Thread: Arrays and Functions

I wrote a program to scan a Student's ID # from a file into one array, and scan their Mark from the same file into another parallel array. My code below works fine, but once I had written it all, I realised that I needed to make a function (called "getData" or something) to input the data from the file into the arrays and print the data. I did this all in main instead.

I'm just having trouble trying to figure out how to put this step into a function. Below is my working code.

Code:

/*This program will input data into two parallel arrays from scores.txt.
 *It will them print out the student's score according to their ID number.
 *
 *Input:
 *Student Number
 *
 *Outputs:
 *Student Number
 *Mark of Student
 */
 
#include <stdio.h>
#define MAXIMUM 100
#define SENTINEL -99

/*Function Prototypes*/
int searchArray (const int iArray[], int iNum, int iTarget);

int main (void)
{
	int iId[MAXIMUM], iScore[MAXIMUM];     /*Arrays*/
	int iNum, iTarget, iStatus, iPosition; /*Array Parameters*/
	FILE *inp;
	
	inp = fopen("C:/Documents and Settings/Administrator/Desktop/scores.txt", "r");
	
	if (inp == NULL)
	{
		printf("Unable to open file!\n");
		return(-1);
	}
		
	iNum = 0;
	iStatus = fscanf(inp, "%d %d", &iId[0], &iScore[0]);
	while (iStatus != EOF)
	{
		iNum++;
		iStatus = fscanf(inp, "%d %d", &iId[iNum], &iScore[iNum]);
	}

	if (iNum > MAXIMUM)
	{
		printf("Too much input data!\n");
		return (-1);
	}


	printf("Enter a student number (-99 to quit): ");
	scanf("%d", &iTarget);
	while (iTarget != SENTINEL)
	{
		iPosition = searchArray (iId, iNum, iTarget);
		if (iPosition == -1)
		{
			printf ("Not in Array!\n");
			return(-1);
		}

		printf("Student number: %d\n", iId[iPosition]);
		printf("Mark:           %d%%\n\n", iScore[iPosition]);
		printf("Enter a student number (or -99 to quit): ");
		scanf("%d", &iTarget);
	}

	fclose(inp);



	return (0);
}




/*****FUNCTIONS*****/




int searchArray (const int iId[], int iNum, int iTarget)
{
	int iFound, iPosition;
	
	/*Assume target has not been found*/
	iFound = 0;
	/*Loop until either target is found or we are at end of data*/
	iPosition = 0;
	while (iFound == 0 && iPosition < iNum)
	{
		if (iId [iPosition] == iTarget)
		{
			iFound = 1;
		}
		else
		{
			iPosition++;
		}
	}
	if (iFound == 0)
	{
		return (-1);
	}
	else
	{
		return (iPosition);
	}

}

Yes, but how do I define the function in "main"?

I guess I was just wondering how to "call" the function in main.

Code:

int main(void)
{
     getData(iId,iScore);
     etc...
}

Is this right?
Why no square brackets after the iId and iScore arrays? Why won't getData(iId[], iScore[]); work?

I have made the changes you suggested, and my program will now succesfully compile and build, but it will not run.
Here is the new code:

Code:

/*This program will input data into two parallel arrays from scores.txt.
 *It will them print out the student's score according to their ID number.
 *
 *Input:
 *Student Number
 *
 *Outputs:
 *Student Number
 *Mark of Student
 */
 
#include <stdio.h>
#define MAXIMUM 100
#define SENTINEL -99

/*Function Prototypes*/
int getData(int iId[], int Score[]);
int searchArray (const int iArray[], int iNum, int iTarget);

int main (void)
{
	int iId[MAXIMUM], iScore[MAXIMUM];     /*Arrays*/
	int iNum, iTarget, iPosition; /*Array Parameters*/
	
	/*Call Function to get data*/
	getData(iId, iScore);

	if (iNum > MAXIMUM)
	{
		printf("Too much input data!\n");
		return (-1);
	}

	printf("Enter a student number (-99 to quit): ");
	scanf("%d", &iTarget);
	while (iTarget != SENTINEL)
	{
		iPosition = searchArray (iId, iNum, iTarget);
		if (iPosition == -1)
		{
			printf ("Not in Array!\n");
			return(-1);
		}

		printf("Student number: %d\n", iId[iPosition]);
		printf("Mark:           %d%%\n\n", iScore[iPosition]);
		printf("Enter a student number (or -99 to quit): ");
		scanf("%d", &iTarget);
	}



	return (0);
}




/*****FUNCTIONS*****/




/*Function to input the data from the file into the arrays and print the data*/
int getData(int iId[], int iScore[])
{
    int iStatus, iNum;
	FILE *inp;
	
	inp = fopen("C:/Documents and Settings/Administrator/Desktop/scores.txt", "r");
	
	if (inp == NULL)
	{
		printf("Unable to open file!\n");
		return (-1);
	}
		
	iNum = 0;
	iStatus = fscanf(inp, "%d %d", &iId[0], &iScore[0]);
	while (iStatus != EOF)
	{
		iNum++;
		iStatus = fscanf(inp, "%d %d", &iId[iNum], &iScore[iNum]);
	}
	
        fclose(inp); /*close the file*/
        return (iNum); /*return number of ints read*/
}





/*Function to search array for student #*/
int searchArray (const int iId[], int iNum, int iTarget)
{
	int iFound, iPosition;
	
	/*Assume target has not been found*/
	iFound = 0;
	/*Loop until either target is found or we are at end of data*/
	iPosition = 0;
	while (iFound == 0 && iPosition < iNum)
	{
		if (iId [iPosition] == iTarget)
		{
			iFound = 1;
		}
		else
		{
			iPosition++;
		}
	}
	if (iFound == 0)
	{
		return (-1);
	}
	else
	{
		return (iPosition);
	}

}

It won't do ***anything*** at all....It starts up, but I receive a Windows error message and the command promp shuts down.

probably because the value of iNum in main() was never set

Code:

	iNum = getData(iId, iScore);

I had fixed that, but even then, It still refuses to work.

your program works ok for me. Check the data file. It should look something on the order of this, but I just put several jumk values in it. If the file contains more than MAXIMUM number of rows then your program will crash because it does not make any sanity checks for array overflows.

Code:

10 15
20 25
21 22
1 2
3 4
5 6

Code:

	while (iStatus == 2 && iNum < MAXIMUM)

You had said that this loop of mine was not right:

Code:

	iStatus = fscanf(inp, "%d %d", &iId[0], &iScore[0]);
	while (iStatus != EOF)
	{
		iNum++;
		iStatus = fscanf(inp, "%d %d", &iId[iNum], &iScore[iNum]);
	}

But it worked perfectly when I wrote the whole program in main. Why won't it work for me now?