In the following paragraph its talking about memory and it throws M into the L X W of memory notation and i'm confused on how 4M = 2^22. Thanks in advance
Memory is built from random access memory (RAM) chips. (We cover memory in detail in Chapter 6.) Memory is often referred to using the notation length X width (L X W). For example, 4M X 8 means the memory is 4M long (it has 4M = 2^2 X 2^20 = 2^22 items) and each item is 8 bits wide (which means that each item is a byte). To address this memory (assuming byte addressing), we need to be able to uniquely identify 2 ^ 22 different items.