MDR(Memory Data Register) holds the _______________.
MDR(Memory Data Register) holds the Number of transistors.
The Memory Data Recgister (MDR) or Memory Buffer Recgister (MBR) is the register of a computer's control unit that contains the data to be stored in the computer storage (e.g. RAM), or the data after a fetch from the computer storage. It acts like a buffer and holds anything that is copied from the memory ready for the processor to use it.
The transistor count is the number of transistors on an integrated circuit (IC). Transistor count is the most common measure of IC complexity, although there are caveats. For instance, the majority of transistors are contained in the cache memories in modern microprocessors, which consist mostly of the same memory cell circuits replicated many times. The rate at which transistor counts have increased generally follows Moore's law, which observed that the transistor count doubles approximately every two years.
The MDR is a two-way register. When data is fetched from memory and placed into the MDR, it is written to go in one direction. When there is a write instruction, the data to be written is placed into the MDR from another CPU register, which then puts the data into memory.
The Memory Data Register is half of a minimal interface between a microprogram and computer storage, the other half is a memory address register (MAR).