SRAM, SSRAM or SDRAM), processor registers – is necessary in order to meet the performance/cost requirements of a computer system.
650 MB – 1 TB, 100 ms - ??
The total memory capacity of the computer can therefore be visualised as being a hierarchy of components consisting of all storage devices employed in a computer system from the slow but high-capacity auxiliary memory to a relatively faster main memory, to an even smaller and faster cache memory accessible to the high-speed processing logic. Thus, as one goes up in the hierarchy, the following conditions occur:
(i) Decreasing cost per bit (ii) Increasing capacity (iii)Increasing access time
(iv) Decreasing frequency of access of the memory by the processor
CPU Registers:
CPU contains several registers for storing data and instructions. But these can store only few bytes. Internal processor memory consists of a small set of high-speed registers that are internal to a processor and are used as temporary locations where actual processing is done.
Main Memory:
Primary storage or main memory is a large memory, which is fast, but not as fast as internal processor memory. This memory communicates directly with the CPU and is mainly based on integrated circuits.
Cache Memory:
Another kind of memory that is increasingly being used in modem computers is called the cache memory. Cache memories are small, fast memories placed between the CPU and the main memory. Due to it’s expensiveness of this memory it is used in small quantities only. The memory read or writes operation is first checked with the cache and if the desired data is available in the cache it is used by the CPU directly.
Secondary Storage Memory:
Devices that provide backup storage (like magnetic tapes and disks) are called secondary storage or auxiliary memory. It typically stores all the system programs and other software.
For e.g. CD-ROM, hard-disc, DVD
The disk address is specified in terms of the surface number, track or cylinder number, and the sector number. The read/write heads need to be first positioned on the track on which the data are to be recorded or from which data needs to be read.
Information is always written from the beginning of a sector and can be read only from the beginning of the desired track. Thus, the disk access time depends on the (i) Seek Time & (ii) Latency Time
Seek time: The seek time measures the amount of time required for the read/write heads to move between tracks over the surfaces of the platters. Seek time is one of the most commonly discussed metrics for hard disks, and it is one of the most important positioning performance specifications. The seek time would vary depending upon the position of the access arms at the time the read/write command was received, i.e., if the access arm was positioned on the outermost track and the current read operation required it to be positioned on the 5th track, then the time taken to position the access arm on track 5 is the seek time. It is obvious from this example that moving from outermost to the innermost track or vice versa would result in the maximum seek time. The average seek time in most systems is 10-100 milliseconds.
Typical full seek time is 8 ms. Average seek time (from one random position to another random position) is 1/3 full seek time.
While seek time is usually given as a single number, in fact there are three different seek time specifications you should examine for a drive, as they represent the drive's performance when doing different types of seeks:
(i) Average: As discussed, this is meant to represent an average seek time from one random track (cylinder) to any other. This is the most common seek time metric, and is usually 8 to 10 ms, though older drives had much higher numbers, and top-of-the-line SCSI drives are now down to as low as 4 ms!
(ii) Track-to-Track: This is the amount of time that is required to seek between adjacent tracks. This is similar in concept (but not exactly the same as) the track switch time and is usually around 1 ms.
(iii) Full Stroke: This number is the amount of time to seek the entire width of the disk, from the innermost track to the outermost. This is of course the largest number, typically being in the 15 to 20 ms range. In some ways, combining this number with the average seek time represents the way the drive will behave when it is close to being full.
MEMORY HIERARCHY:
Memory in the computer system is required for storage and subsequent retrieval of instructions and data. Fast access to instructions and data stored in memory is essential in order to meet the throughput requirements of the processor. Memory system can be considered to consist of three groups of memories:
Ø Internal processor memory consists of a small set of high-speed registers
Ø Primary storage or main memory is a large memory, which is fast, but not as fast as internal processor memory.
Ø Secondary storage or auxiliary memory or backing store is much larger in size than the main memory but is slower than the main memory.
A balanced provision for different kinds of memory – CD-ROM, hard-disc, DVD, main semiconductor memory (DRAM), cache memory (SRAM, SSRAM or SDRAM), processor registers – is necessary in order to meet the performance/cost requirements of a computer system.
650 MB – 1 TB, 100 ms - ??
The total memory capacity of the computer can therefore be visualised as being a hierarchy of components consisting of all storage devices employed in a computer system from the slow but high-capacity auxiliary memory to a relatively faster main memory, to an even smaller and faster cache memory accessible to the high-speed processing logic. Thus, as one goes up in the hierarchy, the following conditions occur:
(i) Decreasing cost per bit (ii) Increasing capacity (iii)Increasing access time
(iv) Decreasing frequency of access of the memory by the processor
CPU Registers:
CPU contains several registers for storing data and instructions. But these can store only few bytes. Internal processor memory consists of a small set of high-speed registers that are internal to a processor and are used as temporary locations where actual processing is done.
Main Memory:
Primary storage or main memory is a large memory, which is fast, but not as fast as internal processor memory. This memory communicates directly with the CPU and is mainly based on integrated circuits.
Cache Memory:
Another kind of memory that is increasingly being used in modem computers is called the cache memory. Cache memories are small, fast memories placed between the CPU and the main memory. Due to it’s expensiveness of this memory it is used in small quantities only. The memory read or writes operation is first checked with the cache and if the desired data is available in the cache it is used by the CPU directly.
Secondary Storage Memory:
Devices that provide backup storage (like magnetic tapes and disks) are called secondary storage or auxiliary memory. It typically stores all the system programs and other software.
For e.g. CD-ROM, hard-disc, DVD
Tuesday, July 1, 2008
Chopper crash leaves grieving mother-to-be Expectant father among 6 to die when medical helicopters collide in Ariz.
FLAGSTAFF, Ariz. - A soon-to-be father who loved being a firefighter was among six people killed when two medical helicopters collided in Arizona.
Michael MacDonald, 26, was fighting wildfires at the Grand Canyon when he was bitten by an insect on Friday and taken to a nearby hospital, said Tyson Runningwolf, fire management officer for the Blackfeet Nation in Montana.
MacDonald suffered prophylactics shock — a life-threatening allergic reaction — from the treatment he received for the bite, and was being transported to the Flagstaff Medical Center in Arizona when the helicopters collided Sunday afternoon.
One of the helicopters was operated by Air Methods from Englewood, Colo., and the other was from Classic Helicopters of Woods Cross, Utah. Both aircraft were Bell 407 models.
Investigators plan to begin examining the remains of the helicopters on Tuesday.
Ninth accident this year
It was the ninth accident this year involving emergency medical aircraft, bringing the number of deaths to 16, National Transportation Safety Board officials said Monday.
MacDonald was aboard the chopper coming from the South Rim of the Grand Canyon, about 70 air miles from Flagstaff, farther by ground. The drive on well-paved roads takes about 90 minutes. The other chopper was coming from Winslow, about 50 miles away on Interstate 40.
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Three people died on each of the two Bell 407 helicopters: the pilot, the patient and a flight nurse on one chopper, the pilot, the patient and a paramedic on the other. A flight nurse on one of the helicopters was hospitalized in critical condition.
At the crash site Monday, wreckage from one helicopter sits as a pile of twisted metal among bent pine trees. One long rotor blade sticks up in the air, while another is bent up at a 90-degree angle. Green wire hangs out of the wreckage, and medical bags are strewn about. The smell of fuel lingered Monday.
More than 300 feet away, what was a helicopter is now a pile of burned metal in a clearing atop a mesa.
A surveillance camera from one of the hospital's parking lots captured the crash, but it will require technical work to remove the time stamp that blocks footage of the collision.
MacDonald was a "super nice kid" who loved being a firefighter, said his uncle, John Lee Hall, of Browning, Mont. He grew up on the Blackfeet Indian Reservation, but had been living in Missoula and attending the University of Montana as a physical education major. He enjoyed playing basketball in his free time, Hall said.
Monday, June 30, 2008
John talks up faithfulness, heart and firm feet; plus, the latest on Madonna & Guy, Jen & Ben, Brad & Angelina, Britney, Justin, Mary-Kate and many mo
John Mayer isn't exactly keeping his bologna hole closed when it comes to his romance with Jennifer Aniston, even if his responses require a bit of reading between the lines.
In a sit-down with USA Today to plug his newly launched tour and live CD/DVD, "Where the Light Is," he handily turns a direct question about his A-list honey of two months into a statement of self-affirmation.
"All I can tell you is that I have made every decision in my life with complete authenticity," pronounces the crooner. "My feet are firmly on the ground. If you do things from the heart, it feels awesome."
Mayer also mentions that he's happy to be back on tour and supporting "the message that I'm a musician, because there's been a lot of periphery lately."
Some well-toned, perfectly coiffed, paparazzi-hounded periphery.
"I don't have a problem with my privacy as much as I have a problem with people messing with my message," he explains. "If you're going to take pictures of me doing mundane stuff, will you at least take pictures of me playing guitar? Because right now it looks like all I do is drink coffee and do dry cleaning and go eat dinner."
Still, if the "Goonies"-loving chatterbox hopes to shift the focus back onto his pop ditties, perhaps he should suggest that Aniston keep her distance while he's on the road.
Jen looks perky after winging to Europe, while John still seems in need of some caffeine outside an Amsterdam coffee shop.
The Los Angeles Times reports she rendezvoused with Mayer earlier this week in Amsterdam, where he was performing, and he was supposedly spied exiting her hotel Tuesday morning.
The actress, who may or may not tag along on John's tour dates in England this week, did manage to squeeze in some work while she was in the pot-tolerant town, attending a press conference to promote her forthcoming doggie-centric flick, "Marley & Me."
But the gab-fest was strictly business, says the paper, with reporters under strict orders not to ask Aniston or leading man Owen Wilson any questions about their private lives.
Mayer, on the other hand, doesn't mind getting personal, at least about certain things.
"I've never cheated on anybody, so you won't have anybody coming out the woodwork saying that I have," the former flame of Jessica Simpson, Cameron Diaz and Jennifer Love Hewitt declares to the London Telegraph. "Instead of worrying about career damage, I've dated women."
Heck, he even shares his head-scratchingly successful wooing technique.
"All I've ever done was decided that I fancied somebody, and said, 'Would you like to go out and get a meal somewhere?' And done so in a social setting, where other people can see you," expounds Mayer. "And then maybe, 'Would you like to go have another meal?' Maybe did that a few times."
He also reveals his method for extricating himself from a romance that isn't working out: "And then, when I realized that I didn't wanna wrong anybody by continuing, said, 'I'd rather be a great friend to you than a bad boyfriend.' I swear to God, I have a really good track record!"
That stance is seemingly confirmed by a nugget in the New York Post, which claims he gave sometime squeeze Minka Kelly a buzz to let her know his romance with Aniston was about to go public.
"Minka received a call from John prior to the story breaking about his relationship with Jennifer," a snitch tattles to the paper. "He apologized to Minka, 'Sorry, but I'm really in love.'"
The spy says the "Friday Night Lights" starlet found it funny (as in strange, not ha-ha), because "during his relationship with her, John mentioned, 'I don't really get this Jennifer Aniston thing.'"
Meanwhile, Mayer also wants you to know he's not only a nice guy to date -- he's fun to hang out with.
"I think I'm a good beer-buddy," he asserts to the Telegraph. "The only people I rub up wrong are the people who think I shouldn't be having this good a time, the people who go, 'No one man should be that happy.'"
One person Mayer has apparently rubbed the right way is Aniston's pal David Arquette, who channels Tony the Tiger when asked about the lovebirds, telling Us, "They're great!"
In a sit-down with USA Today to plug his newly launched tour and live CD/DVD, "Where the Light Is," he handily turns a direct question about his A-list honey of two months into a statement of self-affirmation.
"All I can tell you is that I have made every decision in my life with complete authenticity," pronounces the crooner. "My feet are firmly on the ground. If you do things from the heart, it feels awesome."
Mayer also mentions that he's happy to be back on tour and supporting "the message that I'm a musician, because there's been a lot of periphery lately."
Some well-toned, perfectly coiffed, paparazzi-hounded periphery.
"I don't have a problem with my privacy as much as I have a problem with people messing with my message," he explains. "If you're going to take pictures of me doing mundane stuff, will you at least take pictures of me playing guitar? Because right now it looks like all I do is drink coffee and do dry cleaning and go eat dinner."
Still, if the "Goonies"-loving chatterbox hopes to shift the focus back onto his pop ditties, perhaps he should suggest that Aniston keep her distance while he's on the road.
Jen looks perky after winging to Europe, while John still seems in need of some caffeine outside an Amsterdam coffee shop.
The Los Angeles Times reports she rendezvoused with Mayer earlier this week in Amsterdam, where he was performing, and he was supposedly spied exiting her hotel Tuesday morning.
The actress, who may or may not tag along on John's tour dates in England this week, did manage to squeeze in some work while she was in the pot-tolerant town, attending a press conference to promote her forthcoming doggie-centric flick, "Marley & Me."
But the gab-fest was strictly business, says the paper, with reporters under strict orders not to ask Aniston or leading man Owen Wilson any questions about their private lives.
Mayer, on the other hand, doesn't mind getting personal, at least about certain things.
"I've never cheated on anybody, so you won't have anybody coming out the woodwork saying that I have," the former flame of Jessica Simpson, Cameron Diaz and Jennifer Love Hewitt declares to the London Telegraph. "Instead of worrying about career damage, I've dated women."
Heck, he even shares his head-scratchingly successful wooing technique.
"All I've ever done was decided that I fancied somebody, and said, 'Would you like to go out and get a meal somewhere?' And done so in a social setting, where other people can see you," expounds Mayer. "And then maybe, 'Would you like to go have another meal?' Maybe did that a few times."
He also reveals his method for extricating himself from a romance that isn't working out: "And then, when I realized that I didn't wanna wrong anybody by continuing, said, 'I'd rather be a great friend to you than a bad boyfriend.' I swear to God, I have a really good track record!"
That stance is seemingly confirmed by a nugget in the New York Post, which claims he gave sometime squeeze Minka Kelly a buzz to let her know his romance with Aniston was about to go public.
"Minka received a call from John prior to the story breaking about his relationship with Jennifer," a snitch tattles to the paper. "He apologized to Minka, 'Sorry, but I'm really in love.'"
The spy says the "Friday Night Lights" starlet found it funny (as in strange, not ha-ha), because "during his relationship with her, John mentioned, 'I don't really get this Jennifer Aniston thing.'"
Meanwhile, Mayer also wants you to know he's not only a nice guy to date -- he's fun to hang out with.
"I think I'm a good beer-buddy," he asserts to the Telegraph. "The only people I rub up wrong are the people who think I shouldn't be having this good a time, the people who go, 'No one man should be that happy.'"
One person Mayer has apparently rubbed the right way is Aniston's pal David Arquette, who channels Tony the Tiger when asked about the lovebirds, telling Us, "They're great!"
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