diff --git a/Exercises/C20/ex1.c b/Exercises/C20/ex1.c
new file mode 100644
index 0000000..8c57847
--- /dev/null
+++ b/Exercises/C20/ex1.c
@@ -0,0 +1,125 @@
+// Modified from C18 Ex5
+#include <stdio.h>
+#include <math.h>
+#include <stdlib.h>
+
+#define DEBUG_MAIN
+#define DEBUG_FNS
+
+
+float degrees_to_radians(float degrees) {
+#ifdef DEBUG_FNS
+	printf("degrees_to_radians(degrees=%f): called\n", degrees);
+#endif
+	return M_PI * degrees / 180.0;
+}
+
+
+// Simple function to populate an integer array
+void PopulateTheArray ( int Size, float ArrayData[])
+{
+#ifdef DEBUG_FNS
+	printf("PopulateTheArray(Size=%d, ArrayData): called\n", Size);
+#endif
+    int i;      // Variable to use in our loop
+
+    for ( i = 0 ; i < Size ; i++)
+    {
+        ArrayData[i] = degrees_to_radians(i); // Treat it like a normal array
+    }
+}
+// Simple function do display contents an integer array
+void DisplayTheArray ( int Size, float ArrayData[])
+{
+#ifdef DEBUG_FNS
+	printf("DisplayTheArray(Size=%d, ArrayData): called\n", Size);
+#endif
+    int i;      // Variable to use in our loop
+
+    for ( i = 0 ; i < Size ; i++)
+    {
+#ifdef DEBUG_FNS
+	printf("DisplayTheArray(): i=%d\n", i);
+#endif
+        printf ("%d\t%0.3f\n", i, ArrayData[i]);
+    }
+}
+
+int SaveArrayBinary (char *filename, int Size, float ArrayData[])
+{
+#ifdef DEBUG_FNS
+	printf("DisplayTheArray(filename=%s, Size=%d, ArrayData): called\n", filename, Size);
+#endif
+	FILE *fp;   // File Pointer
+	int i;      // Variable to use in our loop
+
+	fp = fopen(filename, "wb");
+#ifdef DEBUG_FNS
+	printf("DisplayTheArray(): fp=%p\n", fp);
+#endif
+	// if file open failed, return error to caller
+	if (fp == NULL) {
+		return 1;
+	}
+
+	// write data
+	fwrite(ArrayData, sizeof(float), Size, fp);
+	// close file, returns 0 on successful closing (therefore function has executed sucessfully)
+	return fclose(fp);
+}
+// Main () - execution starts here
+int main (void)
+{
+#ifdef DEBUG_MAIN
+	printf("main(): called\n");
+#endif
+	char filename[2049];
+	int rc, iSizeForArray;
+	float *pData;              // A pointer to hold the base address of out array
+
+	// Ask for the size of the array and store result
+
+	printf("Please enter the size of the array to dynamically allocate: ");
+	scanf ("%d", &iSizeForArray);
+#ifdef DEBUG_MAIN
+	printf("main(): iSizeForArray=%d\n", iSizeForArray);
+#endif
+
+	// Use calloc with checking
+	pData = calloc( iSizeForArray, sizeof (float));
+#ifdef DEBUG_MAIN
+	printf("main(): pData=%p\n", pData);
+#endif
+
+	// Check we got the memory
+	if ( pData == NULL)
+	{
+		printf ("Sorry, I could not allocate the memory, bye!\n");
+		return -1;
+	}
+
+	// Pass the size, iSizeForArray) and the pointer created 
+	// which points to the start of the sucesfully allocated memory
+
+	PopulateTheArray(iSizeForArray, pData);
+	DisplayTheArray(iSizeForArray, pData);
+
+	// Exercise doesn't ask to use function but kind of pointless without
+	printf("Enter filename: ");
+	scanf("%2048s", filename);
+#ifdef DEBUG_MAIN
+	printf("main(): filename=%s\n", filename);
+#endif
+	rc = SaveArrayBinary(filename, iSizeForArray, pData);
+#ifdef DEBUG_MAIN
+	printf("main(): rc=%d\n", rc);
+#endif
+	if (rc != 0) {
+		printf("Error saving file\n");
+		free(pData);
+		return rc;
+	}
+
+	free(pData);    // Free up the memory before exiting
+	return (0);     // Exit indicating sucess
+}