move exercises and lectures into subfolders

Exercises/C14/Makefile

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+include ../Makefile

Exercises/C14/ex1.c

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+#include <stdio.h>
+#include <math.h>
+
+void cartesian_to_polar(float x, float y, float *r, float *theta) {
+	*r = sqrtf(x*x + y*y);
+	*theta = y/x;
+}
+
+int main() {
+	int rc;
+	float x, y, r, theta;
+
+	printf("x: ");
+	rc = scanf("%f", &x);
+	// check that scanf was successful by checking if it returned 1 (1 successfully scanned item)
+	if (rc != 1) {
+		printf("Please enter a real number\n");
+		return 1;
+	}
+
+	printf("y: ");
+	rc = scanf("%f", &y);
+	if (rc != 1) {
+		printf("Please enter a real number\n");
+		return 1;
+	}
+
+	cartesian_to_polar(x, y, &r, &theta);
+	printf("r=%f theta=%f\n", r, theta);
+
+	return 0;
+}

Exercises/C14/ex2.c

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+#include <stdio.h>
+#include <math.h>
+
+
+float degrees_to_radians(float degrees) {
+	return M_PI * degrees / 180.0;
+}
+
+void process(float degrees, float* radians, float* sin_val, float* cos_val, float* tan_val) {
+	*radians = degrees_to_radians(degrees);
+	*sin_val = sin(*radians);
+	*cos_val = cos(*radians);
+	*tan_val = tan(*radians);
+}
+
+
+int main() {
+	float degrees, radians, sin_val, cos_val, tan_val;
+
+	printf("Degrees: ");
+	scanf("%f", &degrees);
+
+	process(degrees, &radians, &sin_val, &cos_val, &tan_val);
+
+	printf("Radians: %f\n", radians);
+	printf("Sine: %f\n", sin_val);
+	printf("Cosine: %f\n", cos_val);
+	printf("Tangent: %f\n", tan_val);
+}

Exercises/C14/ex3.c

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+#include <stdio.h>
+#include <math.h>
+
+
+float degrees_to_radians(float degrees) {
+	return M_PI * degrees / 180.0;
+}
+
+void process(float degrees, float* radians, float* sin_val, float* cos_val, float* tan_val) {
+	*radians = degrees_to_radians(degrees);
+	*sin_val = sin(*radians);
+	*cos_val = cos(*radians);
+	*tan_val = tan(*radians);
+}
+
+
+int main() {
+	int degrees_start, degrees_end;
+	float radians, sin_val, cos_val, tan_val;
+
+	printf("Start: ");
+	scanf("%d", &degrees_start);
+	printf("End: ");
+	scanf("%d", &degrees_end);
+	printf("Degs\tRad\tsin\tcos\ttan\n");
+
+	for (int i = degrees_start; i <= degrees_end; i++) {
+		process((float)i, &radians, &sin_val, &cos_val, &tan_val);
+		printf("%d\t%0.3f\t%0.3f\t%0.3f\t%0.3f\n", i, radians, sin_val, cos_val, tan_val);
+	}
+
+
+}

Exercises/C14/quadratic_solver.c

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+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+int SolveQuadraticEquation(float a, float b, float c, float *x1, float *x2)
+{
+    float d;    // For storing b^2 - 4*a*c
+
+    if ( a == 0)    // Not a quadratie
+    {
+        return -1;
+    }
+
+    // calculate and store b*b-4*a*c for testing ans use later (if OK)
+    d = b*b - 4*a*c;
+
+    if ( d < 0 )
+    {
+        return -1;  // Complex
+    }
+
+    // If we have got to here, we can calculate x1 and x2
+    *x1 = ( -b + sqrt (d)) / (2 * a);  // Note the use of the * before x1 & x2
+    *x2 = ( -b - sqrt (d)) / (2 * a);  // to write to the relevant memory locations 
+
+    // As we got here OK, return 0 to indicate all is OK
+    return 0;
+}
+
+int main (void ) 
+{
+    float A,B,C,x1,x2;
+    int retval;
+
+    printf ("Please enter coefficients A,B and C separated by a space\n");
+    scanf ("%f %f %f", &A, &B, &C);
+
+    // Make use of the function
+    retval = SolveQuadraticEquation(A, B, C, &x1, &x2);
+
+    // Use the retval to determine if we can display the answers or an derror message
+    if ( retval == -1 )
+    {
+        printf ("Not a quadratic\n");
+    }
+    else if (retval == -1)
+    {
+        printf ("The solution is complex - I cannot solve these\n");
+    }
+    else
+    {
+        printf("\nThe solutions are x1=%f, x2=%f", x1, x2);
+    }
+    return 0;   // exit
+}

Exercises/C14/quadratic_solver_function.c

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+int SolveQuadraticEquation(float a, float b, float c, float *x1, float *x2)
+{
+    float d;    // For storing b^2 - 4*a*c
+
+    if ( a == 0)    // Not a quadratie
+    {
+        return -1;
+    }
+
+    // calculate and store b*b-4*a*c for testing ans use later (if OK)
+    d = b*b - 4*a*c;
+
+    if ( d < 0 )
+    {
+        return -1;  // Complex
+    }
+
+    // If we have got to here, we can calculate x1 and x2
+    *x1 = ( -b + sqrt (d)) / (2 * a);  // Note the use of the * before x1 & x2
+    *x2 = ( -b - sqrt (d)) / (2 * a);  // to write to the relevant memory locations
+
+    // As we got here OK, return 0 to indicate all is OK
+    return 0;
+}