Arrays

1. Arrays • The simple built-in data types of the C language such as int, float, -are not sufficient to represent complex data such as lists, tables, vectors, and matrices. • Sortingand searchingrequire an entire list of data to be stored in memory. • The most convenient way to accomplish this is to store the data in a one-dimensional array.

2. One-Dimensional Arrays • An arrayis a named sequence of memory locations that is used to store different values of the same data type. • Each of the named memory locations is called an element of the array. The elements of an array are identified by a subscript or an index (0,1,2,3,4). • Above, x is the name of the array, containing the elements x[0], x[1], x[2], x[3], and x[4].

3. Array Declaration and Initialization In C, there are two ways to represent a subscripted variable such as: ai i = 0 to 9 The first way it can be represented is as regular variables, as we have been doing so far: a0, a1, a2, a3, a4, a5, a6, a7, a8, a9 The above are ten different, explicitly named variables. However, if you have a large number of named variables, it is not practical to name them as shown above. Instead, we use subscripts (or array) as shown below: a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7], a[8], a[9] The above is a declaration of an array a which holds 10 different items such as int, or float. The declaration, initialization of arrays is as follows:  //declare the array int i;//declare an integer named i int a[5]; //declare array a: a[0], a[1], a[2], a[3], a[4]  for(i = 0; i < 5; i++)//loop to go through array { a[i] = 2; // initialize array aequal to 2 }

4. Arrays Declaration and Initialization  One-dimensional arrays may be declared individually as follows: int count[10]; float pressure[20]; float temperature[40]; float velocity[40]; Or all of the float data types can be declared in one declaration statement as follows: float pressure[20], temperature[40], velocity[40]; One-dimensional arrays may be initialized in a declaration statement as follows: inta[5] = {5, 9, 8, 4, 7}; //where a[0] is 5, a[1] is 9, a[2] is 8, a[3] is 4, and a[4] is 7 The following example shows the initialization of fewer values than the size of the array: int a[5] = {5, 9, 8, 4}; //where a[0] is 5, a[1] is 9, a[2] is 8, a[3] is 4, and a[4] is 0 Notice that the unspecified element a[4] is 0. If a value is not specified, then a zero is assigned.

5. Arrays Declaration/Initialization One-dimensional arrays may be initialized using assignment statements as follows: int a[5]; a[0] = 5; a[1] = 9; a[2] = 8; a[3] = 4; a[4] = 7; Initialization is usually quickly done with a for loop as follows:  int i, count [5]; float velocity[10]; for(i = 0; i < 5; i++){ count[i] = 2; } for(i = 0; i < 10; i++){ velocity[i]= 500.75; }

6. Array Input/Output

7. Sorting algorithms: • Bubble sort is a simple sorting algorithm that works by repeatedly stepping through the list to be sorted • It compares each pair of adjacent items and swaps them, if they are in the wrong order. • Every pass, the largest value “bubbles up” to the top. for(int x=0; x<n; x++) { for(int y=0; y<n-1; y++) { if( array[y] > array[y+1]) { int temp = array[y+1]; array[y+1] = array[y]; array[y] = temp; } } }

8. H.W. Arrays • Compile and run the program on slide 6 - Save it as sampleArrays.c • Write a program to: • Ask the user for 7 temperature and 7 pressure values for a scientific experiment. • Store the values in two one-dimensional arrays. • Identify the highest temperature and pressure. • Show the highest temperature and pressure to the user. • Save your program as tempPressArrays.c