CSC 2400: Computing Systems

Transcription

1 CSC 2400: Computing Systems Professor Mirela Damian 1 Introductions Mirela Damian (professor) Room 167A in the Mendel Science Building mirela.damian@villanova.edu Rusul Alsalihi (teaching assistant) Room 159 in the Mendel Science Building ralsalih@villanova.edu Programming assistants Room 292 in the Mendel Science Building 2

2 What do Computers Do? Do a survey on campus Numerous correct answers Computers Execute Instructions. That s all! 3 What Kind of Instructions? Strictly speaking, computers only understand machine language (binary machine code). 4

3 Hierarchy of Computer Languages Click an icon Press a key Verbal command Oracle / SQL MS Access Human interface languages Database languages SGML/ XML HTML Lisp / ML Shells / scripts Python Basic/ V Basic Java Pascal/Fortran ADA C++ C Mark up languages Interpreted languages High level compiled languages Assembly Low level el languages ages Machine Code 5 Course Goals: Look under the hood Help you learn what happens under the hood of computer systems Specifically, two downward tours Language levels tour High-level language (C) assembly language machine language g (IA-32) Service levels tour High-level language (C) standard libraries operating system (Linux) Reveal how abstractions are created 6

4 Course Goals: Why C? Q: Why C instead of Java? A: C facilitates language levels tour C is a lower-level language C is closely related to assembly language A: C facilitates service levels tour Linux is written in C 7 Course Goals: Why Linux? Q: Why Linux instead of Microsoft Windows? A: Linux is good for education and research Linux is open-source and well-specified A: Linux is good for programming Linux is a variant of Unix Unix has GNU, a rich open-source programming environment 8

5 Course Goals: Summary Help you to become a Power Programmer!!! 9 Resources: Books Textbook System Programming with C and Unix, Adam Hoover. Covers both language-level and system-level tours Some topics will be covered in more depth in class Lectures based on textbook and online material The textbook is mandatory Homework assignments are based on textbook and in class lectures. All homework due at start of class; not at the end of class. Additional materials posted on the class web site. 10

6 Resources: Programming Environment One Linux machine named felix. felix.csc.villanova.edu Any lab, or your own PC/MAC/Linux computer. Linux GNU Your Pgm felix SSH 11 Resources: Programming Environment Several Unix machines: degas, cezanne, tanner, picasso, rodin, cassatt, gauguin, g matisse. tanner.csc.villanova.edu Any lab, or your own PC/Mac/Linux Computer Unix GNU Your Pgm tanner rodin matisse SSH 12

7 Try to Log In Now Locate and invoke Secure Shell Client from the Start menu Click on the Quick Connect tab In the Host Name textbox, type in tanner.csc.villanova.edu In the User Name textbox, type in your username (the one the system administrator ed you) Click on Connect A text window with the shell prompt will be opened for you. This is a command line interface. You will interact with the Unix operating system by typing in commands at the shell prompt.try for example hostname The name of the machine (tanner) will be displayed. 13 Workload Distribution To use our Unix resources efficiently, from tanner connect arbitrarily to rodin or degas by typing in either ssh rodin ssh degas Too many students t working on one same machine can slow it down considerably. To log off, simply type in exit 14

8 Grading Assignments (45%) Pencil and paper p Clean, readable, working code On time (no late submission) First assignment is available now Exams (45%) Midterm Comprehensive final exam Class Participation (10%) No makeup assignments or exams Lecture attendance is mandatory 15 Programming g Assignments Start early to allow time for debugging. 16

9 Course Schedule Very generally Weeks Lectures 1-2 Introduction to C and Unix 3-7 Advanced C 7 Midterm exam Recess 8-11 Under the hood assembly language Thanksgiving Recess Under the hood Unix processes Dec. 19 Final exam, 6:00 8:30 pm See course web site for details 17 Any questions before we start? 18

10 C vs. Java: Design Goals Java design goals Support object-oriented programming Allow same program to be executed on multiple operating systems Support using computer networks Execute code from remote sources securely Adopt the good parts of other languages (esp. C and C++) Implications for Java Good for application-level programming High-level Virtual machine insulates programmer from underlying assembly language, machine language, hardware Portability over efficiency Security over efficiency Security over flexibility 19 C vs. Java: Design Goals C design goals Support structured programming Support development of the Unix OS and Unix tools As Unix became popular, so did C Implications for C Good for system-level programming But often used for application-level programming sometimes inappropriately Low-level Close to assembly language; close to machine language; close to hardware Efficiency over portability Efficiency over security Flexibility over security 20

11 C vs. Java: Design Goals Differences in design goals explain many differences between the languages C s Cs design goal explains many of its eccentricities We ll see examples throughout the course 21 C vs. Java: Overview Dennis Ritchie on the nature of C: C has always appealed to systems programmers who like the terse, concise manner in which powerful expressions can be coded. C allowed programmers to (while sacrificing portability) have direct access to many machine-level features that would otherwise require the use of assembly language. C is quirky, flawed, and an enormous success. While accidents of history surely helped, it evidently satisfied a need for a system implementation language efficient enough to displace assembly language, yet sufficiently abstract and fluent to describe algorithms and interactions in a wide variety of environments. 22

12 C vs. Java: Overview (cont.) Bad things you can do in C that you can t do in Java Shoot yourself in the foot (safety) Shoot others in the foot (security) Ignore wounds (error handling) Dangerous things you must do in C that you don t in Java Explicitly manage memory via malloc() and free() Good things you can do in C, but (more or less) must do in Java Program using the objected-oriented style Good things that you can t do in C but can do in Java Write completely portable code 23 C vs. Java: Details Remaining slides provide some details Suggestion: Use for future reference Slides covered briefly now 24

13 C vs. Java: Details (cont.) Overall Program Structure Java Hello.java: hello.c: public class Hello public static void #include <stdio.h> main(string[] args) int main(void) System.out.println( printf("hello Hello, world\n"); "Hello, world"); return 0; C Building % javac Hello.java % ls Hello.class Hello.java % % gcc hello.c % ls a.out hello.c % Running % java Hello Hello, world % %./a.out Hello, world % 25 C vs. Java: Details (cont.) Java C Character type char // 16-bit unicode char /* 8 bits */ Integral types byte short int long // 8 bits // 16 bits // 32 bits // 64 bits Floating gpoint float // 32 bits types double // 64 bits Logical type Generic pointer type boolean // no equivalent void* Constants final int MAX = 1000; (unsigned) char (unsigned) short (unsigned) int (unsigned) long float double long double /* no equivalent */ /* use integral type */ #define MAX 1000 const int MAX = 1000; enum MAX = 1000; 26

14 C vs. Java: Details (cont.) Arrays Java int [] a = new int [10]; float [][] b = new float [5][20]; C int a[10]; float b[5][20]; Array bound checking Pointer type Record type // run-time check /* no run-time check */ // Object reference is an // implicit pointer class Mine int x; float y; int *p; struct Mine int x; float y; 27 C vs. Java: Details (cont.) Java C Strings String concatenation String s1 = "Hello"; String s2 = new String("hello"); s1 + s2 s1 += s2 Logical ops &&,,! &&,,! char *s1 = "Hello"; char s2[6]; strcpy(s2, "hello"); #include <string.h> strcat(s1, s2); Relational ops =,!=, >, <, >=, <= =,!=, >, <, >=, <= Arithmetic ops +, -, *, /, %, unary - +, -, *, /, %, unary - Bitwise i ops >>, <<, >>>, &,, ^ >>, <<, &,, ^ Assignment ops =, *=, /=, +=, -=, <<=, >>=, >>>=, =, ^=, =, %= =, *=, /=, +=, -=, <<=, >>=, =, ^=, =, %= 28

15 C vs. Java: Details (cont.) if stmt switch stmt Java if (i < 0) statement1; else statement2; switch (i) case 1: break; case 2: break; default: C if (i < 0) statement1; else statement2; switch (i) case 1: break; case 2: break; default: goto stmt t // no equivalent goto SomeLabel; 29 C vs. Java: Details (cont.) Java C for stmt while stmt do-while stmt t for (int i=0; i<10; i++) statement; int i; for (i=0; i<10; i++) statement; while (i < 0) while (i < 0) statement; statement; do statement; ; while (i < 0) do statement; ; while (i < 0) continue stmt continue; continue; labeled continue stmt continue SomeLabel; /* no equivalent */ break stmt break; break; labeled break stmt break SomeLabel; /* no equivalent */ 30

16 C vs. Java: Details (cont.) Java C return stmt return 5; return; return 5; return; Compound stmt (alias block) statement1; statement2; statement1; statement2; Exceptions throw, try-catch-finally /* no equivalent */ Comments Method / function call /* comment */ // another kind f(x, y, z); someobject.f(x, y, z); SomeClass.f(x, y, z); /* comment */ f(x, y, z); 31 Example C Program File circle.c: #include <stdio.h> int main(void) /* Read a circle's radius from stdin, and compute and write its diameter and circumference to stdout. Return 0. */ int radius; int diam; double circum; printf("enter the circle's radius:\n"); scanf("%d", &radius); diam = 2 * radius; circum = * (double)diam; printf("a circle with radius %d has diameter %d\n", radius, diam); printf("and circumference %f.\n", circum); return 0; 32

17 Building and Running To build (preprocess, compile, assemble, and link): $ gcc circle.c o circle To run: $./circle Enter the circle's radius: 5 A circle with radius 5 has diameter 10 and circumference Typed by user 33 Steps in the Build Process To build one step at a time: Preprocess: circle.c circle.i Compile: circle.i circle.s Assemble: circle.s circle.o $ gcc E circle.c > circle.i $ gcc S circle.i $ gcc c circle.s $ gcc circle.o o circle Link: circle.o circle Why build one step at a time? Helpful for learning how to interpret error messages Permits partial builds (described later in course) 34

18 The Preprocessor s View File circle.c: #include <stdio.h> int main(void) Preprocessor directive Preprocessor replaces with contents of file /usr/include/stdio.h /* Read a circle's radius from stdin, and compute and write its diameter and circumference to stdout. Return 0. */ int radius; int diam; double circum; printf("enter the circle's radius:\n"); scanf("%d", &radius); diam = 2 * radius; circum = * (double)diam; printf("a circle with radius %d has diameter %d\n", radius, diam); printf("and circumference %f.\n", circum); return 0; Comment Preprocessor removes 35 Results of Preprocessing File circle.i: Declarations of printf(), scanf(), and other functions; compiler will have enough information to check subsequent function calls int printf(char*, ); int scanf(char*, ); int main(void) int radius; int diam; double circum; printf("enter the circle's radius:\n"); scanf("%d", &radius); diam = 2 * radius; circum = * (double)diam; printf("a circle with radius %d has diameter %d\n", radius, diam); printf("and circumference %f.\n", circum); return 0; Where are the DEFINITIONS of printf() and scanf()? 36

19 What is Wrong? #include <stdio.h> int SomeFunction(x); int main() int result; result = SomeFunction(5); return rn 0; int SomeFunction(int x) return x * x; 37 The Compiler s View File circle.i: int printf(char*, ); int scanf(char*, ); int main(void) int radius; int diam; double circum; printf("enter the circle's radius:\n"); scanf("%d", &radius); diam = 2 * radius; circum = * (double)diam; printf("a circle with radius %d has diameter %d\n", radius, diam); printf("and circumference %f.\n", circum); return 0; Function declarations Compiler notes return types and parameter types so it can check your function calls Function definition Compound statement alias block Return type of main() should be int 38

20 The Compiler s View (cont.) File circle.i: Declaration statements Must appear before any other kind of statement in block; variables must be declared int printf(char*, ); int scanf(char*, ); int main(void) int radius; before use int diam; double circum; printf("enter the circle's radius:\n"); scanf("%d", &radius); diam = 2 * radius; circum = * (double)diam; printf("a circle with radius %d has diameter %d\n", radius, diam); printf("and circumference %f.\n", circum); return 0; String constants Function call statements & ( address of ) operator Explained later in course, with pointers 39 What is Wrong? #include <stdio.h> int main() int sum; int i; for(int i = 1; i <= 10; i++) sum = sum + i; int fact; for(i = 1; i <= 10; i++) fact = fact * i; return 0; 40

21 The Compiler s View (cont.) File circle.i: int printf(char*, ); int scanf(char*, ); int main(void) Constant of type int Constant of type double int radius; int diam; double circum; printf("enter the circle's radius:\n"); scanf("%d", &radius); diam = 2 * radius; circum = * (double)diam; printf("a circle with radius %d has diameter %d\n", radius, diam); printf("and circumference %f.\n", circum); return 0; Expression statements Cast operator Unnecessary here, but good style to avoid mixed-type expressions 41 The Compiler s View (cont.) File circle.i: int printf(char*, ); int scanf(char*, ); int main(void) int radius; int diam; double circum; printf("enter the circle's radius:\n"); scanf("%d", &radius); Function call statements printf() can be called with 1 or more actual parameters diam = 2 * radius; circum = * (double)diam; printf("a circle with radius %d has diameter %d\n", radius, diam); printf("and circumference %f.\n", circum); return 0; Return statement Convention: 0 returned from main() means success; non-0 means failure 42

22 Results of Compiling File circle.s:.lc0:.lc1: main:.section.rodata.string "Enter the circle's radius:\n".string "%d".section.text.globl main.type pushl movl pushl call addl subl leal pushl pushl call %ebp %esp, %ebp $.LC0 printf $16, %esp $8, %esp -4(%ebp), %eax %eax $.LC1 scanf Assembly language Still missing definitions of printf() and scanf() 43 The Assembler s View File circle.s:.lc0:.lc1: main:.section.rodata.string "Enter the circle's radius:\n".string "%d".section.text.globl main.type pushl %ebp movl %esp, %ebp pushl $.LC0 call printf addl $16, %esp subl $8, %esp leal -4(%ebp), %eax pushl %eax pushl $.LC1 call scanf Assembly language Assembler translates assembly language into machine language Details provided in 2nd half of course 44

23 Results of Assembling File circle.o: Listing omitted Not human-readable Machine language Object file Still missing definitions of printf() and scanf() 45 The Linker s View File circle.o: Listing omitted Not human-readable Machine language The linker: Observes that Code in circle.o calls printf() and scanf() Code in circle.o does not define printf() or scanf() Fetches machine language definitions of printf() and scanf() from standard C library (/usr/lib/libc.a on your machine) Merges those definitions with circle.o to create 46

24 Results of Linking File circle: Listing omitted Not human-readable Machine language Complete executable binary file Run-Time View At run-time, memory devoted to program is divided into sections: TEXT RODATA DATA BSS HEAP TEXT (read-only) Stores machine language instructions RODATA(read-only) Stores read-only data (esp. strings) STACK(read/write) Stores local variables STACK Other sections described later in course 48

25 Run-Time View: Startup At program startup: TEXT contains machine language code defining main(), printf(), scanf(), etc. STACK is empty TEXT STACK RODATA main printf scanf RODATA contains every string ti constant tused in program; each is an array of characters, terminated with the null character ( \0 ) \0) Enter the circle s radius\n\0 %d\0 A circle with radius %d has diameter %d\n\0 and circumference %f.\n\0 49 Run-Time View: Declarations int radius; int diam; double circum; Computer allocates memory onto STACK for each local variable: 4 bytes for int, 8 bytes for double TEXT STACK RODATA main printf scanf circum diam radius Enter the circle s radius\n\0 %d\0 A circle with radius %d has diameter %d\n\0 and circumference %f.\n\0 50

26 Run-Time View: Writing a String printf("enter the circle's radius:\n"); Computer passes address containing E to printf(); printf() prints characters until it encounters \0 TEXT STACK RODATA main printf scanf circum diam radius Enter the circle s radius\n\0 %d\0 A circle with radius %d has diameter %d\n\0 and circumference %f.\n\0 51 Run-Time View: Reading an int scanf("%d", &radius); Computer passes address containing % to scanf(). scanf() waits for user input; user types 5; scanf() reads character(s), converts to decimal (d) constant, assigns to radius TEXT STACK RODATA main printf scanf circum diam radius 5 Enter the circle s radius\n\0 %d\0 A circle with radius %d has diameter %d\n\0 and circumference %f.\n\0 52

27 Run-Time View: Computing Results diam = 2 * radius; circum = * (double)diam; Computer uses radius to compute diam and circum TEXT STACK RODATA main printf scanf circum diam radius Enter the circle s radius\n\0 %d\0 A circle with radius %d has diameter %d\n\0 and circumference %f.\n\0 53 Run-Time View: Writing an int printf("a circle with radius %d has diameter %d\n", radius, diam); Computer passes address of A, value of radius, and value of diam to printf(). printf() prints until \0, replacing 1 st %d with character comprising 5, 2 nd %d with characters comprising 10 characters comprising 10 TEXT STACK RODATA main printf scanf circum diam radius Enter the circle s radius\n\0 %d\0 A circle with radius %d has diameter %d\n\0 and circumference %f.\n\0 54

28 Run-Time View: Writing a double printf("and circumference %f.\n", circum); TEXT STACK RODATA Computer passes address of a and value of circum to printf(). printf() prints until \0, replacing %f with characters comprising main printf scanf circum diam radius Enter the circle s radius\n\0 %d\0 A circle with radius %d has diameter %d\n\0 and circumference %f.\n\0 55 Run-Time View: Exiting return 0; Computer reclaims memory used by program; sections cease to exist 56

29 What Goes Where? int fact(n) int i, result=1; for(i = 1; i<=n; i++) result = result * i; return result; int main() int n; printf( Enter a value\n ); scanf( %d, &n); printf( The factorial of %d is %d, n, fact(n)); return 0; 57 What Goes Where? int fact(n) int i, ret=1; for(i = 1; i<=n; i++) ret = ret * i; return ret; TEXT STACK RODATA int main() int n; printf( Enter a value\n ); scanf( %d, &n); printf( The factorial of %d is %d, n,fact(n)); return 0; 58

30 Circle Program File circle.c: #include <stdio.h> int main(void) /* Read a circle's radius from stdin, and compute and write its diameter and circumference to stdout. Return 0. */ int radius; int diam; double circum; printf("enter the circle's radius:\n"); scanf("%d", &radius); diam = 2 * radius; circum = * (double)diam; printf("a circle with radius %d has diameter %d\n", radius, diam); printf("and circumference %f.\n", circum); return 0; 59 Toward Version 2 Problem (stylistic flaw): is a magic number Should give it a symbolic name to Increase code clarity Thereby increase code maintainability Solution: (In Java: final fields, final variables) In C: three approaches 60

31 Symbolic Constants: #define Approach 1: #define Preprocessor directive: replace START_STATE with 0 void f(void) #define START_ STATE 0 #define POSSIBLE_COMMENT_STATE 1 #define COMMENT_STATE 2 int state; state = START_STATE; state = COMMENT_STATE; Preprocessor replaces with 0 Preprocessor replaces with 2 61 Symbolic Constants: #define Approach 1 strengths Preprocessor does substitutions only for tokens int mystart_state; /* No replacement */ Preprocessor does not do substitutions within string constants printf("what is the START_STATE?\n"); /* No replacement */ Simple textual replacement; works for any type of data #define PI

32 Version 2 using #define #include <stdio.h> #define PI int main(void) /* Read a circle's radius from stdin, and compute and write its diameter and circumference to stdout. Return 0. */ int radius; int diam; double circum; printf("enter the circle's radius:\n"); scanf("%d", &radius); diam = 2 * radius; circum = PI * (double)diam; printf("a circle with radius %d has diameter %d\n", radius, diam); printf("and circumference %f.\n", circum); return 0; 63 Symbolic Constants: #define Approach 1 weaknesses Preprocessor does not respect context void f(void) #define MAX 1000 int MAX = 2000; Preprocessor replaces with 1000!!! Preprocessor does not respect scope void f(void) #define MAX 1000 void g(void) int MAX = 2000; Conventions: Use all uppercase for constants -- and only for constants Place #defines at beginning of file, not within function definitions 64

33 Symbolic Constants: const Approach 2: constant variables (oxymoron!!!) void f(void) const int START_STATE = 0; const int POSSIBLE_COMMENT_STATE STATE = 1; const int COMMENT_STATE = 2; int state; t state = START_STATE; state = COMMENT_STATE; Compiler does not allow value of START_STATE to change 65 Version 2 using const #include <stdio.h> const double PI = ; int main(void) /* Read a circle's radius from stdin, and compute and write its diameter and circumference to stdout. Return 0. */ int radius; int diam; double circum; printf("enter the circle's radius:\n"); scanf("%d", &radius); diam = 2 * radius; circum = PI * (double)diam; printf("a circle with radius %d has diameter %d\n", radius, diam); printf("and circumference %f.\n", circum); return 0; 66

34 Symbolic Constants: const Approach 2 strengths Works for any type of data const double PI = ; Handled by compiler, not preprocessor; p compiler respects context and scope Approach 2 weaknesses Does not work for array lengths (unlike C++) const int ARRAY_LENGTH = 10; int a[array_length]; /* Compiletime error */ 67 Symbolic Constants: enum Approach 3: Enumerations void f(void) enum State START_STATE, POSSIBLE_COMMENT_STATE, COMMENT_STATE, ; enum State state; state = START_STATE; state = COMMENT_STATE; Defines a variable named state to be of type enum State Defines a new type named enum State The constants of type enum State are START_STATE, 68

35 Symbolic Constants: enum Approach 3 note Enumerated constants are interchangeable with ints START_STATE is the same as 0 POSSIBLE_COMMENT_STATE is the same as 1 Etc. state = 0; /* Can assign int to enum. */ i = START_STATE; /* Can assign enum to int. */ 69 Symbolic Constants: enum Approach 3 strengths Can explicitly specify values for names enum State START_STATE = 5, POSSIBLE_COMMENT_STATE = 3, COMMENT_STATE = 4, ; Can omit type name, thus effectively giving names to int literals enum MAX_VALUE = 9999; int i = MAX_VALUE; Works when specifying array lengths enum ARRAY_LENGTH = 10; int a[array_length]; 70

36 Symbolic Constants: enum Approach 3 weakness Does not work for non-integral data types enum PI = ; /* Compiletime error */ 71 Symbolic Constant Style Rules In summary of symbolic constants Style rules: 1. Use enumerations to give symbolic names to integral constants 2. Use const variables to give symbolic names to non-integral constants 3. Use #define with all uppercase at beginning of file 72

37 Circle Program (Version 2) File circle.c (version 2): #include <stdio.h> int main(void) /* Read a circle's radius from stdin, and compute and write its diameter and circumference to stdout. Return 0. */ const double PI = ; int radius; int diam; double circum; printf("enter the circle's radius:\n"); scanf("%d", &radius); diam = 2 * radius; circum = PI * (double)diam; printf("a circle with radius %d has diameter %d\n", radius, diam); printf("and circumference %f.\n", circum); return 0; 73 Toward Version 3 Problem: Program does not handle bad user input $ circle Enter the circle's radius: abc User enters a non-number. How can the program detect that? What should the program do? 74

38 scanf 75 Detecting Bad User Input Solution Part 1: Detecting bad user input scanf() returns number of values successfully read Example: int returnvalue; returnvalue = scanf("%d", &i); if (returnvalue!= 1) /* Error */ Or, more succinctly: if (scanf("%d", &i)!= 1) /* Error */ Or, for more than one variable: if (scanf("%d%d", &i, &j)!= 2) /* Error */ 76

39 Reporting Failure to User Solution Part 2: Reporting failure to the user Stream Default Binding Purpose C Functions stdin Keyboard Normal input scanf( ); fscanf(stdin, ); stdout stderr Video screen Video screen Normal output Abnormal output printf( ); fprintf(stdout, ); fprintf(stderr, ); To report failure to user, should write a message to stderr 77 Reporting Failure to OS Solution Part 3: Reporting failure to the operating system Nature of Program Status Code that Program Completion Should Return to OS Successful 0 EXIT_SUCCESS (#defined in stdlib.h as 0) Unsuccessful EXIT_FAILURE (#defined in stdlib.h as???) To generate status code x, program should: Execute return x statement to return from main() function, or Call exit(x) to abort program System-dependent; Shell can examine status code on tanner, 1 Note: In main() function, return statement and exit() function have same effect In other functions, they have different effects 78

40 Circle Program (Version 3) #include <stdio.h> #include <stdlib.h> int main(void) /* Read a circle's radius from stdin, and compute and write its diameter and circumference to stdout. Return 0 if successful. */ const double PI = ; int radius; int diam; double circum; printf("enter the circle's radius:\n"); if (scanf("%d", &radius)!= 1) fprintf(stderr, "Error: Not a number\n"); exit(exit_failure); /* or: return EXIT_FAILURE; */ diam = 2 * radius; circum = PI * (double)diam; printf("a circle with radius %d has diameter %d\n", radius, diam); printf("and circumference %f.\n", circum); return 0; 79 Summary Simple C programs Program structure Defining symbolic constants #define, constant variables, enumerations Detecting and reporting failure The stderr stream The exit() function Functionality of the gcc command Preprocessor, compiler, assembler, linker Memory layout of a Linux process TEXT, RODATA, STACK sections (More sections DATA, BSS, HEAP later in the course) 80

41 Getting Started Check out course web site now Explore your computing environment Assignment posted on the website Reading Required: Chapters 2, 6.1, from the textbook Optional: Chapter 1 81