Semiconductor memory is a digital electronic data storage device, often used as computer memory, implemented with semiconductor electronic devices on an integrated circuit (IC). There are many different types of implementations using various technologies.
Most types of semiconductor memory have the property of random access, which means that it takes the same amount of time to access any memory location, so data can be efficiently accessed in any random order. This contrasts with data storage media such as hard disks and CDs which read and write data consecutively and therefore the data can only be accessed in the same sequence it was written. Semiconductor memory also has much faster access times than other types of data storage; a byte of data can be written to or read from semiconductor memory within a few nanoseconds, while access time for rotating storage such as hard disks is in the range of milliseconds. For these reasons it is used for main computer memory (primary storage), to hold data the computer is currently working on, among other uses.
Shift registers, processor registers, data buffers and other small digital registers that have no memory address decoding mechanism are not considered as memory although they also store digital data.