Add examples for presentation

.gitignore

@@ -0,0 +1 @@
+.~lock.*.pptx#

presentation/Makefile

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+SRC=example.c
+CC=gcc
+
+build: nopie pie
+
+nopie:
+	$(CC) -no-pie -o example.nopie example.c
+
+pie:
+	$(CC) -pie -o example.pie example.c

presentation/example.c

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+#include<stdio.h>
+
+void some_function() {
+  puts("Hello, world!\n");
+}
+
+int main() {
+  void (*function)() = &some_function;
+  printf("some_function is located at %p\n", function);
+  return 0;
+}