of coursemost programs are more complex than index cards imagine the database the department of motor vehicles (or whatever it' called in your stateuses to keep track of driverslicensesor an airline reservations system that stores passenger and flight information such systems may include many data structures designing such complex systems requires the application of software engineering techniqueswhich we'll mention toward the end of this programmer' tools not all data storage structures are used to store real-world data typicallyreal-world data is accessed more or less directly by program' user some data storage structureshoweverare not meant to be accessed by the userbut by the program itself programmer uses such structures as tools to facilitate some other operation stacksqueuesand priority queues are often used in this way we'll see examples as we go along real-world modeling some data structures directly model real-world situations the most important data structure of this type is the graph you can use graphs to represent airline routes between cities or connections in an electric circuit or tasks in project we'll cover graphs in "graphs,and "weighted graphs other data structuressuch as stacks and queuesmay also be used in simulations queuefor examplecan model customers waiting in line at bank or cars waiting at toll booth overview of data structures another way to look at data structures is to focus on their strengths and weaknesses in this section we'll provide an overviewin the form of tableof the major data storage structures we'll be discussing in this book this is bird' -eye view of landscape that we'll be covering later at ground levelso don' be alarmed if the terms used are not familiar table shows the advantages and disadvantages of the various data structures described in this book table characteristics of data structures data structure advantages disadvantages array quick insertionvery fast access if index known quicker search than unsorted array slow searchslow deletionfixed size slow insertion and deletionfixed size ordered array