PowerPoint PresentationReview (1): 2’s Complement # “line”: N = 5Review (2): OverviewDisclaimerCompilation : OverviewCompilation : AdvantagesCompilation : DisadvantagesC vs. Java™ Overview (1/2)C vs. Java™ Overview (2/2)C Syntax: Variable DeclarationsC Syntax: True or False?C syntax : flow controlC Syntax: mainAdministrivia : You have a question?Administrivia : Near termAddress vs. ValuePointersSlide 20Slide 21Pointers and Parameter PassingSlide 23Slide 24Peer Instruction QuestionThe iMac G5 – where’d the computer go?Kilo, Mega, Giga, Tera, Peta, Exa, Zetta, YottaSlide 28Peer Instruction AnswerAnd in conclusion…CS 61C L03 Introduction to C (pt 1) (1)Garcia, Fall 2004 © UCBLecturer PSOE Dan Garciawww.cs.berkeley.edu/~ddgarciainst.eecs.berkeley.edu/~cs61c CS61C : Machine Structures Lecture 3 – Introduction to the C Programming Language 2004-09-03Pride of Cal Natalie Coughlinreturned after winning 5 Olympic medals (no US woman ever won more!). 15 hours from her degree! www.berkeley.eduCS 61C L03 Introduction to C (pt 1) (2)Garcia, Fall 2004 © UCBReview (1): 2’s Complement # “line”: N = 5•2 N-1 non-negatives •2 N-1 negatives•one zero•how many positives?0000000001000101111111110100000111110001012-1-2-15-1615......-311101-411100CS 61C L03 Introduction to C (pt 1) (3)Garcia, Fall 2004 © UCBReview (2): Overview•We represent “things” in computers as particular bit patterns: N bits 2N•Decimal for human calculations, binary for computers, hex to write binary more easily•1’s complement - mostly abandoned•2’s complement universal in computing: cannot avoid, so learn•Overflow: numbers ; computers finite, errors! 00000 00001 01111...111111111010000 ...00000 00001 01111...111111111010000 ...CS 61C L03 Introduction to C (pt 1) (4)Garcia, Fall 2004 © UCBDisclaimer•Important: You will not learn how to fully code in C in these lectures! You’ll still need your C reference for this course.•K&R is a must-have reference.-Check online for more sources.•“JAVA in a Nutshell,” O’Reilly. -Chapter 2, “How Java Differs from C”.CS 61C L03 Introduction to C (pt 1) (5)Garcia, Fall 2004 © UCBCompilation : OverviewC compilers take C and convert it into an architecture specific machine code (string of 1s and 0s).•Unlike Java which converts to architecture independent bytecode.•Unlike most Scheme environments which interpret the code.•Generally a 2 part process of compiling .c files to .o files, then linking the .o files into executablesCS 61C L03 Introduction to C (pt 1) (6)Garcia, Fall 2004 © UCBCompilation : Advantages•Great run-time performance: generally much faster than Scheme or Java for comparable code (because it optimizes for a given architecture)•OK compilation time: enhancements in compilation procedure (Makefiles) allow only modified files to be recompiledCS 61C L03 Introduction to C (pt 1) (7)Garcia, Fall 2004 © UCBCompilation : Disadvantages•All compiled files (including the executable) are architecture specific, depending on both the CPU type and the operating system.•Executable must be rebuilt on each new system.•Called “porting your code” to a new architecture.•The “changecompilerun [repeat]” iteration cycle is slowCS 61C L03 Introduction to C (pt 1) (8)Garcia, Fall 2004 © UCBC vs. Java™ Overview (1/2)Java•Object-oriented(OOP)•“Methods”•Class libraries of data structures•Automatic memory managementC•No built-in object abstraction. Data separate from methods.•“Functions”•C libraries are lower-level•Manualmemory management•PointersCS 61C L03 Introduction to C (pt 1) (9)Garcia, Fall 2004 © UCBC vs. Java™ Overview (2/2)Java•High memory overhead from class libraries•Relatively Slow•Arrays initialize to zero•Syntax: /*comment*/ // commentSystem.out.printC•Low memory overhead•Relatively Fast•Arrays initialize to garbage•Syntax:/*comment*/printfCS 61C L03 Introduction to C (pt 1) (10)Garcia, Fall 2004 © UCBC Syntax: Variable Declarations•Very similar to Java, but with a few minor but important differences•All variable declarations must go before they are used (at the beginning of the block). •A variable may be initialized in its declaration.•Examples of declarations:•correct:{inta=0,b=10;...•incorrect:for(inti=0;i<10;i++)CS 61C L03 Introduction to C (pt 1) (11)Garcia, Fall 2004 © UCBC Syntax: True or False?•What evaluates to FALSE in C?•0 (integer)•NULL (pointer: more on this later)•no such thing as a Boolean•What evaluates to TRUE in C?•everything else…•(same idea as in scheme: only #f is false, everything else is true!)CS 61C L03 Introduction to C (pt 1) (12)Garcia, Fall 2004 © UCBC syntax : flow control• Within a function, remarkably close to Java constructs in methods (shows its legacy) in terms of flow control•if-else•switch•whileandfor•do-whileCS 61C L03 Introduction to C (pt 1) (13)Garcia, Fall 2004 © UCBC Syntax: main•To get the main function to accept arguments, use this:intmain(intargc,char*argv[])•What does this mean?•argc will contain the number of strings on the command line (the executable counts as one, plus one for each argument).-Example: unix%sortmyFile•argv is a pointer to an array containing the arguments as strings (more on pointers later).CS 61C L03 Introduction to C (pt 1) (15)Garcia, Fall 2004 © UCBAdministrivia : You have a question?•Do not email Dan (& expect response)•Hundreds of emails in inbox•Email doesn’t scale to classes with 200+ students!•Tips on getting an answer to your question:•Ask a classmate•Ask Dan after or before lecture•The newsgroup, ucb.class.cs61c-Read it : Has your Q been answered already?-If not, ask it and check back•Ask TA in section, lab or OH•Ask Dan in OH•Ask Dan in lecture (if relevant to lecture)•Send your TA email•Send one of the two Head TAs email•Send Dan emailCS 61C L03 Introduction to C (pt 1) (16)Garcia, Fall 2004 © UCBAdministrivia : Near term•Monday is a holiday – have a good one•Upcoming lectures•C pointers and arrays in detail•HW•HW0 due in discussion next week•HW1 due this Wed @ 23:59 PST•HW2 due next Wed @ 23:59 PST•Reading•K&R Chapters 1-5 (lots, get started now!)•First quiz will be next WedCS 61C L03 Introduction to C (pt 1) (18)Garcia, Fall 2004 © UCBAddress vs. Value•Consider
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