RUNNING AND DEBUGGING TIPS

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1. Do not attempt to use a subscript that is out of range. Suppose we have

int List [6];

An inadvertent reference such as

for (J = 1; J <= 6 ; J++) List[J]= J;

will destroy the contents of memory not associated with array List (List[6]); this memory may contain another variable, part of the compiler, part of the operating system, or be unused at the moment. The results are unpredictable and are often destructive.

# define Length 100

int

A[Length];

b. Attempting to compare A[J – 1] to A[J]. This presents the same problem at the beginning of an Array. Remember; J – 1 cannot have a value less than 0.

the search

Index = 1; Length = 4; while (Num != A[Index]) && (Index < Length) ) Index = Index + 1;

yields values

Since this loop can be terminated by either (a) finding the sought number (Num) or by (b) exhausting the search of the array, it is imperative that you remember to check to see that ( A[Index]==Num ) before making logical decisions based on a successful search.

SUMMARY

Key Terms / Words

array

character array (string)

component (element, cell) of an Array

End-of-String Marker

index (subscript)

pointer arithmetic

pointer decrementation

pointer incrementation

selection sort

sequential search

# define MAX 10 int X[MAX+1];

Arrays can be visualized as lists; thus, the previous Array could be envisioned as either of the following:

Each component of an Array is a variable of the declared type (int, float, double, char, long int, long double, boolean, etc.).
Loops can be used to fill an array with random information.

for (Index = 1; Index <= MAX_ROLLS; Index ++) { Die = (int) (rand()/32768.0 * 6 + 1); DiceDistribution[Die] ++; }

int No[100], Ptr = &No[0], Index; for (Index = 0; Index < 100; Index ++, Ptr++) *Ptr = Index;

do { printf ("Enter Score A[%d] <-1 to exit> : ",ActNo+1); scanf ("%d ",&Temp); if (Temp != -1 ) { ActNo++; List[ActNo] = Temp; } } while (Temp != -1);

Loops can be used to print data from Arrays.

for (Index = 1; Index <= MAX_ROLLS; Index ++) printf ("DiceDistribution[%d] = %8.2f\n", DiceDistribution[Index];

Loops can be used perform calculations with Arrays, such as average, sum, etc.

for (Sum = 0, Index = 1; Index <= ActNo; Index ++) Sum += List[Index]; Average = Sum/ActNo;

Manipulating components of an Array is generally accomplished by using the index as a loop variable; for example, assuming the previous Score, to find the smallest value in the Array we can use

Smallest = List[1]; for (Index = 2; Index <= ActNo; Index ++) if (List[Index} < Smallest) Smallest = List[Index];

A selection sort is one method of sorting elements in an Array from high to low or low to high; for example, if A is an Array of length N, a low–to–high sort is

for (J = 1; J <= N–1; J++ ) { Index = J; for (K = J + 1; K <= N; K++ ) if (A[K] < A[Index]) Index = K; Temp = A[Index]; A[Index] = A[J]; A[J] = Temp; }

Arrays may be passed to subprograms as an array

main() { int X[10]; InitializeArrayToZero (X, 10); } void InitializeArrayToZero (int List[], int Max) { int Subscript; for (Subscript = 0; Subscript < Max; Subscript++) List[Subscript]=0; }

main() { int X[10]; InitializeArrayToZero (&X, 10); } void InitializeArrayToZero (int *Ptr, int Max) { int Subscript; for (Subscript = 0; Subscript < Max; Subscript++, Ptr++) (*Ptr) = 0; }

Sorting Arrays is conveniently done using functions, Good program design insists such functions should be written generic enough to support passing a variety of arrays of that data type.

Index = 1; while ( (SoughtNum != List[Index]) && (Index < ActNo) ) Index++; if (SoughtNum == List[Index]) printf ("%d is in position %d of List\n",SoughtNum,Index); else printf ("%d is not in List\n",SoughtNum);

Index = 1; while ( (SoughtNum > List[Index]) && (Index < ActNo) ) Index++; if (SoughtNum == List[Index]) printf ("%d is in position %d of List\n",SoughtNum,Index); else printf ("%d is not in List\n",SoughtNum);

A binary search of a list consists of deciding which half of the list contains the value in question and then which half of that half, and so on; code for this search is

First = 1; Last = ActNo; Found = False; while ((!Found) && (First <= Last)) { Mid = (First + Last) / 2; if (SoughtNum == List[Mid]) Found = True; else if (SoughtNum > List[Mid]) First = Mid + 1; else Last = Mid – 1; }

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For each of the programs below

(A) construct the hierarchy structure chart

(B) write the pseudocode for all modules

(C) create a working copy [attractively include the computer scientist name(s) on the output screen for each program]

(D) test the program

(E) document the program and each module in accordance with your instructor's requirements.

9. The Game of Nim is played with three piles of stones. There are three stones in the first pile, five stones in the second, and eight stones in the third. Two players alternate taking as many stones as they like from any one pile. Play continues until someone is forced to take the last stone. The person taking the last stone loses. Write a program which permits two people to play the game of Nim using an Array to keep track of the number of stones in each pile.

Sales Commission $0–1000 3% 1001–5000 4% 5001–10000 5% over 10000 6%

In addition, any salesperson who sells above the average of all salespeople receive a $50 bonus, and the top salesperson receives an addition $75 bonus.

Given the social security numbers and amounts sold by each of 20 salespeople, write a program that prints a table showing the salesperson's social security number, the amount sold, the commission rate, and the total amount earned. The average sales should also be printed.
16. Write a program that will allow you to gather information performance times to sequentially search an integer array that in internal memory. Then calculate the time to binary search the same array in internal memory. Use a spreadsheet program to produce a graph similar to that in figure 7-3.
17. Modularize program SortFloat.c. It must include the following prototypes

void SelectionSortFloat (float Array[], int ActNo); void DisplayArrayFloat (float Array[], int ActNo, char Title[]); void FillArrayFloatKeyboard (float Array[], int ActNo, float Low, float High, float Sentinel);