Array1.c. all arrays start at 0 sometimes known as a list

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1 Learning Outcomes 1) EXPLAIN AND APPLY THE CONCEPT OF A PROCEDURAL PROGRAMMING PARADIGM AND APPLY THE ASSOCIATED DESIGN PRINCIPLES TO A RANGE OF PROBLEM SOLUTIONS 2) BE ABLE TO DESIGN, IMPLEMENT, AND DOCUMENT (APPROPRIATELY) EFFICIENT ALGORITHMS 3) EXPLAIN THE STRUCTURE, CORRECT USE OF AND IMPLEMENTATION OF APPROPRIATE ADVANCED DATA STRUCTURES AND ALGORITHMS FOR A RANGE OF SCENARIOS. Knowledge & Understanding Problem Solving Application Communication Knowledge & Understanding 1) An array is also sometimes known as a? 2) Can you change the size of an array once it has been declared? 3) Can elements of an array be of different types? 4) What is the index of the first item in the array? 5) What do we mean by explicit initialisation? all arrays start at 0 sometimes known as a list Remember arrays are: a) of a FIXED SIZE b) elements are of the SAME TYPE c) referred to collectively by the same name d) stored consecutively in memory e) a constant "pointer" to the memory location that represents the first item in the array (index 0) Array1.c Create an array of 3 elements then display the values in each of these elements. #define SIZE 3 int index; 5 You declare a variable by putting your brackets after the array name with the number of elements required in brackets 4 int marks[size]; marks[0] = 59; marks[1] = 70; marks[2] = 41; Once an array has been created we can initialise/access individual elements in the array via their subscripts/index [] /*Display the contents of the marks array*/ printf("marks[%d] is %d\n", index, marks[index]); 1

2 Compare with VBA Const UPPER_INDEX As Integer = 3 Dim loop As Integer Dim marks(upper_index) As Integer For loop=0 To UPPER_INDEX msgbox marks & loop & is & marks[loop] Next 2

3 1) What do we mean by implicit initialisation? Array2.c This example shows days per month - idea from C Primer Plus Create an array holding the value of each day of the month when it is not a leap year. #define SIZE 12 Array declared and values assigned at the same time. Note the use of and } to surround the values. int days[] = 31,28,31,30,31,30,31,31,30,31,30,31}; int index; 1 printf("month %d has %d days.\n", index+1, days[index]); Contents of the days array

4 Array3.c 1) What is ONE WAY of creating strings in c? 2) Do we need to use the reference operator (&) when entering data into a string array? 3) What conversion character do we use for a string? Inputting string data into an array Ask the user to enter 5 names and store these in an array. Display the names. #define SIZE_OF_STRING 21 char name[size_of_string]; printf("enter a name:"); scanf("%s",name); printf("\nyou entered %s\n",name); getchar();//pause scanf("%s", name); Get user input using appropriate conversion specification character. Notice that the string (first) DOES NOT have a & (address operator) before it as it is a pointer. The String assigned to name will be the text up to a space or a new line even if it is more than 20 characters! 4

5 Array4.c 1) Why do we need two sets of [brackets] when defining a string array? Inputting string data into an array Ask the user to enter 5 names and store these in an array. Display the names. #define MAX 5 #define SIZE_OF_STRING 21 char names[max][size_of_string]; int index; for (index=0; index<max; index++) printf("enter a name:"); scanf("%s",names[index]); } puts("\nnames entered were:"); for (index=0; index<max; index++) printf("%s\n",names[index]); } } getchar();//pause 5

6 Array5.c 2) Do we need to use the reference operator (&) when entering data into an array? Inputting data into an array Ask the user to enter 5 integer values and store these in an array. Display the values both in the order they were entered and then again in reverse order. #define SIZE 5 Constant that refers to the number of items for the array int index;/*create loop variable*/ int test[size]; /*Input the values into the array*/ puts("enter a value"); scanf("%d", &test[index]); puts("\n\nnew values...\n"); Show the array s values printf("%d\n", test[index]); puts("\n\nvalues in reverse order...\n"); Show the array s values in reverse order for (index=size-1; index>=0; index--) printf("%d\n", test[index]); puts("\n"); 6

7 Uni1.c Enhanced University example Read in 5 values, find their average and display all values less than the average. #define SIZE 5 int index, sum=0; int a[size]; float average; /*Input the values into the array*/ puts("input the array values"); scanf("%d",&a[index]); sum+=a[index]; /*Find the average*/ average = (float) sum / SIZE; printf("the average is %.1f\n", average); /*Output the values less than the average*/ for (index=0; index<size; loop++) if(a[index]<average) printf("%d is less than average\n", a[index]); }/*end if*/ puts("\n"); #define SIZE sizeof(marks)/sizeof(int) To work out the number of entries in an array we can use the sizeof operator which returns the number of bytes in use. As this is dependent upon the type of variable used for the array you need to divide the size of the array by the size of the type - this will then give the number of elements in the array. 7