Data storage Flashcards
Cell
A unit of memory - 1 bit
Logic 1 logic 0
logic 1 - high voltage level
logic 0 - low voltage level
order
high order end of memory is most significant bit (MSB)
low order end of memory is least significant bit (LSB)
what identifies a group of cells in main memory
address
how are addresses in main memory named
They are numbers (hex) and assigned consecutively starting at zero
Main memory refers to
RAM (Random access memory)
CPU has fast access to and is volatile
data in RAM is ‘lost’ when machine is shut down
Accessing RAM
non-sequential access, time to access any address in RAM is constant
what does ram store
the data, instructions and results of the program currently being executed by the processor and the temporary data which is frequently used
two types of ram
static RAM -
- cells composed of flip-flops (needs continuous power)
- used for a computers cache as it is expensive and takes up a lot of space
- retains data bits as long as power is being supplied
dynamic RAM - each cell composed of a transistor and a capacitor (does not need continuous power).
- has to be refreshed every so often
- found in memory sticks
what is a kilobyte
1024 bytes (2^10 bytes)
what is a megabyte
1,048,576 bytes (2^20 bytes)
what is a gigabyte
1………. billion or so bytes (2^30 bytes)
nibble
4 bits
byte
8 bits
what is known as a volatile and temporary type of memory
RAM
why is mass storage advantageous over main memory
It is less volatile, larger storage capacity, low cost and can often be removed
flash memory
circuits that trap electrons in tiny silicon dioxide chambers
storage device that is subject to mechanical failure
hard disk drive
mass storage performance depends on
- Data transfer rate (total amount of bits that can be transferred in a unit of time)
- Access time (total time between the request for data transfer and its arrival)
- Reliability - measure by mean time to failure
