What exactly is computer memory and how is it used?

Memory is one of the core hardware components for the computer. It is the component that temporarily stores information (such as Numbers, Characters, Settings, Instructions, Files and so on) once a computer has started. The information is temporary because when a computer is switched off or restarted the information is deleted from memory. When a program has finished with the information, the memory it was using is released (not deleted) so other programs can then use that memory.

Memory itself is a microchip (see above) that can temporarily store Bytes. The more bytes the memory has the more information it can temporarily store. A byte is just a number with a value between 0 and 255. It is a program’s job to turn each byte into something a human and/or another program can interpret. For example. If the memory was storing 4 Bytes with the values 74, 79, 72 and 78 it would mean nothing to you. However. To Microsoft Word 2007 the byte value 74 means J. The byte value 79 means O. The byte value 72 means H and the byte value 78 means N. So even though the memory is storing byte values that mean nothing to you, Microsoft Word 2007 has no trouble interpreting (reading) those same byte values as JOHN. The same applies to other programs that interpret (read) the byte values. For example. A Paint program might interpret 74 as colour Red, 79 as colour Yellow, 72 as colour Blue and 78 as colour Green. Whereas a Language program might interpret (read) 74 as English, 79 as Spanish, 72 as French and 78 as Italian. It depends on the program. Either way, the memory will always see 74, 79, 72 and 78. Here is a diagram of the memory with the 4 Bytes interpreted.

The logic behind interpreting byte values is like so: If the byte value is 74 display J (Microsoft Word 2007). If the byte value is 74 use English (Language program). If the byte value is 74 use colour Red (Paint program). And so on. In other words, the byte will always have its value of 74 but it can be interpreted differently depending on the program doing the interpreting. Programs that save settings files use interpretation a lot to cut down on the number of bytes used. For example. If a paint program had to interpret RED, YELLOW and BLUE with characters it would use 13 Bytes (R E D Y E L L O W B L U E). Whereas using the logic of byte values to represent RED, YELLOW and GREEN it would only use 3 Bytes (79, 74 and 72).

Although the above concentrated on programs interpreting byte values that were already stored inside memory, the reverse is just as true. For example. When you type the word JOHN into a Microsoft Word 2007 document its stores (puts) the byte values 74, 79, 72 and 78 inside memory. The same with a paint program. Instead of storing the characters R E D (byte values 82, 69 and 68) it might store the byte value 74 (which represents RED in the above example) so that it is uses 1 Byte, instead of 3, every time you use the red ink.

Basically, memory is just full of numbers that are interpreted by programs to mean Instructions, Settings, Characters, Words, Sentences, Numbers, Symbols and so on.

ENOUGH MEMORY
 
When a program opens it first allocates some memory for its own needs. For example. If you open a 1000 bytes essay file with Microsoft Word 2007, from a floppy disk, and edit it (i.e you change the word JOHN into PAUL) the changes are not made to the essay file on the floppy disk. They are made inside memory instead, to avoid wear of the floppy disk. If you imagine every time you edited an essay character (byte value) the whole essay file had to be re-saved onto floppy disk you would soon end up with a damaged floppy disk. Just changing JOHN into PAUL would mean four re-saves. Memory is purposely made for the constant editing of byte values.

When Microsoft Word 2007 opens an essay file from floppy disk for example it first allocates (reserves) 1000 bytes of file memory, so it can store an exact copy of the essay file inside that memory – The original essay file on the floppy disk is left intact. The next thing Microsoft Word 2007 does is allocate some memory for its editing needs. For example. If you make a copy of the word JOHN, because you want to add (paste) it somewhere else in the essay, behind the scenes Microsoft Word 2007 makes a copy of the word JOHN by storing the word JOHN inside the edit memory. So you now have 1000 bytes full of essay characters inside the file memory and 4 bytes used inside the edit memory for the J O H N characters. However. Because you might want to copy a paragraph, an whole essay page or even the whole essay Microsoft Word 2007 has to make sure it has allocated enough edit memory for these situations. The same applies to the file memory – It might not be allocated just 1000 bytes for the essay characters, but perhaps 3000 bytes just in case you need to add more to the essay (i.e you start copying bits out of an History/Research file into the essay or you just type more characters into the essay). So the essay might need 5000 bytes in total allocated for it. Once you have finished editing the essay, which is in file memory at this point, you then tell Microsoft Word 2007 to save the file memory back onto the floppy disk as an essay file.

A collection of bytes is known as Data. Microsoft Word 2007 sees files and memory as a block of data only, which means when it opens a file and copies it into memory all it is doing is copying a block of data from one place (i.e Floppy Disk) to another (i.e Memory). So when it saves the essay file from file memory to floppy disk it just sees it as copying a block of data from one place to another. And that is how you should see files and memory – as blocks of data. Once the essay (file memory) has been saved onto the floppy disk as an essay file the file memory and edit memory are released for other programs to use.

The above is okay when everything is running smoothly, but problems arise when a program tries to allocate memory that is not available. For example. If you try to open too many programs or files at once they might crash (Freeze/Stop) Windows Vista. This would be due to the programs either not having enough memory to open themselves (i.e show their own windows) or not enough memory for their additional needs, such as editing files. For example. If there are only 10,000 bytes of memory remaining and two newly opened programs are waiting for 50,000 bytes of memory each they will be put in a waiting queue. Waiting forever. Or at least until another program closes and releases its memory, but it might only be releasing 4000 bytes of memory. In which case one of the waiting programs could use the 4000 bytes now available and then wait for the other 46,000 bytes to become available. On the other hand, the programs might get sick of waiting and decide to close. Either way it is a slow and messy process. This is why you should get to know the limits of your computer first before opening too many programs at once. Another scenario is memory corruption. Basically this is when a program misinterprets some byte values. For example. If a language program is supposed to read 74, in a settings file, as English but sees (reads) 77 instead. It would probably show text in a different language – Not much harm as you could probably change the language setting back to English once the language program had opened and fully completed. However. Imagine if a program interprets a byte value of 100 to mean you have paid/registered to use that program and a byte value of 101 to mean you are just trying out that program for 30 days. You might of paid £30 for a program that is saying you have not paid, but you are just trying it out.

Concern by jess: Would any WXGA display suit an Acer laptop, or does is especially have to be an Acer component?
I’m finding a laptop with a damaged display, and I was wondering if I necessary specific areas from Acer, or if I could just get a generic screen and use that as an alternative? Anyone have any experience of this?

Greatest reply:

Solution by David Bobb
Get the specific ACER screen. The reason is that each and every laptop is developed differently, using distinct sorts of cables, and hinges and measurements. The only way to assure that the new display will match is to get one that is certain to your laptop computer model.

Know better? Depart your personal answer in the comments!

Thank you for your help.

Best answer:

Answer by C
something such as an Panosonic Toughbook this has the serial ports ect and is a fully rugged laptop. they are hard to get hold of so i would suggest eBay. you could also try ITronics

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