byte question

[bagawitz]

Hello. I was wondering if anyone could explain to me how bits are physically grouped together to form a byte of addressable memory? Thanks.

 

[bagawitz]

Just realized I may not have asked the question properly. What I am curious about is how a memory location can be read as a group of bits (byte, word, etc.) rather than only as a bit. Thanks.

 

[DeathMagus]

Just realized I may not have asked the question properly. What I am curious about is how a memory location can be read as a group of bits (byte, word, etc.) rather than only as a bit. Thanks.

Shot in the dark, here - I would think that a memory location is only assigned every 8 bits for convenience. I assume that each memory location would have at least a header(a footer might not be necessary, if each memory location has the same number of bits). If you're taking up space with headers, it wouldn't be prudent to put a header with every bit, because your overhead would skyrocket. You'd also have more seek requests, since each bit would have to be called individually. By calling whole bytes at a time, only 1 request is sent for a block of 8 bits, saving time. You might acquire some bits you don't need, but it's still more efficient in the long run.

But that's just my wild guess. I would love to be corrected if that's not right.

 

[Soul Searcher]

I can't say with certianty either but I agree that data is likely read in complete bytes. I do not think that there is header and footer information for the bytes in the memory as this could reduce the usable memory to 1/3 the total. e.g. 1 byte for header 1 byte for data 1 byte for footer.

Memory is referenced by address. When a program assigns a variable it allocates a portion of memory and then uses the address of that memory to store and retrieve the data. The pointer is also stored in memory so the program knows where to begin reading when that variable is needed.

I normally don't work at the lowest levels so my knowledge of the low level functions is spotty. In higher level languages there is not a big need to understand the very low level stuff though I am sure it would have its uses. In higher level languages the programmer needs to know the data types. Visual Basic for example uses 2 bytes for an integer so any time you define a variable as an integer it allocates 2 bytes of data memory to hold the variable then when you read the variable it reads two bytes of memory. Some variables such as strings can have variable lengths in which case there is a delimiter set up to tell the system how many bytes to read.

In C strings have a null terminator and you can reference memory directly by a memory location. It is very powerful but the programmer must know what he/she is doing or will get strange unpredictable results. In VB if you have defined an integer [2 bytes] and try to place a number that requires more than 2 bytes it will generate an overflow error. C will not but rather will write the data to memory at the given location. The result is that it overflows the defined space and flows into the next memory location which may or may not already be assigned to another variable and this is the reason for the strange and unpredictable results than can sometimes happen.

 

[pgp_protector]

Bit = 1 Bit of Data
Byte = 8 Bits Of Data.

How the Memory Actually works
http://en.wikipedia.org/wiki/Dynamic_random_access_memory

 

[pgp_protector]

SDRAM -> http://en.wikipedia.org/wiki/DDR_SDRAM
Static RAM -> http://en.wikipedia.org/wiki/Static_random_access_memory
ROM (Read Only Memory) -> http://en.wikipedia.org/wiki/Read-only_memory
Then you also have PROM, EPROM, EEPROM