CSCI 2132Software Development

Lecture 35:

Dynamically Allocated Arrays, Course Review

Instructor: Vlado Keselj

Faculty of Computer Science

Dalhousie University

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Previous Lecture

• Shell Scripting (continued)• conditional expressions on files• exit code, example• Dynamic Arrays

– String examples– Example reversewords

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Reversing the Words, Revisited

• Another idea:– Reverse the complete string– Reverse each word within string once more

• Fill-in-the-blanks code available in

˜prof2132/public/reversewords2.c-blanks

(in one line)

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Dynamically Allocated Arrays

• Similarly to strings we can allocate arbitrary arrays; for example:

int *array, i;array = (int*) malloc(n * sizeof(int));if (array == NULL) {...

}for (i = 0; i < n; i++)array[i] = 0;

...free(array);

• or simpler

int *array;array = (int*) calloc(n, sizeof(int));if (array == NULL) { ... /* error */ }

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Dynamically Allocated Arrays andVLAs

• Using dynamic memory vs VLA• VLAs are allocated and deallocated more

efficiently (on stack)• Heap more appropriate for large arrays• Heap appropriate for arbitrary lifespan• Heap more appropriate for portability (C99)

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Mergesort Using Dynamic Arrays

• Fill-in-the-blanks code available at:

˜prof2132/public/mergesort3.c-blanks

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Dynamic Arrays: Resizable Arrays

• How to implement something like ArrayList in Java, or vector class inC++?

• Pseudocode for adding elements:

If array is fullResize the array to twice its current capacity

using reallocStore the new element

• The main structure:

struct vector {int *array;int capacity;int size;

}

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Resizable Array Implementation:dynamicarray.c-blanks

• Fill-in-the-blanks implementation can be foundat:

˜prof2132/public/dynamicarray.c-blanks

(one line)

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Dynamic Array: Time Complexity

• What can happend when push_back is calledregarding execution time?

• Why do we consider this a reasonably efficientsolution?

• Why we must be careful when determiningwhen to shrink the array?

• This provides a better explanation of behaviourof the ArrayList in Java and the vector class inC++

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Final Exam Studying

• Lecture notes and Lab notes• Textbook reading (according to the list)• Assignments and exams (midterms and

samples)• Textbook questions• Textbook exercises

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Course Review

• Lecture 1: Course Introduction– Course Introduction∗ logistics and administrivia∗ important dates, course description∗ evaluation scheme and criteria∗ textbooks∗ lectures, exams, assignments, lab work

– Academic integrity policy– Culture of respect– Main learning objectives

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• Part I: Unix Operating System• Lecture 2: Introduction to UNIX and Unix-like Operating

Systems– Motivation: Why UNIX, Why C– Tentative list of course topics– Introduction to UNIX– Reading: Chapter 1 of the UNIX book– Onion skin model of OS– OS functionalities– UNIX history

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• Lecture 3: Files and Directories– Main UNIX concepts– Unix architecture– Shells– Logging in– PuTTY– Some basic utilities and commands∗ date, clear, passwd, man

– Shell metacharacters– ‘cat’ example, file redirection– Logging out– Files and Directories

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• Lecture 4: File Permissions– Pathnames– Commands for managing and navigating directory

structure– Commands: cat, logout, exit, ls, dirname, basename,

pwd, cd, mkdir, rmdir, mv, rm, tree– File manipulation, commands– File permissions:∗ users, groups∗ checking permissions

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• Lecture 5: File Permissions, I/O Redirection– Changing file permissions– Changing user and group owners– Redirection∗ standard input, output, and error

• Lecture 6: Links and Inodes– Pipes– Inodes– Hard links– Soft links

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• Lecture 7: Wildcards and Regular Expressions– Filename substitution (wildcards)– Regular expressions∗ basic regular expressions∗ grep, filters

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• Lecture 8: Shells, Processes, and Job Control– Extended regular expressions (ERE)– Shells and Job Control– Shells∗ functionality∗ popular shells

– Bash shell∗ commands∗ variables

– Processes and programs∗ process memory composition

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• Part II: C programming Language and SoftwareDevelopment

• Lecture 9: Job Control, Introduction to C– Processes and programs∗ process memory composition∗ threads∗ process Control Block (PCB)

– Process creation∗ fork and exec system calls

– Job control and process control∗ foreground and background processes∗ commands for managing jobs and processes

– Introduction to C

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• Lecture 10: Formatted Input and Output– Introduction to C: writing a simple program– Compilation process– C Language Basics:∗ program structure, preprocessor directives, functions∗ statements∗ string literals and printing strings

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• Lecture 11: Formatted Input and Output– C Language Basics (continued):∗ input and output∗ constants∗ simple example

– Formatted input and output∗ printf∗ scanf

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• Lecture 12: Examples with scanf– Conversion specifications for scanf, examples– Operators, expressions: Java vs. C

• Lecture 13: Expression and Control Structures– C control structures; comparison with Java– Implementation-defined and unspecified behaviour– Logic expressions– Differences between C99 and earlier standards– goto statement, null statement

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• Lecture 14: Software Development Life Cycle– Software Development Life Cycle (SDLC)– Waterfall model– Rapid prototyping model– Software testing

• Lecture 15: C Basic Types– Software testing and debugging, gdb– C basic types– Integer types– Integer type specifiers– Integer representation– Floating-point number types

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• Lecture 16: C Arrays– Character types– Type conversion– Implicit type conversion of operands and assignments– Explicit type conversion (type casting)– typedef and sizeof keywords– C Arrays: one-dimensional arrays

• Lecture 17: Array Example, Multidimensional Arrays– Example: binary search– Multidimensional arrays– Variable-length arrays

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• Lecture 18: Functions– Example: Latin square– Function definitions– Function declarations or prototypes– Arguments and parameters– Arguments passed by value– Call stack– Simple recursion example: power

• Lecture 19: Recursion Examples: Mergesort– Mergesort implementation and discussion

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• Lecture 20: Recursion Examples: Quicksort andPermutations– Mergesort complexity calculation– Quicksort vs Mergesort– Example: Generating permutations

• Part III: Program Organization and Dynamic MemoryAllocation

• Lecture 21: Program Organization– Generating permutations (finished)– Multidimensional arrays as arguments– Program Organization:– Local variables– External (global) variables

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• Lecture 22: Pointers– Organizing a C program in a single file– Example: Decimal to binary– Blocks and compound statements; Scope– Pointers: Reading: Ch12 Pointers– Introduction and history– Pointer variables, reference type– Address operator (&), indirection operator (*)– Pointer Assignment– Pointer Examples

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• Lecture 23: Pointers and Arrays– Pointer assignment– Pointer arguments– Example: statistics.c– Pointers and arrays– Pointer arithmetic: pointer + integer

• Lecture 24: Pointer Examples– Pointer arithmetic: subtraction and comparison– Pointer examples– Mergesort revisited, with pointers

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• Lecture 25: Strings– Midterm 2 review– Finished mergesort2 “fill-in the blanks”– Strings:– String literals– String variables

• Lecture 26: String Library– Assignment discussion– Reading and writing strings– String library functions

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• Lecture 27: Writing Large Programs– String library functions (continued)– Command-line arguments– sortwords.c example with insertion sort– Writing large programs: header files and “.c” files– modules and header files

• Lecture 28: Compilation of Large Programs– Protecting header files from double-inclusion– prj-dec2bin and stack example– Compilation of large programs– make utility (started)

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• Lecture 29: Dynamic Memory Allocation– make utility– Using gdb with multi-file programs– Structures– Arrow operator– Dynamic memory allocation: malloc and free

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• Lecture 30: Linked Lists– Linked lists– Linked list example: student database– Analysis of the program list.c

• Lecture 31: Mergesort with Linked Lists– Mergesort with linked lists∗ Algorithm∗ Example with students database: sortlist.c

• Lecture 32: File Operations in C– Heap (Free Store)– File Manipulation in C:– Opening a file, closing a file– Formatted I/O, character I/O

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• Lecture 33: Shell Scripting– Block reading and writing– File positioning– Examples– Shell Scripting: introduction, a basic example– variables– arithmetic operations, conditional expressions– ‘if’ statement, ‘for’ loop– ‘case’ statement

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• Lecture 34: Dynamically Allocated Arrays– Shell Scripting (continued)– conditional expressions on files– exit code, example– Dynamic Arrays∗ String examples∗ Example reversewords

• Lecture 35: Dynamically Allocated Arrays, CourseReview

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• Lab 1: UNIX: Getting Started– Logging into server: putty, ssh– pwd– mkdir, ls, chmod– lab1 directory– Preparing Java file in Emacs– Compiling and running Java program– Using emacs for search-and-replace– Using submit command– Command head

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• Lab 2: Unix Utilities; Emacs– Autocompletion in Bash– Emacs: beginning and end of a line– Emacs: copy and paste, cut and paste– Emacs: undo– Filters: uniq, sort, sort with CSV– cut, a pipe example

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• Lab 3: SVN Source Version Control Tutorial– Learning about SVN Source Version Control system– Concept of repository and working copy– Checkout and Adding a Directory– Commit Command– Adding Files– Deleting Files– Checking out second copy– Changing files, update– Accidental Delete– Parallel Changes, merging changes, conflicting

changes

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– Retrieving copies of previous work

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• Lab 4: Exploring bash and C Compilation– echo, /etc/shells, .bashrc, .profile– diff– Writing a C program, compiling, using Emacs to

compile– Suspending Emacs– Examining exit code: $?– Email client: pine

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• Lab 5: Dr. Tig’s Git Tutorial– What is Git? What is GitHub?– Cloning– History, git log– Branches– Diff, Branch Diff– Creating a repository– git config, editor– Commit– Merge and merge conflicts– Optional sharing

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• Lab 6: Formatted Input and Output– man command, reading about printf and scanf– Experiments with printf– C Compilation in Emacs, setting hot keys– Multiple windows in Emacs– Precision in printf, exploring scanf– An exercise: phone numbers

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• Lab 7: gcc and gdb– gcc options: -Wall, -g– gdb: running, breakpoints– Using gdb in emacs– gcc option -std

– Debugging an incorrect program:– Compiling binary.c (binary search)– Running gdb to find a bug– Finding another bug: setting break points, print, display– Testing program

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• Lab 8: Practicum 1• Lab 9: Practicum 2• Lab 10: Practicum 3

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• Lab 11: Make Utility– Getting a copy of directory lab-make– Running make commands– Using make variables– Preparing make for gdb– Dividing a program into multiple files

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• Lab 12: Shell Scripting• Starting with Shell Scripting• Simple “Add” Script• Using For Loop• For Loop, another form• Using the Case Statement• “Save” Example

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