# CS 61C: Great Ideas in Computer Architecture C Pointers. Instructors: Vladimir Stojanovic & Nicholas Weaver

Size: px
Start display at page:

Transcription

1 CS 61C: Great Ideas in Computer Architecture C Pointers Instructors: Vladimir Stojanovic & Nicholas Weaver 1

2 Agenda Pointers Arrays in C 2

3 Address vs. Value Consider memory to be a single huge array Each cell of the array has an address associated with it Each cell also stores some value For addresses do we use signed or unsigned numbers? Negative address?! Don t confuse the address referring to a memory location with the value stored there

4 Pointers An address refers to a particular memory location; e.g., it points to a memory location Pointer: A variable that contains the address of a variable Location (address) name x y p 4

5 Pointer Syntax int *p; Tells compiler that variable p is address of an int p = &y; Tells compiler to assign address of y to p & called the address operator in this context z = *p; Tells compiler to assign value at address in p to z * called the dereference operator in this context 5

6 Creating and Using Pointers How to create a pointer: & operator: get address of a variable int *p, x; p? x? x = 3; p? x 3 p = &x; p x 3 How get a value pointed to? * (dereference operator): get the value that the pointer points to printf( p points to %d\n,*p); Note the * gets used 2 different ways in this example. In the declaration to indicate that p is going to be a pointer, and in the printf to get the value pointed to by p. 6

7 Using Pointer for Writes How to change a variable pointed to? Use the dereference operator * on left of assignment operator = p x 3 *p = 5; p x 5 7

8 Pointers and Parameter Passing Java and C pass parameters by value Procedure/function/method gets a copy of the parameter, so changing the copy cannot change the original void add_one (int x) { x = x + 1; } int y = 3; add_one(y); y remains equal to 3 8

9 Pointers and Parameter Passing How can we get a function to change the value held in a variable? void add_one (int *p) { *p = *p + 1; } int y = 3; add_one(&y); y is now equal to 4 9

10 Types of Pointers Pointers are used to point to any kind of data (int, char, a struct, etc.) Normally a pointer only points to one type (int, char, a struct, etc.). void * is a type that can point to anything (generic pointer) Use void * sparingly to help avoid program bugs, and security issues, and other bad things! 10

11 More C Pointer Dangers Declaring a pointer just allocates space to hold the pointer it does not allocate the thing being pointed to! Local variables in C are not initialized, they may contain anything (aka garbage ) What does the following code do? void f() { int *ptr; *ptr = 5; } 11

12 Pointers and Structures typedef struct { int x; int y; } Point; Point p1; Point p2; Point *paddr; /* dot notation */ int h = p1.x; p2.y = p1.y; /* arrow notation */ int h = paddr->x; int h = (*paddr).x; /* This works too */ p1 = p2; 12

13 Why use pointers? Pointers in C If we want to pass a large struct or array, it s easier / faster / etc. to pass a pointer than the whole thing In general, pointers allow cleaner, more compact code So what are the drawbacks? Pointers are probably the single largest source of bugs in C, so be careful anytime you deal with them Most problematic with dynamic memory management coming up next week Dangling references and memory leaks 13

14 Why Pointers in C? At time C was invented (early 1970s), compilers often didn t produce efficient code Computers 25,000 times faster today, compilers better C designed to let programmer say what they want code to do without compiler getting in way Even give compilers hints which registers to use! Today s compilers produce much better code, so may not need to use pointers in application code Low-level system code still needs low-level access via pointers 14

15 Video: Fun with Pointers sm_e 15

16 Clickers/Peer Instruction Time void foo(int *x, int *y) { int t; if ( *x > *y ) { t = *y; *y = *x; *x = t; } } int a=3, b=2, c=1; foo(&a, &b); foo(&b, &c); foo(&a, &b); printf("a=%d b=%d c=%d\n", a, b, c); Result is: A: a=3 b=2 c=1 B: a=1 b=2 c=3 C: a=1 b=3 c=2 D: a=3 b=3 c=3 E: a=1 b=1 c=1 16

17 Administrivia HW0 out, due: Sunday 11:59:59pm Give paper copy of mini-bio to your TA Get iclickers and register on bcourses! Participation points start today! People with university-related time conflict with lectures should contact the head GSIs. We will waive the clicker points but need to document conflict. Let head GSIs know about exam conflicts by the end of this week 17

18 Agenda Pointers Arrays in C 18

19 C Arrays Declaration: int ar[2]; declares a 2-element integer array: just a block of memory int ar[] = {795, 635}; declares and initializes a 2-element integer array 19

20 C Strings String in C is just an array of characters char string[] = "abc"; How do you tell how long a string is? Last character is followed by a 0 byte (aka null terminator ) int strlen(char s[]) { int n = 0; while (s[n]!= 0) n++; return n; } 20

21 Array Name / Pointer Duality Key Concept: Array variable is a pointer to the first (0 th ) element So, array variables almost identical to pointers char *string and char string[] are nearly identical declarations Differ in subtle ways: incrementing, declaration of filled arrays Consequences: ar is an array variable, but works like a pointer ar[0] is the same as *ar ar[2] is the same as *(ar+2) Can use pointer arithmetic to conveniently access arrays 21

22 C Arrays are Very Primitive An array in C does not know its own length, and its bounds are not checked! Consequence: We can accidentally access off the end of an array Consequence: We must pass the array and its size to any procedure that is going to manipulate it Segmentation faults and bus errors: These are VERY difficult to find; be careful! (You ll learn how to debug these in lab) But also fun to exploit: Stack overflow exploit, maliciously write off the end of an array on the stack Heap overflow exploit, maliciously write off the end of an array on the heap 22

23 Use Defined Constants Array size n; want to access from 0 to n-1, so you should use counter AND utilize a variable for declaration & incrementation Bad pattern int i, ar[10]; for(i = 0; i < 10; i++){... } Better pattern const int ARRAY_SIZE = 10; int i, a[array_size]; for(i = 0; i < ARRAY_SIZE; i++){... } SINGLE SOURCE OF TRUTH You re utilizing indirection and avoiding maintaining two copies of the number 10 DRY: Don t Repeat Yourself And don t forget the < rather than <=: When Nick took 60c, he lost a day to a segfault in a malloc called by printf on large inputs : Had a <= rather than a < in a single array initialization! 23

24 Pointing to Different Size Objects Modern machines are byte-addressable Hardware s memory composed of 8-bit storage cells, each has a unique address A C pointer is just abstracted memory address Type declaration tells compiler how many bytes to fetch on each access through pointer E.g., 32-bit integer stored in 4 consecutive 8-bit bytes short *y int *x char *z Byte address 16-bit short stored in two bytes 32-bit integer stored in four bytes 8-bit character stored in one byte 24

25 sizeof() operator sizeof(type) returns number of bytes in object But number of bits in a byte is not standardized In olden times, when dragons roamed the earth, bytes could be 5, 6, 7, 9 bits long By definition, sizeof(char)==1 Can take sizeof(arg), or sizeof(structtype) We ll see more of sizeof when we look at dynamic memory management 25

26 Pointer Arithmetic pointer + number e.g., pointer + 1 pointer number adds 1 something to a pointer char *p; char a; char b; int *p; int a; int b; p = &a; p += 1; In each, p now points to b (Assuming compiler doesn t reorder variables in memory. Never code like this!!!!) p = &a; p += 1; Adds 1*sizeof(char) to the memory address Adds 1*sizeof(int) to the memory address Pointer arithmetic should be used cautiously 26

27 Changing a Pointer Argument? What if want function to change a pointer? What gets printed? void inc_ptr(int *p) { p = p + 1; } A q *q = 50 int A[3] = {50, 60, 70}; int* q = A; inc_ptr( q); printf( *q = %d\n, *q);

28 Pointer to a Pointer Solution! Pass a pointer to a pointer, declared as **h Now what gets printed? void inc_ptr(int **h) { *h = *h + 1; } A q *q = 60 q int A[3] = {50, 60, 70}; int* q = A; inc_ptr(&q); printf( *q = %d\n, *q);

29 And In Conclusion, All data is in memory Each memory location has an address to use to refer to it and a value stored in it Pointer is a C version (abstraction) of a data address * follows a pointer to its value & gets the address of a value Arrays and strings are implemented as variations on pointers C is an efficient language, but leaves safety to the programmer Variables not automatically initialized Use pointers with care: they are a common source of bugs in programs 29

### Intro to C: Pointers and Arrays

Lecture 4 Computer Science 61C Spring 2017 January 25th, 2017 Intro to C: Pointers and Arrays 1 Administrivia Teaching Assistants: Let s try that again. Lectures are recorded. Waitlist/Concurrent Enrollment

### Pointers, Arrays, Memory: AKA the cause of those Segfaults

Computer Science 61C Spring 2018 Wawrzynek and Weaver Pointers, Arrays, Memory: AKA the cause of those F@#)(#@*( Segfaults 1 Agenda Computer Science 61C Spring 2018 Pointers Arrays in C Memory Allocation

### CS 61C: Great Ideas in Computer Architecture Introduc)on to C, Part II

CS 61C: Great Ideas in Computer Architecture Introduc)on to C, Part II Instructors: Krste Asanovic & Vladimir Stojanovic h>p://inst.eecs.berkeley.edu/~cs61c/sp15 1 Review: Components of a Computer Processor

### Agenda. Peer Instruction Question 1. Peer Instruction Answer 1. Peer Instruction Question 2 6/22/2011

CS 61C: Great Ideas in Computer Architecture (Machine Structures) Introduction to C (Part II) Instructors: Randy H. Katz David A. Patterson http://inst.eecs.berkeley.edu/~cs61c/sp11 Spring 2011 -- Lecture

### Arrays and Memory Management

Arrays and Memory Management 1 Pointing to Different Size Objects Modern machines are byte-addressable Hardware s memory composed of 8-bit storage cells, each has a unique address A C pointer is just abstracted

### CS 61C: Great Ideas in Computer Architecture Introduc)on to C, Part II. Control. Consider memory to be a single huge array

Review: Components of a Computer CS 61C: Great Ideas in Computer Architecture Introduc)on to C, Part II Processor Control Datapath PC Enable? Read/Write Address Memory Program Bytes Input Instructors:

### Agenda. Address vs. Value Consider memory to be a single huge array. Review. Pointer Syntax. Pointers 9/9/12

Agenda CS 61C: Great Ideas in Computer Architecture Introduc;on to C, Part II Instructors: Krste Asanovic Randy H. Katz hep://inst.eecs.berkeley.edu/~cs61c/f12 Review Pointers Administrivia Arrays Technology

### CS 61C: Great Ideas in Computer Architecture. Lecture 3: Pointers. Bernhard Boser & Randy Katz

CS 61C: Great Ideas in Computer Architecture Lecture 3: Pointers Bernhard Boser & Randy Katz http://inst.eecs.berkeley.edu/~cs61c Agenda Pointers in C Arrays in C This is not on the test Pointer arithmetic

### CS 102 Computer Architecture. Lecture 2: Introduction to C, Part I. Instructor: Sören Schwertfeger.

CS 102 Computer Architecture Lecture 2: Introduction to C, Part I Instructor: Sören Schwertfeger http://shtech.org/courses/ca/ School of Information Science and Technology SIST ShanghaiTech University

### CS 61C: Great Ideas in Computer Architecture. Lecture 3: Pointers. Krste Asanović & Randy Katz

CS 61C: Great Ideas in Computer Architecture Lecture 3: Pointers Krste Asanović & Randy Katz http://inst.eecs.berkeley.edu/~cs61c Agenda Pointers in C Arrays in C This is not on the test Pointer arithmetic

### HW1 due Monday by 9:30am Assignment online, submission details to come

inst.eecs.berkeley.edu/~cs61c CS61CL : Machine Structures Lecture #2 - C Pointers and Arrays Administrivia Buggy Start Lab schedule, lab machines, HW0 due tomorrow in lab 2009-06-24 HW1 due Monday by 9:30am

### Agenda. Components of a Computer. Computer Memory Type Name Addr Value. Pointer Type. Pointers. CS 61C: Great Ideas in Computer Architecture

CS 61C: Great Ideas in Computer Architecture Krste Asanović & Randy Katz http://inst.eecs.berkeley.edu/~cs61c And in Conclusion, 2 Processor Control Datapath Components of a Computer PC Registers Arithmetic

### CS 61C: Great Ideas in Computer Architecture. C Arrays, Strings, More Pointers

CS 61C: Great Ideas in Computer Architecture C Arrays, Strings, More Pointers Instructor: Justin Hsia 6/20/2012 Summer 2012 Lecture #3 1 Review of Last Lecture C Basics Variables, Functions, Flow Control,

### CS61C : Machine Structures

inst.eecs.berkeley.edu/~cs61c CS61C : Machine Structures Lecture #3 C Strings, Arrays, & Malloc 2007-06-27 Scott Beamer, Instructor Sun announces new supercomputer: Sun Constellation CS61C L3 C Pointers

### CS61C : Machine Structures

inst.eecs.berkeley.edu/~cs61c CS61C : Machine Structures Lecture 4 Introduction to C (pt 2) 2014-09-08!!!Senior Lecturer SOE Dan Garcia!!!www.cs.berkeley.edu/~ddgarcia! C most popular! TIOBE programming

### CS61C Machine Structures. Lecture 4 C Pointers and Arrays. 1/25/2006 John Wawrzynek. www-inst.eecs.berkeley.edu/~cs61c/

CS61C Machine Structures Lecture 4 C Pointers and Arrays 1/25/2006 John Wawrzynek (www.cs.berkeley.edu/~johnw) www-inst.eecs.berkeley.edu/~cs61c/ CS 61C L04 C Pointers (1) Common C Error There is a difference

### Number Review. Lecture #3 More C intro, C Strings, Arrays, & Malloc Variables. Clarification about counting down

CS61C L3 C Pointers (1) inst.eecs.berkeley.edu/~cs61c CS61C : Machine Structures Lecture #3 More C intro, C Strings, Arrays, & Malloc Albert Chae Instructor 2008-06-25 Number Review Sign and magnitude

### CS61C : Machine Structures

inst.eecs.berkeley.edu/~cs61c CS61C : Machine Structures Lecture 4 C Pointers 2004-09-08 Lecturer PSOE Dan Garcia www.cs.berkeley.edu/~ddgarcia Cal flies over Air Force We re ranked 13 th in the US and

### ECE 15B COMPUTER ORGANIZATION

ECE 15B COMPUTER ORGANIZATION Lecture 13 Strings, Lists & Stacks Announcements HW #3 Due next Friday, May 15 at 5:00 PM in HFH Project #2 Due May 29 at 5:00 PM Project #3 Assigned next Thursday, May 19

### Two s Complement Review. Two s Complement Review. Agenda. Agenda 6/21/2011

Two s Complement Review CS 61C: Great Ideas in Computer Architecture (Machine Structures) Introduction to C (Part I) Instructor: Michael Greenbaum http://inst.eecs.berkeley.edu/~cs61c/su11 Suppose we had

### Review: C Strings. A string in C is just an array of characters. Lecture #4 C Strings, Arrays, & Malloc

CS61C L4 C Pointers (1) inst.eecs.berkeley.edu/~cs61c CS61C : Machine Structures Lecture #4 C Strings, Arrays, & Malloc Albert Chae Instructor 2008-06-26 Review: C Strings A string in C is just an array

### CS 61c: Great Ideas in Computer Architecture

Arrays, Strings, and Some More Pointers June 24, 2014 Review of Last Lecture C Basics Variables, functioss, control flow, types, structs Only 0 and NULL evaluate to false Pointers hold addresses Address

### Instructor: Randy H. Katz hbp://inst.eecs.berkeley.edu/~cs61c/fa13. Fall Lecture #4. Agenda

CS 61C: Great Ideas in Computer Architecture Introduc)on to C, Part II Instructor: Randy H. Katz hbp://inst.eecs.berkeley.edu/~cs61c/fa13 9/10/13 Fall 2013 - - Lecture #4 1 Agenda Pointers and Arrays Administrivia

### CS 61C: Great Ideas in Computer Architecture Lecture 2: Introduction to C, Part I

CS 61C: Great Ideas in Computer Architecture Lecture 2: Introduction to C, Part I Instructors: Vladimir Stojanovic & John Wawrzynek http://inst.eecs.berkeley.edu/~cs61c/ 1 Agenda Compile vs. Interpret

### C Arrays, Strings, More Pointers Instructor: Steven Ho

C Arrays, Strings, More Pointers Instructor: Steven Ho Review of Last Lecture C Basics Variables, Functions, Flow Control, Types, and Structs Only 0 and NULL evaluate to FALSE Pointers hold addresses Address

### CS 61C: Great Ideas in Computer Architecture Introduction to C

CS 61C: Great Ideas in Computer Architecture Introduction to C Instructors: Vladimir Stojanovic & Nicholas Weaver http://inst.eecs.berkeley.edu/~cs61c/ 1 Agenda C vs. Java vs. Python Quick Start Introduction

### CS61C : Machine Structures

inst.eecs.berkeley.edu/~cs61c CS61C : Machine Structures Lecture 5 C Memory Management Lecturer PSOE Dan Garcia www.cs.berkeley.edu/~ddgarcia CS 61C L04 C Structures, Memory Management (1) 2004-09-10 Barry

### More C Pointer Dangers

CS61C L04 Introduction to C (pt 2) (1) inst.eecs.berkeley.edu/~cs61c CS61C : Machine Structures Must-see talk Thu 4-5pm @ Sibley by Turing Award winner Fran Allen: The Challenge of Multi-Cores: Think Sequential,

### Review! * follows a pointer to its value! & gets the address of a variable! Pearce, Summer 2010 UCB! ! int x = 1000; Pearce, Summer 2010 UCB!

CS61C L03 Introduction to C (pt 2) (1)! inst.eecs.berkeley.edu/~cs61c CS61C : Machine Structures Lecture 3 Introduction to C (pt 2) 2010-06-23!!!Instructor Paul Pearce! The typical! development cycle!

### CS61C : Machine Structures

inst.eecs.berkeley.edu/~cs61c CS61C : Machine Structures Lecture 3 Introduction to C (pt 2) 2010-06-23! C help session: Tonight 7:00-9:00pm @ 306 Soda!!!Instructor Paul Pearce! The typical! development

### CS61C Machine Structures. Lecture 5 C Structs & Memory Mangement. 1/27/2006 John Wawrzynek. www-inst.eecs.berkeley.edu/~cs61c/

CS61C Machine Structures Lecture 5 C Structs & Memory Mangement 1/27/2006 John Wawrzynek (www.cs.berkeley.edu/~johnw) www-inst.eecs.berkeley.edu/~cs61c/ CS 61C L05 C Structs (1) C String Standard Functions

### CS61C Machine Structures. Lecture 4 C Structs & Memory Management. 9/5/2007 John Wawrzynek. www-inst.eecs.berkeley.edu/~cs61c/

CS61C Machine Structures Lecture 4 C Structs & Memory Management 9/5/2007 John Wawrzynek (www.cs.berkeley.edu/~johnw) www-inst.eecs.berkeley.edu/~cs61c/ CS 61C L04 C Structs (1) C String Standard Functions

### CS61C Machine Structures. Lecture 3 Introduction to the C Programming Language. 1/23/2006 John Wawrzynek. www-inst.eecs.berkeley.

CS61C Machine Structures Lecture 3 Introduction to the C Programming Language 1/23/2006 John Wawrzynek (www.cs.berkeley.edu/~johnw) www-inst.eecs.berkeley.edu/~cs61c/ CS 61C L03 Introduction to C (1) Administrivia

### How about them A s!! Go Oaktown!! CS61C - Machine Structures. Lecture 4 C Structures Memory Management Dan Garcia.

How about them A s!! Go Oaktown!! CS61C - Machine Structures Lecture 4 C Structures Memory Management 2002-09-05 Dan Garcia (www.cs.berkeley.edu/~ddgarcia) Dave Patterson (www.cs.berkeley.edu/~patterson)

### Arrays and Pointers in C. Alan L. Cox

Arrays and Pointers in C Alan L. Cox alc@rice.edu Objectives Be able to use arrays, pointers, and strings in C programs Be able to explain the representation of these data types at the machine level, including

### CS61C : Machine Structures

inst.eecs.berkeley.edu/~cs61c CS61C : Machine Structures Lecture 5 C Memory Management Lecturer PSOE Dan Garcia www.cs.berkeley.edu/~ddgarcia CS61C L05 C Structures, Memory Management (1) 2005-01-28 The

### IT 252 Computer Organization and Architecture Introduction to the C Programming Language

IT 252 Computer Organization and Architecture Introduction to the C Programming Language Chia-Chi Teng Administrivia : You have a question? Tips on getting an answer to your question: Ask a classmate Catch

### Lecture 4: Outline. Arrays. I. Pointers II. III. Pointer arithmetic IV. Strings

Lecture 4: Outline I. Pointers A. Accessing data objects using pointers B. Type casting with pointers C. Difference with Java references D. Pointer pitfalls E. Use case II. Arrays A. Representation in

### Lecture 5: Outline. I. Multi- dimensional arrays II. Multi- level arrays III. Structures IV. Data alignment V. Linked Lists

Lecture 5: Outline I. Multi- dimensional arrays II. Multi- level arrays III. Structures IV. Data alignment V. Linked Lists Multidimensional arrays: 2D Declaration int a[3][4]; /*Conceptually 2D matrix

### Topics Introduction to Microprocessors

Topics 22440 Introduction to Microprocessors C-Language Review (I) Important: : You will not learn how to code in C in this one lecture! You ll still need some sort of C reference. C Syntax Important Tidits

### Has there been an update to ANSI C? Lecture #3 C Pointers Yes! It s called the C99 or C9x std

CS61C L3 C Pointers (1) inst.eecs.berkeley.edu/~cs61c CS61C : Machine Structures Lecture #3 C Pointers 2005-09-07 There is one handout today at the front and back of the room! Lecturer PSOE, new dad Dan

### In Java we have the keyword null, which is the value of an uninitialized reference type

+ More on Pointers + Null pointers In Java we have the keyword null, which is the value of an uninitialized reference type In C we sometimes use NULL, but its just a macro for the integer 0 Pointers are

### CS 61c: Great Ideas in Computer Architecture

Introduction to C, Pointers June 24, 2014 Review of Last Lecture Six Great Ideas in Computer Architecture Number Representation Bits can represent anything! n bits can represent up to 2 n things Unsigned,

### Numbers: positional notation. CS61C Machine Structures. Faux Midterm Review Jaein Jeong Cheng Tien Ee. www-inst.eecs.berkeley.

CS 61C Faux Midterm Review (1) CS61C Machine Structures Faux Midterm Review 2002-09-29 Jaein Jeong Cheng Tien Ee www-inst.eecs.berkeley.edu/~cs61c/ Numbers: positional notation Number Base B B symbols

### Intermediate Programming, Spring 2017*

600.120 Intermediate Programming, Spring 2017* Misha Kazhdan *Much of the code in these examples is not commented because it would otherwise not fit on the slides. This is bad coding practice in general

### CS61C : Machine Structures

Get your clickers ready...! inst.eecs.berkeley.edu/~cs61c CS61C : Machine Structures Lecture 3 Introduction to the C Programming Language (pt 1) 2013-01-28! Hello to Nishant Varma watching from India!!!Senior

### First of all, it is a variable, just like other variables you studied

Pointers: Basics What is a pointer? First of all, it is a variable, just like other variables you studied So it has type, storage etc. Difference: it can only store the address (rather than the value)

### Processor. Lecture #2 Number Rep & Intro to C classic components of all computers Control Datapath Memory Input Output

CS61C L2 Number Representation & Introduction to C (1) insteecsberkeleyedu/~cs61c CS61C : Machine Structures Lecture #2 Number Rep & Intro to C Scott Beamer Instructor 2007-06-26 Review Continued rapid

### CMSC 313 COMPUTER ORGANIZATION & ASSEMBLY LANGUAGE PROGRAMMING LECTURE 13, SPRING 2013

CMSC 313 COMPUTER ORGANIZATION & ASSEMBLY LANGUAGE PROGRAMMING LECTURE 13, SPRING 2013 TOPICS TODAY Reminder: MIDTERM EXAM on THURSDAY Pointer Basics Pointers & Arrays Pointers & Strings Pointers & Structs

### CS61C : Machine Structures

inst.eecs.berkeley.edu/~cs61c CS61C : Machine Structures Lecture 4 Introduction to C (pt 2) C Pointers CS61C L03 Introduction to C (pt 2) (1) 2006-09-06 Lecturer SOE Dan Garcia www.cs.berkeley.edu/~ddgarcia

### CS 31: Intro to Systems Pointers and Memory. Kevin Webb Swarthmore College October 2, 2018

CS 31: Intro to Systems Pointers and Memory Kevin Webb Swarthmore College October 2, 2018 Overview How to reference the location of a variable in memory Where variables are placed in memory How to make

### CS61C : Machine Structures

Get your clickers ready...! inst.eecs.berkeley.edu/~cs61c CS61C : Machine Structures Lecture 3 Introduction to the C Programming Language (pt 1)!!Senior Lecturer SOE Dan Garcia!!!www.cs.berkeley.edu/~ddgarcia

### Lecture 14. No in-class files today. Homework 7 (due on Wednesday) and Project 3 (due in 10 days) posted. Questions?

Lecture 14 No in-class files today. Homework 7 (due on Wednesday) and Project 3 (due in 10 days) posted. Questions? Friday, February 11 CS 215 Fundamentals of Programming II - Lecture 14 1 Outline Static

### Reference slides! C Strings! A string in C is just an array of characters.!!!char string[] = "abc";! How do you tell how long a string is?!

CS61C L04 Introduction to C (pt 2) (1)! Reference slides! C Strings! You ARE responsible for the material on these slides (they re just taken from the reading anyway). These were the slides that generated

### CS61C : Machine Structures

inst.eecs.berkeley.edu/~cs61c CS61C : Machine Structures Lecture 2 Introduction to the C Programming Language (pt 1) 2010-06-22!!!Instructor Paul Pearce! There is a handout at the front of the room! Please

### Lecture 2: C Programm

0 3 E CS 1 Lecture 2: C Programm ing C Programming Procedural thought process No built in object abstractions data separate from methods/functions Low memory overhead compared to Java No overhead of classes

### CS 110 Computer Architecture. Lecture 4: Introduction to C, Part III. Instructor: Sören Schwertfeger.

CS 110 Computer Architecture Lecture 4: Introduction to C, Part III Instructor: Sören Schwertfeger http://shtech.org/courses/ca/ School of Information Science and Technology SIST ShanghaiTech University

### Reference slides! Garcia, Fall 2011 UCB! CS61C L04 Introduction to C (pt 2) (1)!

Reference slides! You ARE responsible for the material on these slides (they re just taken from the reading anyway). These were the slides that generated the fewest questions in years past (i.e., those

### CS 61C: Great Ideas in Computer Architecture Introduction to C, Part III

CS 61C: Great Ideas in Computer Architecture Introduction to C, Part III Instructors: John Wawrzynek & Vladimir Stojanovic http://inst.eecs.berkeley.edu/~cs61c/fa15 1 Review, Last Lecture Pointers are

### C++ for Java Programmers

Basics all Finished! Everything we have covered so far: Lecture 5 Operators Variables Arrays Null Terminated Strings Structs Functions 1 2 45 mins of pure fun Introduction Today: Pointers Pointers Even

### CS61C : Machine Structures

inst.eecs.berkeley.edu/~cs61c CS61C : Machine Structures Lecture 3 Introduction to the C Programming Language (pt 1)!!Lecturer SOE Dan Garcia!!!www.cs.berkeley.edu/~ddgarcia CS61C L03 Introduction to C

### Announcements. assign0 due tonight. Labs start this week. No late submissions. Very helpful for assign1

Announcements assign due tonight No late submissions Labs start this week Very helpful for assign1 Goals for Today Pointer operators Allocating memory in the heap malloc and free Arrays and pointer arithmetic

### Class Information ANNOUCEMENTS

Class Information ANNOUCEMENTS Third homework due TODAY at 11:59pm. Extension? First project has been posted, due Monday October 23, 11:59pm. Midterm exam: Friday, October 27, in class. Don t forget to

### C: Introduction, Pointers Instructors: Steven Ho, Nick Riasanovsky

C: Introduction, Pointers Instructors: Steven Ho, Nick Riasanovsky Overflow Overflow is when the result of an arithmetic operation can t be represented by the (FINITE) hardware bits i.e. the result is

### CS61C : Machine Structures

inst.eecs.berkeley.edu/~cs61c CS61C : Machine Structures Lecture #4 C Memory Management 2007-06-28 Scott Beamer, Instructor iphone Comes out Tomorrow CS61C L4 C Memory Management (1) www.apple.com/iphone

### C: Pointers. C: Pointers. Department of Computer Science College of Engineering Boise State University. September 11, /21

Department of Computer Science College of Engineering Boise State University September 11, 2017 1/21 Pointers A pointer is a variable that stores the address of another variable. Pointers are similar to

### Number review... Lecture 3 Introduction to the C Programming Language (pt 1) Has there been an update to ANSI C?

CS61C L03 Introduction to C (pt 1) (1) inst.eecs.berkeley.edu/~cs61c CS61C : Machine Structures Lecture 3 Introduction to the C Programming Language (pt 1) 2008-01-28 Lecturer SOE Dan Garcia Hello to Dev

### a data type is Types

Pointers Class 2 a data type is Types Types a data type is a set of values a set of operations defined on those values in C++ (and most languages) there are two flavors of types primitive or fundamental

### CMSC 313 COMPUTER ORGANIZATION & ASSEMBLY LANGUAGE PROGRAMMING LECTURE 13, FALL 2012

CMSC 313 COMPUTER ORGANIZATION & ASSEMBLY LANGUAGE PROGRAMMING LECTURE 13, FALL 2012 TOPICS TODAY Project 5 Pointer Basics Pointers and Arrays Pointers and Strings POINTER BASICS Java Reference In Java,

### CS 11 C track: lecture 5

CS 11 C track: lecture 5 Last week: pointers This week: Pointer arithmetic Arrays and pointers Dynamic memory allocation The stack and the heap Pointers (from last week) Address: location where data stored

### Physics 2660: Fundamentals of Scientific Computing. Lecture 3 Instructor: Prof. Chris Neu

Physics 2660: Fundamentals of Scientific Computing Lecture 3 Instructor: Prof. Chris Neu (chris.neu@virginia.edu) Announcements Weekly readings will be assigned and available through the class wiki home

### CS 61C: Great Ideas in Computer Architecture C Memory Management, Usage Models

CS 61C: Great Ideas in Computer Architecture C Memory Management, Usage Models Instructors: Nicholas Weaver & Vladimir Stojanovic http://inst.eecs.berkeley.edu/~cs61c/sp16 1 Pointer Ninjitsu: Pointers

### CS Programming In C

CS 24000 - Programming In C Week 16: Review Zhiyuan Li Department of Computer Science Purdue University, USA This has been quite a journey Congratulation to all students who have worked hard in honest

### Number Representation & I See The C

Number Representation & I See The C 1 Signed Integers and Two s-complement Representation Signed integers in C; want ½ numbers 0, and want one 0 Two s complement treats 0 as positive,

### CS107 Handout 08 Spring 2007 April 9, 2007 The Ins and Outs of C Arrays

CS107 Handout 08 Spring 2007 April 9, 2007 The Ins and Outs of C Arrays C Arrays This handout was written by Nick Parlante and Julie Zelenski. As you recall, a C array is formed by laying out all the elements

### 3/22/2016. Pointer Basics. What is a pointer? C Language III. CMSC 313 Sections 01, 02. pointer = memory address + type

Pointer Basics What is a pointer? pointer = memory address + type C Language III CMSC 313 Sections 01, 02 A pointer can contain the memory address of any variable type A primitive (int, char, float) An

### Pointers in C/C++ 1 Memory Addresses 2

Pointers in C/C++ Contents 1 Memory Addresses 2 2 Pointers and Indirection 3 2.1 The & and * Operators.............................................. 4 2.2 A Comment on Types - Muy Importante!...................................

### 10/20/2015. Midterm Topic Review. Pointer Basics. C Language III. CMSC 313 Sections 01, 02. Adapted from Richard Chang, CMSC 313 Spring 2013

Midterm Topic Review Pointer Basics C Language III CMSC 313 Sections 01, 02 1 What is a pointer? Why Pointers? Pointer Caution pointer = memory address + type A pointer can contain the memory address of

### THE GOOD, BAD AND UGLY ABOUT POINTERS. Problem Solving with Computers-I

THE GOOD, BAD AND UGLY ABOUT POINTERS Problem Solving with Computers-I The good: Pointers pass data around efficiently Pointers and arrays 100 104 108 112 116 ar 20 30 50 80 90 ar is like a pointer to

### Character Strings. String-copy Example

Character Strings No operations for string as a unit A string is just an array of char terminated by the null character \0 The null character makes it easy for programs to detect the end char s[] = "0123456789";

### Dynamic Data Structures. CSCI 112: Programming in C

Dynamic Data Structures CSCI 112: Programming in C 1 It s all about flexibility In the programs we ve made so far, the compiler knows at compile time exactly how much memory to allocate for each variable

### Processor. Lecture #2 Number Rep & Intro to C classic components of all computers Control Datapath Memory Input Output }

CS61C L2 Number Representation & Introduction to C (1) insteecsberkeleyedu/~cs61c CS61C : Machine Structures Lecture #2 Number Rep & Intro to C 2005-08-31 There is one handout today at the front and back

### Contents of Lecture 3

Contents of Lecture 3 Repetition of matrices double a[3][4]; double* b; double** c; Terminology Linkage Types Conversions Jonas Skeppstedt (js@cs.lth.se) Lecture 3 2014 1 / 33 A global matrix: double a[3][4]

### Understanding Pointers

Division of Mathematics and Computer Science Maryville College Pointers and Addresses Memory is organized into a big array. Every data item occupies one or more cells. A pointer stores an address. A pointer

### CS113: Lecture 5. Topics: Pointers. Pointers and Activation Records

CS113: Lecture 5 Topics: Pointers Pointers and Activation Records 1 From Last Time: A Useless Function #include void get_age( int age ); int age; get_age( age ); printf( "Your age is: %d\n",

### CS61C : Machine Structures

inst.eecs.berkeley.edu/~cs61c CS61C : Machine Structures Lecture #2 Number Rep & Intro to C 2005-08-31 There is one handout today at the front and back of the room! Lecturer PSOE, new dad Dan Garcia www.cs.berkeley.edu/~ddgarcia

### Chapter 2 (Dynamic variable (i.e. pointer), Static variable)

Chapter 2 (Dynamic variable (i.e. pointer), Static variable) August_04 A2. Identify and explain the error in the program below. [4] #include int *pptr; void fun1() { int num; num=25; pptr= &num;

### CSC C69: OPERATING SYSTEMS

CSC C69: OPERATING SYSTEMS Tutorial 1 Thursday, Jan 17, 2013 TA: Ioan Stefanovici (ioan@cs.toronto.edu) HOW DO YOU SUCCEED IN THIS COURSE? Show up to lectures & tutorials (way too much material) Work on

### CSCI-1200 Data Structures Spring 2017 Lecture 5 Pointers, Arrays, Pointer Arithmetic

CSCI-1200 Data Structures Spring 2017 Lecture 5 Pointers, Arrays, Pointer Arithmetic Announcements Submitty iclicker registration is still open. Even if you already registered on the iclicker website,

### Incoming Exam. CS 201 Introduction to Pointers. What is a Pointer? Pointers and Addresses. High Speed Memory (RAM) Size of Variable Types.

Incoming Exam CS 0 Introduction to Pointers Debzani Deb Next Monday (th March), we will have Exam # Closed book Sit with an empty space in either side of you Calculators that have text-allowing is not

### CS2351 Data Structures. Lecture 7: A Brief Review of Pointers in C

CS2351 Data Structures Lecture 7: A Brief Review of Pointers in C 1 About this lecture Pointer is a useful object that allows us to access different places in our memory We will review the basic use of

### Introduction to C. Robert Escriva. Cornell CS 4411, August 30, Geared toward programmers

Introduction to C Geared toward programmers Robert Escriva Slide heritage: Alin Dobra Niranjan Nagarajan Owen Arden Cornell CS 4411, August 30, 2010 1 Why C? 2 A Quick Example 3 Programmer s Responsibilities

### Memory Corruption 101 From Primitives to Exploit

Memory Corruption 101 From Primitives to Exploit Created by Nick Walker @ MWR Infosecurity / @tel0seh What is it? A result of Undefined Behaviour Undefined Behaviour A result of executing computer code

### CS 222: Pointers and Manual Memory Management

CS 222: Pointers and Manual Memory Management Chris Kauffman Week 4-1 Logistics Reading Ch 8 (pointers) Review 6-7 as well Exam 1 Back Today Get it in class or during office hours later HW 3 due tonight

### Introduction to C. Sean Ogden. Cornell CS 4411, August 30, Geared toward programmers

Introduction to C Geared toward programmers Sean Ogden Slide heritage: Alin Dobra Niranjan Nagarajan Owen Arden Robert Escriva Zhiyuan Teo Ayush Dubey Cornell CS 4411, August 30, 2013 Administrative Information

### Hacking in C. Pointers. Radboud University, Nijmegen, The Netherlands. Spring 2019

Hacking in C Pointers Radboud University, Nijmegen, The Netherlands Spring 2019 Allocation of multiple variables Consider the program main(){ char x; int i; short s; char y;... } What will the layout of

### Introduction to C. Ayush Dubey. Cornell CS 4411, August 31, Geared toward programmers

Introduction to C Geared toward programmers Ayush Dubey Slide heritage: Alin Dobra Niranjan Nagarajan Owen Arden Robert Escriva Zhiyuan Teo Cornell CS 4411, August 31, 2012 Administrative Information Outline

### Last week. Data on the stack is allocated automatically when we do a function call, and removed when we return

Last week Data can be allocated on the stack or on the heap (aka dynamic memory) Data on the stack is allocated automatically when we do a function call, and removed when we return f() {... int table[len];...