• People and Website
• Course Goals
• Course Context
• Revision (material from COMP1511)
• Data Structure Viewpoint
• COMP2521 Themes
• Lectures
• Tutes and Labs
• Assignments
• Plagiarism
• Final Exam
• Supplementary Exams
• Course Assessment
• C vs COMP1511 vs COMP2521
• Switch-statements
• For-loops

♢ Lecturer-in-charge: Dr Ashesh Mahidadia ♦ Email: ashesh@cse.unsw.edu.au

♢ Course Admin Email: cs2521@unsw.edu.au

♢ Primary entry point is WebCMS,
        Course Website is:   https://webcms3.cse.unsw.edu.au/COMP2521/20T1/

♢ Login to WebCMS using your zID and your zPass, and is needed for

• course material (lecture slides, tutorials, labs, assignments, etc.)
• polls
• comments/forums
• forming groups
• etc. ...

COMP1511 ...

• gets you thinking like a programmer
• solving problems by developing programs
• expressing your ideas in the C language

• gets you thinking like a computer scientist
• knowing fundamental techniques/structures
• able to reason about applicability/effectiveness
• able to analyse behaviour/correctness of programs

COMP1511 ...

COMP2521 ...
 

♢ At the start of this course you should be able to:

• produce a correct C program from a specification
• understand the state-based model of computation
  (variables, assignment, addresses, parameters, scope)
• use fundamental C data structures
  (char, int, float, arrays, structs, pointers, linked lists)
• use fundamental control structures   (if, while)
• implement abstraction via function declarations, ADTs
• fix simple bugs in incorrect programs

♢ Important: Make sure you can properly understand and effectively use the following topics (covered in COMP1511):

• Structs (see videos on Structs, click here)
• Pointers (see videos on Pointers, click here)
• Malloc (see videos on Malloc, click here)
• Linked Lists (see videos on Linked Lists, click here)

♢ At the end of this course you should be able to:

• analyse performance characteristics of algorithms
• measure performance behaviour of programs
• choose/develop effective data structures (DS)
• choose/develop algorithms (A) on these DS
• package a set of DS+A as an abstract data type
• develop and maintain 9999-line C programs

COMP1511 considered ...

COMP2521 also considers ...

♢ Major themes ...

1. Analysis: correctness, performance, usability
2. ADTs: sets, lists, trees, graphs, dictionaries
3. Operations: building, sorting, searching, traversing

♢ For data types: alternative implementation of operations

♢ For algorithms: complexity analysis, performance analysis

♢ Always give credit if you use someone else's work.

♢ COMP2521 material is prepared by John Shepherd, and ideas are drawn from

• notes by Aleks Ignjatovic (COMP2011 2005)
• slides by Manuel Chakravarty (COMP1927 08s1)
• lectures by Richard Buckland (COMP1927 09s2)
• slides by Gabrielle Keller (COMP1927 12s2)
• slides by Michael Thielscher (COMP9024 17s2)
• slides and books by Robert Sedgewick

♢ Textbook is a "double-header"

• Algorithms in C, Parts 1-4, Robert Sedgewick
• Algorithms in C, Part 5, Robert Sedgewick

       

Good books, useful beyond COMP2521, but code style .....

♢ Four scheduled hours of lectures.

♢ Lectures will contain ...

• summary of content   (read textbook and lecture notes in advance),
• problem-solving exercises, hopefully, with lots of input from you.

♢ But without any "background noise" :-)

♢ Tutorials ...

• as in COMP1511
• analysis/design practice; clarify lecture material

♢ Labs ...

• small(ish) implementation tasks, done in pairs
• give skills practice (leading on to assignments/exam)

♢ Tutes/labs will run from week 01 to 10.

♢ Exercises for Week X available in Week X-1

♢ Lab exercises contribute 11% to overall mark.

♢ The lab exercises for Week X must be

• submitted before Sunday at end of week X
• demonstrated to tutor during Week X lab
  OR, demonstrated at the start of Week X+1 lab

♢ Total mark for all the labs is greater than 11 (and they are scaled to 11).

♢ Two assignments ...

• Ass1:   15% towards final mark,   (available in week-03, due Mon week-07)
• Ass2:   20% towards final mark,   (available in week-07, due in week-10)

♢ Two assignments contribute 35% towards final mark.

♢ Late penalties apply if you miss the deadline.

♢ Good time management avoids late penalties!

♢ 3-hour on-line exam during the exam period.

♢ How to pass?   Practice, practice, practice, ...

♢ The document "Essential Advice for CSE Students" states the supplementary assessment policy for the School of CSE. Please take the time to read it carefully.

♢ If you are granted a Supplementary examination, then it will be centrally timetabled. If you think that you may be eligible for a supplementary exam, then make sure you are available on that day. It is your responsibility to check at the Student Office for details of Supplementary examinations.

quizzes             = mark for quizzes               (out of  14)
labs                = mark for lab exercises         (out of  11)
ass1                = mark for assignment 1          (out of  15)
ass2                = mark for assignment 2          (out of  20)
finalExam           = mark for final exam            (out of  40)

okHurdle            = finalExam > 20 (that is, > 50% in the final exam)

mark      = quizzes + labs + ass1 + ass2 + finalExam
grade     = HD|DN|CR|PS  if mark >= 50 && okHurdle
          = FL           if mark <  50
          = UF           if mark >= 50 && !okHurdle

♢ The goal is for you to become a better programmer

• more confident in your own ability
• with an expanded set of tools to draw on
• able to analyse/justify your choices
• producing a better end-product
• ultimately, enjoying the programming process

♢ Required use of a restricted subset of C:

• layout, use of brackets (always)
• use only if and while
• no side-effects in expressions
• no conditional expressions
• all functions have one return statement

♢ But ... this style used in no texts or real code.

♢ Extends the range of allowed constructs:

• layout: consistent indentation still required
• use of brackets:
  • can omit if control structure owns a single statement
  • put function start bracket on line after function header
• can use all C control structures
  • if, switch, while, for, break, continue
  • put function start bracket on line after function header

♢ But wait! There's more ...

♢ More allowed C constructs ...

• can use assignment statements in expressions
  • but you should continue to avoid other kinds of side-effects
• can use conditional expressions
  • but use   x = c ? e1 : e2   with care
• functions may have multiple return statements
  • use very sparingly, primarily for error handling

♢ Good: gives you more freedom and power

• more choice in how you express programs
• can write code which is more concise (simpler)

♢ Bad: gives you more freedom and power

• can write code which is more cryptic
• can lead to incomprehensible, unmaintainable code

♢ So, you must still use some discipline.

♢ switch encapsulates a common selection:

if (v == C1) {
   S1;
} else if (v == C2) {
   S2;
}
...
else if (v == Cn) {
   Sn;
}
else {
   Sn+1;
}

♢ Multi-way if becomes:

switch (v) {
case C1:
   S1; break;
case C2:
   S2; break;
...
case Cn:
   Sn; break;
default:
   Sn+1;
}

♢ Note: break is critical; if not present, falls through to next case.

♢ Write a function monthName(int) that

• accepts a month number 1=Jan ... 12=Dec
• returns a string containing the month name
• assume that the string will be read-only
• use a switch to decide on the month

♢ Suggest an alternative approach using an array.

♢ for encapsulates a common loop pattern:

init;
while (cont) {
   do something;
   incr;
}

as

for (init; cont; incr)
   do something;

♢ COMP1511 (while) version

sum = 0;
i = 1;
while (i < 10) {
    sum = sum + i;
    i++;
}

♢ COMP2521 (for) version

sum = 0;
for (i = 0; i < 10; i++)
    sum += i;

Write a program that prints integer sequences (one per line):

• seqq 10   prints   1 2 3 4 5 6 7 8 9 10
• seqq 5 10   prints   5 6 7 8 9 10
• seqq 10 1   prints   10 9 8 7 6 5 4 3 2 1
• seqq 1 3 10   prints   1 4 7 10
• seqq 1 3 11   prints   1 4 7 10
• seqq -3   prints   1 0 -1 -2 -3
• seqq 1 -3 10   gives an error

♢ Package the core part as a function:

void seq(int start, int step, int finish) {...}

main checks errors and sets up args for seq()