low-level arrays to accurately describe the way in which python represents the sequence typeswe must first discuss aspects of the low-level computer architecture the primary memory of computer is composed of bits of informationand those bits are typically grouped into larger units that depend upon the precise system architecture such typical unit is bytewhich is equivalent to bits computer system will have huge number of bytes of memoryand to keep track of what information is stored in what bytethe computer uses an abstraction known as memory address in effecteach byte of memory is associated with unique number that serves as its address (more formallythe binary representation of the number serves as the addressin this waythe computer system can refer to the data in "byte # versus the data in "byte # ,for example memory addresses are typically coordinated with the physical layout of the memory systemand so we often portray the numbers in sequential fashion figure provides such diagramwith the designated memory address for each byte figure representation of portion of computer' memorywith individual bytes labeled with consecutive memory addresses despite the sequential nature of the numbering systemcomputer hardware is designedin theoryso that any byte of the main memory can be efficiently accessed based upon its memory address in this sensewe say that computer' main memory performs as random access memory (ramthat isit is just as easy to retrieve byte # as it is to retrieve byte # (in practicethere are complicating factors including the use of caches and external memorywe address some of those issues in using the notation for asymptotic analysiswe say that any individual byte of memory can be stored or retrieved in ( time in generala programming language keeps track of the association between an identifier and the memory address in which the associated value is stored for exampleidentifier might be associated with one value stored in memorywhile is associated with another value stored in memory common programming task is to keep track of sequence of related objects for examplewe may want video game to keep track of the top ten scores for that game rather than use ten different variables for this taskwe would prefer to use single name for the group and use index numbers to refer to the high scores in that group