8 files changed, 134 insertions, 0 deletions
diff --git a/C/HF/chap4/cryptic/Makefile b/C/HF/chap4/cryptic/Makefile
new file mode 100644
index 0000000..64312d5
--- /dev/null
+++ b/C/HF/chap4/cryptic/Makefile
@@ -0,0 +1,14 @@
+ecat: ecat.o encrypt.o
+	cc -o ecat ecat.o encrypt.o
+
+ecat.o: encrypt.h ecat.c
+	cc -c ecat.c
+
+message: message.o encrypt.o
+	cc -o message message.o encrypt.o
+
+message.o: encrypt.h message.c
+	cc -c message.c
+
+encrypt.o: encrypt.h encrypt.c
+	cc -c encrypt.c
diff --git a/C/HF/chap4/cryptic/ecat.c b/C/HF/chap4/cryptic/ecat.c
new file mode 100644
index 0000000..5266116
--- /dev/null
+++ b/C/HF/chap4/cryptic/ecat.c
@@ -0,0 +1,23 @@
+#include <stdio.h>
+#include "encrypt.h"
+
+int main(int argc, char **argv)
+{
+	FILE *fd;
+	char buf[80];
+
+	if (argc != 2)
+		return 1;
+
+	fd = fopen(argv[1], "r");
+
+	while (fgets(buf, 80, fd)) {
+		encrypt(buf);
+		printf("%s", buf);
+	}
+
+	printf("\n");
+	fclose(fd);
+
+	return 0;
+}
diff --git a/C/HF/chap4/cryptic/encrypt.c b/C/HF/chap4/cryptic/encrypt.c
new file mode 100644
index 0000000..128b1a4
--- /dev/null
+++ b/C/HF/chap4/cryptic/encrypt.c
@@ -0,0 +1,9 @@
+#include "encrypt.h"
+
+void encrypt(char *message)
+{
+	while (*message) {
+		*message = *message ^ 42;
+		message++;
+	}
+}
diff --git a/C/HF/chap4/cryptic/encrypt.h b/C/HF/chap4/cryptic/encrypt.h
new file mode 100644
index 0000000..7d5cf9d
--- /dev/null
+++ b/C/HF/chap4/cryptic/encrypt.h
@@ -0,0 +1,6 @@
+#ifndef ENCRYPT_H
+#define ENCRYPT_H
+
+void encrypt(char *m);
+
+#endif
diff --git a/C/HF/chap4/cryptic/message.c b/C/HF/chap4/cryptic/message.c
new file mode 100644
index 0000000..345774c
--- /dev/null
+++ b/C/HF/chap4/cryptic/message.c
@@ -0,0 +1,13 @@
+#include <stdio.h>
+#include "encrypt.h"
+
+int main(void)
+{
+	char msg[80];
+	while (fgets(msg, 80, stdin)) {
+		encrypt(msg);
+		printf("%s\n", msg);
+	}
+
+	return 0;
+}
diff --git a/C/HF/chap4/func_maze.c b/C/HF/chap4/func_maze.c
new file mode 100644
index 0000000..a65a3d1
--- /dev/null
+++ b/C/HF/chap4/func_maze.c
@@ -0,0 +1,12 @@
+#include <stdio.h>
+
+float amuze_me(void) {
+	return 3.9;
+}
+
+int main(void)
+{
+	int foo = amuze_me();
+	printf("%i\n", foo);
+	return 0;
+}
diff --git a/C/HF/chap4/lab1/moisture.c b/C/HF/chap4/lab1/moisture.c
new file mode 100644
index 0000000..349050f
--- /dev/null
+++ b/C/HF/chap4/lab1/moisture.c
@@ -0,0 +1,45 @@
+/* This works - tested on Tinkercad */
+#define THRESHOLD 800
+#define DRY 500
+
+#define LED 13
+
+setup(){
+	Serial.begin(9600);
+	pinMode(LED, OUTPUT);
+	digitalWrite(LED, LOW);
+}
+
+void blink_led(long interval) {
+	digitalWrite(LED, LOW);
+	delay(interval);
+	digitalWrite(LED, HIGH);
+}
+
+void led_on(void)
+{
+	if (digitalRead(LED) == LOW)
+		digitalWrite(LED, HIGH);
+}
+
+void led_off(void)
+{
+	if (digitalRead(LED) == HIGH) {
+		digitalWrite(LED, LOW);
+		Serial.println("Thank you, Seymour");
+	}
+}
+
+void loop(){
+	int moist = analogRead(1);
+	if (moist > THRESHOLD) {
+		led_off();
+		continue;
+	}
+
+	if (moist < DRY)
+		blink_led(500);
+	else
+		led_on();
+	Serial.println("Feed me!");
+}
diff --git a/C/HF/chap4/type.c b/C/HF/chap4/type.c
new file mode 100644
index 0000000..f63e134
--- /dev/null
+++ b/C/HF/chap4/type.c
@@ -0,0 +1,12 @@
+#include <stdio.h>
+#include <limits.h>
+#include <float.h>
+
+int main() {
+	printf("INT_MAX: %i\n", INT_MAX);
+	printf("INT_MIN: %i\n", INT_MIN);
+	printf("FLT_MAX: %f\n", DBL_MAX);
+	printf("FLT_MIN: %.600f\n", DBL_MIN);
+	printf("Int: %i\n", sizeof(size_t));
+	return 0;
+}