Added usage string.

csim.c

@@ -4,7 +4,14 @@
 
 void print_usage()
 {
-	printf("Usage:\n");
+	printf("Usage: ./csim [-hv] -s <number> -E <number> -b <number> -t <file>\n"
+		   "Options:\n"
+		   "  -h  Print this help.\n"
+		   "  -v  Display trace info.\n"
+		   "  -s <number> The number of sets is the base-2 logarithm of this argument.\n"
+		   "  -E <number> Associativity (lines per set).\n"
+		   "  -b <number> Block size in bits is the base-2 logarithm of this argument.\n"
+		   "  -t <file>   Name of the file to read a valgrind trace from.");
 	exit(0);
 }