Презентация «Programming Logic and Design Seventh Edition»
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Programming Logic and Design Seventh Edition Chapter 6 Arrays
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Objectives In this chapter, you will learn about: Storing data in arrays How an array can replace nested decisions Using constants with arrays Searching an array for an exact match Using parallel …
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Objectives (continued) Searching an array for a range match Remaining within array bounds Using a for loop to process arrays
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How Arrays Occupy Computer Memory Array A series or list of variables in computer memory All variables share the same name Each variable has a different subscript Subscript (or index) Position number …
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Each item has the same name and the same data type Each item has the same name and the same data type Element: an item in the array Array elements are contiguous in memory Size of the array: the …
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How Arrays Occupy Computer Memory (continued)
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How an Array Can Replace Nested Decisions Example: Human Resources Department Dependents report List employees who have claimed zero through five dependents Assume no employee has more than five …
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How an Array Can Replace Nested Decisions (continued) The array reduces the number of statements needed Six dependent count accumulators are redefined as a single array Variable as a subscript to the …
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How an Array Can Replace Nested Decisions (continued)
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How an Array Can Replace Nested Decisions (continued) Figure 6-7 Flowchart and pseudocode for Dependents report program (continued)
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Using Constants with Arrays Use constants in several ways To hold the size of an array As the array element values As an array subscript
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Using a Constant as the Size of an Array Avoid “magic numbers” (unnamed constants) Declare a named numeric constant to be used every time the array is accessed Make sure any subscript remains less …
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Using Constants as Array Element Values Sometimes the values stored in arrays should be constants Example string MONTH[12] = "January", "February", "March", …
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Using a Constant as an Array Subscript Use a numeric constant as a subscript to an array Example Declare a named constant as: num INDIANA = 5 Display value with: output salesArray[INDIANA]
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Searching an Array for an Exact Match Sometimes you must search through an entire array to find a value Example: mail-order business Item numbers are three-digit, non-consecutive numbers Customer …
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Searching an Array for an Exact Match (continued) Flag: a variable that indicates whether an event occurred Technique for searching an array Set a subscript variable to 0 to start at the first …
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Using Parallel Arrays Example: mail-order business Two arrays, each with six elements Valid item numbers Valid item prices Each price in the valid item price array is in the same position as the …
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Using Parallel Arrays (continued)
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Using Parallel Arrays (continued) Use parallel arrays Two or more arrays contain related data A subscript relates the arrays Elements at the same position in each array are logically related Indirect …
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Improving Search Efficiency The program should stop searching the array when a match is found Set a variable to a specific value instead of letting normal processing set it Improves efficiency The …
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Improving Search Efficiency (continued)
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Searching an Array for a Range Match Programmers may want to work with ranges of values in arrays, 1 through 5 or 20 through 30 Example: mail-order business Read the customer order data; determine …
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Searching an Array for a Range Match (continued)
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Searching an Array for a Range Match (continued) Drawbacks of first approach Requires a very large array; uses a lot of memory Stores the same value repeatedly How do you know when you have enough …
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Searching an Array for a Range Match (continued)
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Remaining within Array Bounds Every array has a finite size Number of elements in the array Number of bytes in the array Arrays are composed of elements of the same data type Elements of the same …
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Remaining within Array Bounds (continued)
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Remaining within Array Bounds (continued) Program logic assumes every number entered by the user is valid When an invalid subscript is used: Some languages stop execution and issue an error Other …
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Using a for Loop to Process Arrays for loop: a single statement Initializes the loop control variable Compares it to a limit Alters it The for loop is especially convenient when working with arrays …
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Using a for Loop to Process Arrays (continued)
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Using a for Loop to Process Arrays (continued)
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Summary Array: a named series or list of values in memory Same data type Different subscript Use a variable as a subscript to the array to replace multiple nested decisions Constants can be used to …
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Summary (continued) Parallel arrays: each element in one array is associated with the element in a second array Elements have the same relative position For range comparisons, store either the low- …
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Summary (continued) Access data in an array Use a subscript containing a value that accesses memory occupied by the array A subscript is out of bounds if it is not within the defined range of …
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