2. Registers

Low level languages make direct use of the hardware within the CPU. This means the programmer needs to know a lot about the internal structure of the CPU in order to write low level code.

In particular, they to know about the registers within the CPU

A register is a discrete memory location within the CPU designed to hold temporary data and instructions

A modern CPU will has many internal registers. They include a number of general purpose registers that the programmer can use to hold intermediate results whilst working through a calculation or algorithm.

Then there are special-purpose registers designed to carry out a specific role. Each of these registers are given a name so that the programmer can write their software code to access them. Different manufacturers of CPU chips call them by different names (which makes life interesting for a professional programmer!)

Registers change value under the command of the currently running program and they do so with every tick of the system clock as shown below.