What?
Little dedicated storages for small bits of data (EG For program variables and control state). MIPS (Architecture) processes operate on registers only.
Registers are generally sized to contain a machine’s word (32/64 bit - 32bit for MIPS (Architecture)). What’s this? The standard size of data that the ISA (Instruction Set Architecture) is designed to handle efficiently.
Layout:
Within a register, data is stored. Each entry of data is typically 32 bits. Thus the byte address is typically also given. The fact each entry is stored in bytes (multiples of 8) is called and Alignment Restriction.
What happens when variables > registers?
If a program has more variables than chip has registers, the values in the registers get spilled into (Computer) Memory Conceptually. This is less than ideal.
Actually what is it in Digital Circuits:
It’s a bunch of d flip-flops strung together using a common clock.