Computer Assignment By Ahsan Hussain

By: Ahsan Hussain (MBA) Email: [email protected]

Assignment No. 2 Spring 2009

Random Access Memory Random access memory (usually known by its acronym, RAM) is a form of computer data storage. Today it takes the form of integrated circuits that allows the stored data to be accessed in any order (i.e., at random). The word random thus refers to the fact that any piece of data can be returned in a constant time, regardless of its physical location and whether or not it is related to the previous piece of data. This contrasts with storage mechanisms such as tapes, magnetic discs and optical discs, which rely on the physical movement of the recording medium or a reading head. In these devices, the movement takes longer than the data transfer, and the retrieval time varies depending on the physical location of the next item. The word RAM is mostly associated with volatile types of memory (such as DRAM memory modules), where the information is lost after the power is switched off. However, many other types of memory are RAM as well (i.e., Random Access Memory), including most types of ROM and a kind of flash memory called NOR-Flash.

Random Access Memory (RAM) Functions of RAM RAM is an electronic, or volatile, state. When the computer is off, RAM is empty; when it is on, RAM is capable of receiving and holding a copy of the software instructions and data necessary for processing. The Ram is used for the following purposes:

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By: Ahsan Hussain (MBA) Email: [email protected]

Assignment No. 2 Spring 2009

• Storage of a copy of the main systems program that controls the general operation of the computer. This copy is loaded into RAM when the computer is turn on; it stays there as long as the computer is on. • Temporary storage of a copy of application program instructions to be retrieved by the central processing unit (CPU) for interpretation and execution. • Temporary storage of data that has been input from the keyboard or other input device until instructions call for the data to be transferred into the CPU for processing. • Temporary storage of data that has been produced as a result of processing until instructions call for the data to be used again in subsequent processing or to be transferred to an output device such as the screen, a printer, or a disk storage device. • RAM chips are often called dynamic RAM (DRAM) chips, based on the style of the electric circuits.

Read-only memory Read-only memory (usually known by its acronym, ROM) is a class of storage media used in computers and other electronic devices. Because data stored in ROM cannot be modified (at least not very quickly or easily), it is mainly used to distribute firmware (software that is very closely tied to specific hardware, and unlikely to require frequent updates).

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By: Ahsan Hussain (MBA) Email: [email protected]

Assignment No. 2 Spring 2009

In its strictest sense, ROM refers only to mask ROM (the oldest type of solid state ROM), which is fabricated with the desired data permanently stored in it, and thus can never be modified. However, more modern types such as EPROM and flash EEPROM can be erased and re-programmed multiple times; they are still described as "read-only

memory"(ROM)

because

the

reprogramming

process is generally infrequent, comparatively slow, and often does not permit random access writes to individual memory locations. Despite the simplicity of mask ROM, economies

of

scale

and

field-programmability

often

make

reprogrammable

technologies more flexible and inexpensive, so mask ROM is rarely used in new products as of 2007. Types of ROM PROM, short for programmable read-only memory A PROM is a memory chip on which data can be written only once. Once a program has been written onto a PROM, it remains there forever. Unlike RAM, PROM's retain their contents when the computer is turned off. The difference between a PROM and a ROM (read-only memory) is that a PROM is manufactured as blank memory, whereas a ROM is programmed during the manufacturing process. To write data onto a PROM chip, you need a special device called a PROM programmer or PROM burner. The process of programming a PROM is sometimes called burning the PROM. EPROM (erasable programmable read-only memory) is a special type of PROM that can be erased by exposing it to ultraviolet light. Once it is erased, it can be reprogrammed. An EEPROM is similar to a PROM, but requires only electricity to be erased. EEPROM- Acronym for electrically erasable programmable read-only memory. 3

By: Ahsan Hussain (MBA) Email: [email protected]

Assignment No. 2 Spring 2009

Pronounced double-ee-prom or e-e-prom, an EEPROM is a special type of PROM that can be erased by exposing it to an electrical charge. Like other types of PROM, EEPROM retains its contents even when the power is turned off. Also like other types of ROM, EEPROM is not as fast as RAM. EEPROM is similar to flash memory (sometimes called flash EEPROM). The principal difference is that EEPROM requires data to be written or erased one byte at a time whereas flash memory allows data to be written or erased in blocks. This makes flash memory faster. RAM (Random Access Memory) is a temporary (Volatile) storage area utilized by the CPU. Before a program can be ran the program is loaded into the memory which allows the CPU direct access to the program. Use of ROM for program storage Every stored-program computer requires some form of non-volatile storage to store the initial program that runs when the computer is powered on or otherwise begins execution (a process known as bootstrapping, often abbreviated to "booting" or "booting up"). Likewise, every non-trivial computer requires some form of mutable memory to record changes in its state as it executes. Forms of read-only memory were employed as non-volatile storage for programs in most early stored-program computers, such as ENIAC after 1948 (until then it was not a stored-program computer as every program had to be manually wired into the machine, which could take days to weeks). Read-only memory was simpler to implement since it required only a mechanism to read stored values, and not to change them in-place, and thus could be implemented with very crude electromechanical devices (see historical examples below). With the advent of integrated circuits in the 1960s, both ROM and its mutable counterpart static RAM were implemented as arrays of transistors in silicon chips; however, a ROM memory cell could be implemented using fewer transistors than an SRAM memory cell, since the latter requires a latch (comprising 5-20 transistors) to retain its contents, while a ROM cell might consist of the absence (logical 0) or presence (logical 1) of a single transistor connecting a bit line to a word line. Consequently, ROM could be implemented at a lower cost-per-bit than RAM for many years. 4

By: Ahsan Hussain (MBA) Email: [email protected]

Assignment No. 2 Spring 2009

Most home computers of the 1980s stored a BASIC interpreter or operating system in ROM as other forms of non-volatile storage such as magnetic disk drives were too expensive. For example, the Commodore 64 included 64 KiB of RAM and 20 KiB of ROM contained a BASIC interpreter and the "KERNAL" (sic) of its operating system. Later home or office computers such as the IBM PC XT often included magnetic disk drives, and larger amounts of RAM, allowing them to load their operating systems from disk into RAM, with only a minimal hardware initialization core and boot loader remaining in ROM (known as the BIOS in IBM-compatible computers). This arrangement allowed for a more complex and easily upgradeable operating system. In modern PCs, "ROM" (or Flash) is used to store the basic bootstrapping firmware for the main processor, as well as the various firmware needed to internally control self contained devices such as graphic cards, hard disks, DVD drives, TFT screens, etc, in the system. Today, many of these "read-only" memories – especially the BIOS – are often replaced with Flash memory (see below), to permit in-place reprogramming should the need for a firmware upgrade arise. However, simple and mature sub-systems (such as the keyboard or some communication controllers in the ICs on the main board, for example) may employ mask ROM or OTP (one time programmable). ROM and successor technologies such as Flash are prevalent in embedded systems. This governs everything from industrial robots to appliances and consumer electronics (MP3 players, set-top boxes, etc) all of which are designed for specific functions, but nonetheless based on general-purpose microprocessors in most cases. With software usually tightly coupled to hardware, program changes are rarely needed in such devices (which typically lack devices such as hard disks for reasons of cost, size, and/or power consumption). As of 2008, most products use Flash rather than mask ROM, and many provide some means for connection to a PC for firmware updates; a digital audio player's might be updated to support a new file format for instance. Some hobbyists have taken advantage of this flexibility to reprogram consumer products for new purposes; for example, the iPod Linux and OpenWRT projects have enabled users to run full-featured Linux distributions on their MP3 players and wireless routers, respectively. 5

By: Ahsan Hussain (MBA) Email: [email protected]

Assignment No. 2 Spring 2009

ROM is also useful for binary storage of cryptographic data, as it makes them difficult to replace, which may be desirable in order to enhance information security. ROM for data storage Since ROM (at least in hard-wired mask form) cannot be modified, it is really only suitable for storing data which is not expected to need modification for the life of the device. To that end, ROM has been used in many computers to store look-up tables for the evaluation of mathematical and logical functions (for example, a floating-point unit might tabulate the sine function in order to facilitate faster computation). This was especially effective when CPUs were slow and ROM was cheap compared to RAM. Notably, the display adapters of early personal computers stored tables of bitmapped font characters in ROM. This usually meant that the text display font could not be changed interactively. This was the case for both the CGA and MDA adapters available with the IBM PC XT. The use of ROM to store such small amounts of data has disappeared almost completely in modern general-purpose computers. However, Flash ROM has taken over a new role as a medium for mass storage or secondary storage of files.

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By: Ahsan Hussain (MBA) Email: [email protected]

Assignment No. 2 Spring 2009 F unct

io

nal

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Assignment No. 2 Spring 2009

By: Ahsan Hussain (MBA) Email: [email protected]

Difference: RAM (random access memory) is where programs that are being used currently by the processor to run the program are held. This clears when you lose power or shut down the computer. ROM (read only memory) is where all programs on your computer are stored till needed. This is the hard drive; items stay stored here until you remove them. So when explaining the basics of how this works, use this simple example. Think of the hard drive (ROM) as a file cabinet. It contains all the programs your computer needs to operate. The (RAM) can be described as a desktop. The processor is the worker. So when you open a program, you want to work on .It moves from the filing cabinet, to the desk .This is where all the work is organized and used buy the “worker”. When work on that program is done and you close the program, it’s placed back, into the file cabinet. The same happens when you shut down the system.

Best Printer I Choose For Home use I recently had to get a new printer when my old printer, a Lexmark stopped working. I had it for several years and printed lots of things with it before it stopped working. I was very happy with that Lexmark, so that is why I checked out Lexmark for my new printer. After checking around, I ended up getting a Lexmark z22. The Lexmark z22 is a color jet printer. It is reasonably priced, so it is affordable for people to get for home use. I got mine for about $90 at Wal-Mart. The printer has good quality printing, but people that need a printer for business use may want to get a different printer that is a bit faster in printing speed. The Lexmark z22 is a good choice for people who need a printer for personal use like letters or reports for school, and don't need a super speedy printer.

Lexmark z22

SIZE This

printer

is

very

lightweight and fairly

small so it is a good choice for people with limited space. The Lexmark z22 is smaller 8

By: Ahsan Hussain (MBA) Email: [email protected]

Assignment No. 2 Spring 2009

and lighter than my last Lexmark. It is a light greyish color, the same color most other printers are. DIMENSIONS With the exit tray extended the dimensions of the printer are - 12.6"H x 17.6"W x 19.5"D With the exit tray retracted, the dimensions of the printer are - 6.7"H x 17.6"W x 8.3"D The printer weighs 5.3 pounds. OPERATING PROGRAMS This printer will work with several different operating systems. Windows 95, 98, ME MAC OS 8.6 and 9 Windows XP is not listed, but I am pretty sure the printer will work fine with that version of Windows too. When I got my last Lexmark, I had a computer that was running Windows 95. The drivers that came with the printer were for Windows 95 and Windows NT. When I got a new computer that had Windows 98 on it - the one I am currently using now - the printer worked just fine with it too. I just used the disk for the Windows 95 driver - the drivers were on disks with that printer - and I had no problem using the printer. For the rest of the review, I will be referring to how things are done when the printer is used with Windows since that is what I have. Instructions for use with Macintosh are in the manual. HOOK UP It is very easy to hook this printer up to your computer. The printer can be hooked up to the computer using either a USB or a parallel cable. I used the parallel cable just because I had that from my last printer and I didn't have a USB cable. There is also a power cable to attach to the back of the printer, and then plug into an outlet. MANUAL A user's manual and CD-ROM containing the drives came with the printer. The manual includes instructions for setting up the printer, maintaining the printer, and troubleshooting. The information is covered for Windows and Macintosh. There is also an appendix in the user's manual that covers other information related to the printer. A 9

By: Ahsan Hussain (MBA) Email: [email protected]

Assignment No. 2 Spring 2009

small poster was also included. The poster has illustrations showing how to set up the printer. The user's manual says it is for the Lexmark z22/z32. I saw a picture of the other printer at the Lexmark website when I was looking up some other information. It looks identical to my printer. As far as I can tell, the only difference between the two printers is that the z32 has a slightly faster print speed. SET UP The set up of the Lexmark z22 is easy and takes just a few minutes. Once the printer is hooked up to the computer, you just need to install the drivers. Put the CD in, and the files will start loading. The installation of the files went very fast, even on my older, slower computer. After the installation is finished, the computer may need to be restarted, but I can't remember for sure now it if I had to do that or not. If that step is needed, a little window will pop up saying that the computer must be restarted. All that is left to do is install the ink cartridges, and you'll be off and printing INK CARTRIDGES The Lexmark z22 uses two ink cartridges, one black and one color. If you want to print photographs, there is a photo ink cartridge that is used for those jobs. The printer just holds two cartridges at once, so either the black or the color cartridge is removed and replaced with the photo cartridge when that cartridge is needed. I think the photo cartridge is put in place of the black cartridge for printing photographs, but I'm not completely sure since I haven't done that yet. The cartridges cost about $30 when they need replaced. The black one is usually a few dollars less than the color cartridge. The cartridges can be found at many different stores including stores that sell computers and supplies like Staples, as well as at Wal-Mart. If you check around with different stores, you may be able to save a few dollars when getting the replacement cartridges. INSTALLING THE INK CARTRIDGES To install the ink cartridges, a few steps must be followed. First, the Control Program for the printer must be opened - I'll give some more information on this later in the review too. The Control Program for the printer can be found by going to finding where the Lexmark z22 printer is listed at under the Start menu. The Control Program will be listed there. It will open up a small window. There are five tabs across the top of the 10

By: Ahsan Hussain (MBA) Email: [email protected]

Assignment No. 2 Spring 2009

window. The Status tab will be up when the window opens. That shows how much ink is left in each cartridge, so there is advance warning before the ink is all gone. To install the ink cartridges, click on the Cartridges tab. There are a few options listed here as well. Click on the Install/Change Cartridge button, and follow the instructions. The cartridges have to be removed from their boxes, and the plastic that is around them. There is also a small piece of tape over the bottom of the cartridges that must be removed before the cartridges are installed. The cartridges go in the Print Cartridge Carrier. You just have to push back on the cartridges until you hear a click. After cartridges are installed, they have to be Aligned. That makes sure that everything is printed clearly. Instructions pop up in the window and tell you just what you need to do. It just takes a few minutes. After that is done, the printer is ready to print. PRINTING The sheet feeder on the printer can hold up to 100 sheets of paper, depending on the thickness of the paper. This is a top loading printer, so make sure you get the paper in straight or it will get jammed. Also, if you don't print often, it is a good idea to take the paper out of the printer until you are reading to print again. If the paper is left in the printer for a long time and no printing is done, the edges can curl up, and then when it is time to print, the paper will get jammed up. This happened with my other Lexmark. Taking the paper out of the printer when I wasn't printing took care of that little problem. A small paper guide may need to be adjusted to get the paper loaded right. There are illustrations in the manual that show where the paper guide should be. The Lexmark z22 will also print on envelopes, greeting cards, glossy paper, coated paper, photo paper, banner paper, transparencies, and iron on transfers. Instructions for printing on each of those is included in the manual. When a document is printing, the Control Program will automatically pop up with the Status section showing. If one of the ink cartridges is getting low, you will get a warning about that when the window opens. With my other Lexmark, several pages could still be printed after the warning first happened. The warning would go off before the ink cartridge was completely empty, so you could still do some printing, but you know that you need to get a new one soon. I don't know if this one will set the warning off earlier like that or not since I haven't had to change a cartridge with it yet. The progress of the current print job is displayed. You can cancel the print job here if needed. It shows how 11

By: Ahsan Hussain (MBA) Email: [email protected]

Assignment No. 2 Spring 2009

many copies of the document are printing, how many pages there are in the document, and which page the printer is currently printing. There is a little clock that starts up when a printing job is started. The clock shows how long the job has been printing. RESOLUTION The print resolution in black and in color is up to 1200 x 1200 dpi. SPEED This printer isn't the fastest available, but it is fast enough for me. Businesses that require a lot of printing will want something that is faster. It prints up to 6.5 pages per minute in black and up to 3.5 pages per minute in color. Printing in color especially may take a little longer depending on how detailed the image being printed is. This printer is very quiet when printing. My old Lexmark was a lot louder than this one is. The Lexmark z22 is Energy Star Compliant, so it does not use too much energy. When the page comes out of the printer, the ink is dry. That is good because if you are printing a long document, the pages will pile on top on each other as they come out, and if the ink was still wet, it could smear. I have had this happen to me in the past. I also used a printer once where the ink was smeared when it came out of the printer. PRINTING OPTIONS The printing options can be customized in the Printer Properties dialogue box. When the Paper tab is selected, the size of the paper can be changed and number of copies set. You can also choose to have the document collated or printed in reverse order so that the first page will be on top once printing is complete. There are other options under the Document/Quality tab. Here different paper types can be selected, the dpi can be set, or you can pick to print all in black even if what you are printing has color in it. I use that if I am printing some information from the internet that has a lot of color in it. CONTROL PROGRAM There are five tabs in the Control Program window. I covered the Status earlier. The Options tab has several things you can pick, like having the Control Program close once a print job is done. You can also enable sound effects here. The Cartridges tab is what needs to be selected when an ink cartridge is being changed, aligned, or if the print nozzles need cleaned. You can also find part numbers and order supplies direct from the Lexmark website. If you need to print in DOS, you can set that up under the 12

By: Ahsan Hussain (MBA) Email: [email protected]

Assignment No. 2 Spring 2009

DOS tab. Information about the software version and copyright are found under the ABOUT tab. From the illustrations in the manual, the CONTROL PROGRAM looks different in Macintosh. Overall, I am very happy with my Lexmark z22 printer. It fits my needs perfectly. If you need a good, dependable printer for personal use and don't want to spend a small fortune, this is a great printer. UPDATE In April of 2002, I got a new computer that came with Windows XP,Home Edition installed on the computer. Like I mentioned before, the printer doesn't say that it will work wtih Windows XP, but the printer has worked fine with my new computer. I hooked up the Lexmark z22 when I was setting up my new computer. After I went through a few set up steps, a window popped up saying that Windows XP had detected a new device I can't remember exactly what the window said now, but it was something like that. I was able to click on a button in the window, and XP automatically installed the driver for the Lexmark z22 without me having to put the CD into the CD-Rom drive. Windows XP had the printer set up and ready to print in just a few minutes. It was even faster than the set up process in Windows 98. It did take me through the process of aligning the print heads again. I have printed several things since I got my new computer with no problems. I did have to go in and switch the default printer from the internal fax/modem to the Lexmark z22 so my documents would print, but that just took a few minutes.

Preferred Secondary Storage:Small Computer System Interface, or SCSI (pronounced ['scuzzy][1]), is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, and electrical and optical interfaces. SCSI is most commonly used for hard disks and tape drives, but it can connect a wide range of other devices, including scanners and CD drives. The SCSI standard defines command sets for specific peripheral device types; the presence of "unknown" as one of these types means that in theory it can be used as an interface to almost any device, but the standard is highly pragmatic and addressed toward commercial requirements.

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By: Ahsan Hussain (MBA) Email: [email protected]

•

Assignment No. 2 Spring 2009

SCSI is an intelligent interface: it hides the complexity of physical format. Every device attaches to the SCSI bus in a similar manner.

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SCSI is a peripheral interface: up to 8 or 16 devices can be attached to a single bus. There can be any number of hosts and peripheral devices but there should be at least one host.

•

SCSI is a buffered interface: it uses hand shake signals between devices, SCSI1, SCSI-2 have the option of parity error checking. Starting with SCSI-U160 (part of SCSI-3) all commands and data are error checked by a CRC32 checksum.

•

SCSI is a peer to peer interface: the SCSI protocol defines communication from host to host, host to a peripheral device, peripheral device to a peripheral device. However most peripheral devices are exclusively SCSI targets, incapable of acting as SCSI initiators—unable to initiate SCSI transactions themselves. Therefore peripheral-to-peripheral communications are uncommon, but possible in most SCSI applications. The Symbios Logic 53C810 chip is an example of a PCI host interface that can act as a SCSI target.

SCSI (Small Computer Systems Interface) was designed initially to be a jack-of-alltrades kind of interface. I may repeat some of what has already been said for the sake of making my answer as complete as I can. Reasons To Prefer SCSI Drive 1. SCSI can handle a wide variety of devices: hard drives, scanners, plotters, CD drives, and the list goes on. 2. A SCSI controller can communicate with up to 7 or 15 devices depending on the version. I am sure work is being done to add more. 3. It is often easier to install and setup a SCSI device than with many other device interfaces. (This comment is not limited to the SCSI vs. IDE issue. See Advantage #1 for the scope of what I mean by "device." I also say it is "often easier," not "universally easier.") 4. SCSI controllers and devices are intelligent, they have microcontrollers, if not full blown processors, inside them. They do not require software-base contoller drivers like some Windows devices, putting less load on the CPU.

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By: Ahsan Hussain (MBA) Email: [email protected]

Assignment No. 2 Spring 2009

5. SCSI has proven itself to be a good platform for moving and storing large amounts of data. Recent developments with SCSI have focused on exploiting this feature even further. 6. Newer SCSI devices and controllers are supposed to be backward compatible with older SCSI devices and contollers. (from my own personal experience, this is about 95% true) 7. Recent SCSI contoller and devices currently offer the highest through-put for any peripheral connection scheme currently available. 8. SCSI drives are, on the whole, more reliable than ATA/IDE drives.

Refrences : http://en.wikipedia.org/wiki/RAM http://en.wikipedia.org/wiki/ROM

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