Initial commit of lecture code

LC17/DynamicFunction.c

@@ -0,0 +1,79 @@
+/* An example of
+
+	Creating dynamically an array
+	Populating the array
+	Displaying the contents
+	Freeing up the memory
+
+	Version 4 : Check memory has been assigned
+		    Read and Write values using pointers
+		    Pass array data to a function
+
+
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+
+
+int Sum ( int *Data, int n )	/* Define our function 			*/
+{
+    int Sum = 0,i;		/* Define working variables 		*/
+
+    for ( i = 0 ; i < n ; i++ )
+    {
+        printf("Item %d=%d\n", i, Data[i]);
+        Sum += Data[i];		/* This means   Sum = Sum + Data[i] 	*/
+    }
+
+
+    return Sum;			/* Return the value			*/
+
+}
+int main(void)
+{
+    int *ipArray = NULL;		/* Create the pointer and set   */
+    /* to null to start with 	*/
+
+    int *ipStartValue = NULL;	/* A place to store ipArray's   */
+    /* initial value ,ie ipArray[0] */
+    int iSize = 0;		/* Define our 'size' variable 	*/
+
+    int i;			/* A Loop variables 	        */
+
+    /* Prompt for array size */
+
+    printf("\nHow big is the array to be ? ");
+    scanf("%d",&iSize);
+
+    /* Allocate the memory */
+    ipArray = (int *)calloc(iSize, sizeof(int));
+
+    if ( ipArray == NULL )
+    {
+        printf("\nUnable to allocate the memory requested");
+        printf("\n  ** Program terminating ** \n");
+        exit (1);
+    }
+
+    /* Store the base memory address for use later */
+    ipStartValue = ipArray;
+
+    /* Populate the array (Method 2 - Use Pointers: This is much faster !) */
+    for ( i = 0 ; i < iSize ; i++ )
+        ipArray[i] = i;
+
+    /* Display the sum of the values in the array */
+
+    printf("\nThe sum of the array values is %d ",Sum(ipArray,iSize) );
+
+    /* free memory : Again, reset ipArray to its origin */
+
+    ipArray = ipStartValue;
+    free(ipArray);
+
+    /* The above two lines could be replaced with    free (ipStartValue)   */
+
+    return 0;
+}
+

LC17/Quadratic_with_Pointers.c

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+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+
+// This function will return
+//
+//  0   if the equation can be solved,
+//  -1  if it is not a quadratic
+//  -2  if it is complex
+
+int SolveQuadratic ( int a, int b, int c, float *x1, float *x2)
+{
+    int d;
+
+    // If the equations is not a quadratic return -1
+    if ( a == 0 )
+        return (-1);
+
+    // Calculate the value that will be square rooted
+    d = (b*b) - (4*a*c);
+
+    // If less than zero then it would be complex - give up!
+    if ( d < 0 )
+        return (-2);
+
+    // If we got to here we are OK to solve things
+    *x1 = (-b - sqrt(d)) / (2*a);
+    *x2 = (-b + sqrt(d)) / (2*a);
+
+    // This is are 'OK' return value
+    return 0;
+
+}
+
+int main()
+{
+    int A,B,C, r;
+    float X1, X2;
+
+    printf ("Please enter a b & c separated by a space: ");
+
+    scanf("%d %d %d",&A, &B, &C);
+
+    r = SolveQuadratic(A,B,C, &X1, &X2);
+
+    // The value returned lets us know if we have values in X1 and X2 we can use
+    switch (r)
+    {
+    case 0 :
+        printf ("The solutions are %f and %f", X1, X2 );
+        break;
+    case -1 :
+        printf ("The equation provided was not a quadratic" );
+        break;
+    case -2 :
+        printf ("The solutions had complex roots and could not be solved");
+        break;
+    }
+    return 0;
+}