1. VISUAL C++ PROGRAMMING: CONCEPTS AND PROJECTS Chapter 7A Arrays (Concepts)

2. Objectives Visual C++ Programming 2  Learn how to declare and use one-dimensional arrays  Pass array elements and entire arrays into methods  Learn how to search for values in an array using the sequential search technique  Discover how two-dimensional arrays can be used to store and process tables of data  Gain further experience with nested loops

3. Arrays Visual C++ Programming 3  Data structures organize related items in memory  Arrays are data structures that consist of a contiguous block of memory cells  An array element is a single unit of data in an array  Index values (subscripts) are used to give an identifying number to each element  Index values are automatically assigned  Index values always start with 0  The last index value is one less than the number of elements If an array has 5 elements its index values go from 0 to 4

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5. Array Declaration and Initialization Visual C++ Programming 5  Fixed-size arrays are declared in several ways  By naming the array and providing a size in square brackets Example: int num[5]; Initialization by using assignment statements: num[0] = 2;  By naming the array, leaving the size empty and providing a value list to initialize it Example: int num = { 2,7,3,8,6};  Static and dynamic allocation  The number of elements in a fixed size array cannot be changed (static allocation)  In later chapters we learn dynamic allocation to create an array at runtime

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7. Array element assignment Visual C++ Programming 7

8. Using Arrays Visual C++ Programming 8 To reference the data in a particular element use the array name and the subscript of the element Example: the second element in array num is num[1] Loops work well with arrays, especially for loops The loop control variable is used as a subscript Example: for (int i=0; i < 5; i++) sum += num[i];

9. Value list declaration Visual C++ Programming 9

10. Subscript referencing Visual C++ Programming 10

11. Summation Visual C++ Programming 11

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14. Arrays and Instance Methods Visual C++ Programming 14  Arrays may need to be passed into methods  Passing a single element into a method by value The actual argument is the array element name method_name(array_name[subscript]) Example of method call: ShowNum(num[0]);

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16. Array elements as actual arguments Visual C++ Programming 16

17. Passing a single Element into a Method by Reference Visual C++ Programming 17  The actual argument must be a single array element  Example: GetNum(num[0]);  The formal parameter must be a reference parameter  Example: private: void GetNum( int& myNum) { … }

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19. Passing an Entire Array into a Method Visual C++ Programming 19  The actual argument is the array name only – no subscripts  Example:  int num[5];  GenerateData(num);  The matching formal parameter  May have any name  Its data type must match that of the actual argument  The name is followed by an empty pair of square brackets  Example: private: void GenerateData(int numArr[]) { …}  When an entire array is passed in a copy of the values is not made – all changes to array values are made to the original (similar to pass by reference)

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27. Sequential Search Visual C++ Programming 27  A sequential search is a process of looking for a particular value (target value) in an array  The array elements are accessed in order until  the target value is found  or there are no more array elements to examine

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30. Searching with a for Loop Visual C++ Programming 30  A for loop can be used for a sequential search  The loop control variable starts at element 0  The loop condition is that the loop control variable must be less than the number of elements in the array  The update condition increments the loop control variable by 1  The loop body compares the element whose subscript is the loop control variable to the target value  If a match is found a break statement breaks out of the loop

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35. Counting Comparisons Visual C++ Programming 35  To count the comparisons made by a sequential search use value in the loop control variable after the loop is over  The loop is over because either  The target was found and a break statement broke out of the loop  The target was not found after the values in all elements had been examined  In the first case the loop control variable contains the number of comparisons made  In the second case, the number of comparisons is one less than the loop control variable because the loop control variable

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37. The Search Comparison Log Visual C++ Programming 37  Keeps track of the comparisons made  Provides the details of each comparison  Concatenates the details into a large output string  Displays the output string

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39. Parallel Arrays Visual C++ Programming 39  Two or more arrays of the same length  Corresponding elements of each array are related  One array can be searched and the location result used to access related data in other arrays

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45. Multidimensional Arrays Visual C++ Programming 45  Two or more dimensions  Two dimensional array  Rows (across)  Columns (down)  Each element has both a row and column identifier  Data is stored in contiguous fashion by row but can be envisioned as a table  Nested loops are used to traverse the array The outer loop identifies the row The inner loop identifies the column

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52. Summary Visual C++ Programming 52 Arrays are data structures that store values in contiguous space in memory Fixed array sizes cannot be changed Array elements are designated using subscript values Loop control variables (especially in for loops) can be used to access values stored in each element of an array Summation Finding the largest value Sequential search

53. Summary (continued) Visual C++ Programming 53 Array elements can be passed into methods by value or by reference Actual arguments must identify the element by its subscript Entire arrays are passed into methods as actual arguments using the array name When entire arrays are passed in a copy of the array is not made (not passed by value) An array can be searched sequentially Until the target is found or there are no more elements to examine

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