When discussing branches we learnt that r15 was also called pc but we never called it r15 anymore. Well, let’s rename from now r14 as lr and r13 as sp. lr stands for link register and it is the address of the instruction following the instruction that called us (we will see later what is this). sp stands for stack pointer. The stack is an area of memory owned only by the current function, the sp register stores the top address of that stack. For now, let’s put the stack aside. We will get it back in the next chapter.