Course Introduction Introduction to Computer Systems Adapted from CMU course 15-213

1. Course IntroductionIntroduction to Computer Systems Adapted from CMU course 15-213 Instructor: Yuan Tang

2. Instructor • 唐渊 • yuantang@fudan.edu.cn • Phone # : 13917047105 • Make an appointment

3. Teaching Assistant • 王天豪 • 11302010005@fudan.edu.cn,15026687118 • 邬志罡 • 12302010008@fudan.edu.cn, 13585862607 • 李孟桐 • 12302010057@fudan.edu.cn, GoldenKnight@126.com,18818263415 • 曾虹驰 • 12302010055@fudan.edu.cn, 18818263645 • 郭悦 • 12302010083@fudan.edu.cn, 18818265520

4. Textbook and website • Randy Bryant and David O’Hallaron, • Computer Systems: A Programmer’s Perspective • 2nd Edition • Prentice Hall, 2011. • Brian Kernighan and Dennis Ritchie, • The C Programming Language, Second Edition • Prentice Hall, 1988 • http://ics.fudan.edu.cn

5. Grading • Exams(60%) • Mid term (20%) • Final (40%) • All exams are open books/open notes. • Labs (20%) • 4 labs(20%), (3-8% each) • On line exam for lab 2&3 (10%) • Home work(5%) • Scribing (15%)

6. Cheating • What is cheating? • Sharing code: by copying, retyping, looking at, or supplying a file • Coaching: helping your friend to write a lab, line by line • Copying code from previous course or from elsewhere on WWW • Only allowed to use code we supply, or from CS:APP website • What is NOT cheating? • Explaining how to use systems or tools • Helping others with high-level design issues • Penalty for cheating: • 0 credit for the lab • 0 chance to get A • Detection of cheating: • We do check • Our tools for doing this are much better than most cheaters think!

7. Theory Systems Curricular Structures • Three roles of science: • Observation • Conjecture • Test • Theory • How to model real world • Abstract concepts • How to reduce asymptotic bounds • System • How to run the real world • Concrete implementations • How to reduce constants

8. Carnegie Mellon Course Perspective • Most Systems Courses are Builder-Centric • Computer Architecture • Design pipelined processor in Verilog • Operating Systems • Implement large portions of operating system • Compilers • Write compiler for simple language • Networking • Implement and simulate network protocols

9. Carnegie Mellon Course Perspective (Cont.) • Our Course is Programmer-Centric • Purpose is to show how by knowing more about the underlying system, one can be more effective as a programmer • Enable you to • Write programs that are more reliable and efficient • Incorporate features that require hooks into OS • E.g., concurrency, signal handlers • Not just a course for dedicated hackers • We bring out the hidden hacker in everyone • Cover material in this course that you won’t see elsewhere

10. What’s covered by this course? • Assembly language • Programming in C • Compiler • Operating System • Computer Architecture • Performance Optimization • Networking • Concurrent programming

11. Carnegie Mellon Assembly Code Example • Time Stamp Counter • Special 64-bit register in Intel-compatible machines • Incremented every clock cycle • Read with rdtsc instruction • Application • Measure time (in clock cycles) required by procedure double t; start_counter(); P(); t = get_counter(); printf("P required %f clock cycles\n", t);

12. Carnegie Mellon Code to Read Counter • Write small amount of assembly code using GCC’s asm facility • Inserts assembly code into machine code generated by compiler static unsigned cyc_hi = 0; static unsigned cyc_lo = 0; /* Set *hi and *lo to the high and low order bits of the cycle counter. */ void access_counter(unsigned *hi, unsigned *lo) { asm("rdtsc; movl %%edx,%0; movl %%eax,%1" : "=r" (*hi), "=r" (*lo) : : "%edx", "%eax"); } GCC extended assembly syntax asm( assembler syntax : output operands /*optional */ : input operands /* optional */ : list of clobbered registers /* optional */ );

13. Operating Systems • 1960’s • IBM OS/360, Honeywell Multics, • Fernado Jose Corbató • IEEE Computer Pioneer Award, 1982 • ACM Turing Award, 1990

14. Operating Systems • Unix • Bell Lab, DEC PDP-7, 1969 • Ken Thompson, Dennis Ritchie, Doug Mcllroy, Joe Ossana • 1970 Brian Kernighandubbed the system “Unix” • Rewritten in C in 1973, announced in 1974 • BSD (UC, Berkeley), System V(Bell lab) • Solaris (Sun Microsystem) • Posix standard • Ken Thompson, Dennis Ritchie • ACM Turing Award, 1983

15. Linux • 1991, Linus Torvalds • Unix-like operating systems • 386(486)AT, bash(1.08), gcc(1.40) • Posix complaint version of Unix operating system • Available on a wide array of computers • From handheld devices to mainframe computers • wristwatch

16. GNU • Free software • Richard Stallman, 1984 • A complete Unix-like system with source code • An environment • All major components of a Unix operating system • Except for kernel

17. We have seen a bunch of Operating Systems

18. We have seen a bunch of Operating Systems

19. The C Programming Language • C was developed • in 1969 to 1973 • by Dennis Ritchie of Bell Laboratories. • The American National Standards Institute (ANSI) • ratified the ANSI C standard in 1989. • The standard defines • the C language • and a set of library functions known as the C standard library.

20. The C Programming Language • Kernighan and Ritchie describe ANSI C in their classic book • which is known affectionately as “K&R” . • describes the complete language and standard library, with numerous examples and exercises, in only 261 pages. • In Ritchie’s words, C is • quirky, • flawed, • and an enormous success. • Why the success?

21. The C Programming Language • C was closely tied with the Unix operating system • C was born for system programming • Small, simple, super-performance • Most of the Unix kernel, and all of its supporting tools and libraries, were written in C. • Widely taught and popular in in universities in the late 1970s and early 1980s • Portability • Lots of libraries

22. The C Programming Language • However, it is not perfect for all programmers and all situations • C pointer is dangerous • C is Not type-safe. • C is imperative

23. A tour of computer system • Information = bits + context • Text files • Binary files • The only thing that distinguish different data objects is the context in which we view them.

24. hello.c • hello.c: • 1 #include <stdio.h> • 2 • 3 int main() • 4 { • 5 printf(“hello, world\n”); • 6 }

25. The ASCII text representation of hello.c

26. The compilation system

27. Preprocessor Macro Substitution # 1 "a.c" # 1 "<built-in>" # 1 "<command-line>" # 1 "a.c" # 1 "b.h" 1 int j; # 2 "a.c" 2 main() { return 100 +j ; } • Obtain with command • gcc -E a.c • Source file a.i

28. Source Code and Assembly Code

29. Machine Code

31. Standardization of C • The original Bell Labs version of C • the 1st edition of the book K&R • The ANSI C standard in 1989 • The American National Standards Institute • Modify the way functions are declared • the 2nd edition of the book K&R • ISO C90 (The International Standards Organization)

32. Standardization of C • ISO C99 • Introduced some new data types • Provided support for text strings requiring characters not found in the English language • Gcc supporting • Unix> gcc -std=c99 prog.c • -ansiand -std=c89 have the same effect

33. Standardization of C

34. Why shall we understand how compilation system works? • Optimizing program performance void copyij(int src[2048][2048], int dst[2048][2048]) { int i,j; for (i = 0; i < 2048; i++) for (j = 0; j < 2048; j++) dst[i][j] = src[i][j]; } void copyji(int src[2048][2048], int dst[2048][2048]) { int i,j; for (j = 0; j < 2048; j++) for (i = 0; i < 2048; i++) dst[i][j] = src[i][j]; } 21 times slower(Pentium 4) • Hierarchical memory organization • Performance depends on access patterns • Including how step through multi-dimensional array

35. Why shall we understand how compilation system works? • Optimizing program performance • Understanding link-time errors • Linker cannot resolve a reference? • Static versus global variable? • Two global variables in different C files with the same name? • Order of listed library on the command line?

36. Why shall we understand how compilation system works? • Optimizing program performance • Understanding link-time errors • Avoiding security holes double fun(int i) { volatile double d[1] = {3.14}; volatile long int a[2]; a[i] = 1073741824; /* Possibly out of bounds */ return d[0]; }

37. Why shall we understand how compilation system works? • Avoiding security holes double fun(int i) { volatile double d[1] = {3.14}; volatile long int a[2]; a[i] = 1073741824; /* Possibly out of bounds */ return d[0]; } fun(0) => 3.14 fun(1) => 3.14 fun(2) =>3.14 fun(3) =>3.14 fun(4) =>segmentation fault • Result is architecture specific

38. Why shall we understand how compilation system works? • Avoiding security holes double fun(int i) { volatile double d[1] = {3.14}; volatile long int a[2]; a[i] = 1073741824; /* Possibly out of bounds */ return d[0]; } Explanation: Location accessed by fun(i)

39. Hardware organization of a system

40. Running the hello program

41. Running the hello program

42. Running the hello program

43. Storage hierarchy

44. The Operating System manages HW

45. Abstraction provided by OS • Files: • A sequence of bytes. • Unified API: UNIX I/O • Virtual memory: • Illusion of exclusive use of memory • Virtual address space • Process: • The OS’s abstraction for a running program • Concurrency, context switching, uni-processor system, multi-processor system

46. Process context switching • Process: • The OS’s abstraction for a running program • Concurrency, context switching, uni-processor system, multi-processor system

47. Virtual memory

48. Systems communicate with other systems using networks

49. Networking • Computers are connected by networks

50. Cloud • Computer Systems support the cloud computing Wireless Ethernet