Before we begin

• Interrupt at any point
• Feedback is always welcome (too fast, too slow, too much, too little, too helpful, unhelpful)
• Office Hours are Wednesday 10:00AM-11:00AM at A4-157 or by email appointment [email protected]

Makefile

• Predefine commands to compile a project
• Has a target, dependencies and the command to run. Added perk, the command is only run if the dependencies have changed
• Can run multiple tasks in parallel with -j option

main: main.c
	gcc --std=c99 main.c -Wall -Wextra -Werror -o main

clean:
	rm -rf main
	
# FIXME: The target name must match the outputfile
# to take advantage of the caching system.
# also might help to run make with --debug option

Option Summary - Using the GNU Compiler Collection (GCC)

Pointers

A pointer is simply a variable that’s value is a memory address to another variable.

// TODO: small discussion on stack, heap, virtual memory, kernel space, 
// libc, and endianness
#include <stdio.h>

int main() {
  int a = 5;
	// while the convention is to write <int *p> 
	// I find it helpful to think of it as <int* p>
  int *pointer_to_a = &a;
  printf("%d %p %d",a, pointer_to_a, *pointer_to_a );
}

Structs

Structs offer a way to group values of same or different types together where each value can still retain its variable name (contrast this with arrays, where all values are of the same time and they are referred by their index, not name).

#include <stdio.h>
struct demo {
  int serial_number;
  int quantity;
};

int main() {
  struct demo demo1;
  demo1.quantity = 5;
  demo1.serial_number = 22;
  printf("%d", demo1.quantity);
}

• while struct values are accessed as demo.quantity if we have a struct demo* d1, the values are accessed as demo->quantity.

Linked List

• C does not have dynamically sized array. What if we want to add and remove values as we please during the program execution? (Bonus: When might a linked list be preferable over a vector or list?)