move exercises, lecture examples, labs into subfolders

Exercises/C18/ex6.c

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+#include <stdio.h>
+#include <stdlib.h>
+
+
+int main() {
+	FILE *fp;                    // file pointer
+	float *data;                 // data pointer (array of floats)
+	int i, file_size, arr_size;
+	char filename[2049];
+
+	printf("Enter filename to read: ");
+	scanf("%2048s", filename);
+
+	fp = fopen(filename, "rb");
+	if (fp == NULL) {
+		printf("Failed to open file\n");
+		return 1;
+	}
+
+	// get file size (technically isn't the best way because SEEK_END is undefined behaviour:
+	//
+	// "Library implementations are allowed to not meaningfully support SEEK_END
+	// (therefore, code using it has no real standard portability)."
+	// ~ https://cplusplus.com/reference/cstdio/fseek/
+	//
+	// " Setting the file position indicator to end-of-file, as with fseek(file, 0, SEEK_END),
+	// has undefined behavior for a binary stream (because of possible trailing null characters) or
+	// for any stream with state-dependent encoding that does not assuredly end in the initial shift
+	// state. "
+	// ~ https://port70.net/~nsz/c/c11/n1570.html#note268
+	//
+	// it is also limited to 2GB files as it returns a signed integer
+	// better to use something like this probably:
+	// https://stackoverflow.com/a/238609
+	//
+	// but louise uses fseek so i will too
+	fseek(fp, 0, SEEK_END);
+	file_size = ftell(fp);
+	arr_size = file_size/sizeof(float);
+	rewind(fp);
+
+	// allocate memory and read data
+	data = malloc(file_size);
+	fread(data, sizeof(float), arr_size, fp);
+
+	for (i = 0; i < arr_size; i++) {
+		printf("%d %0.3f\n", i, data[i]);
+	}
+
+	free(data);
+}