add lab4,7,8 intro

11 lat temu · 120836eba7
--- a/lectures/lab4-intro-20131014.pdf
+++ b/lectures/lab4-intro-20131014.pdf
--- a/lectures/lab7-intro-20131031.pdf
+++ b/lectures/lab7-intro-20131031.pdf
--- a/lectures/lab8-intro-20131111.pdf
+++ b/lectures/lab8-intro-20131111.pdf