Extra_class_with_notes.pptx

7/27/2019 Extra_class_with_notes.pptx

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CS1010: Programming Methodologyhttp://www.comp.nus.edu.sg/~cs1010/
http://www.comp.nus.edu.sg/~cs1101/http://www.comp.nus.edu.sg/~cs1101/


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Extra class: 21 September 2011

Objectives:

To go over the basic concepts covered in the first

6 weeks

To give out some programming exercises to teststudents understanding of these basic concepts

CS1010 (AY2011/2 Semester 1) Extra Class - 2


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Summary (1/2)

Week 2: Writing algorithms (pseudo-codes)

Input (scanf) and output (printf)

Types (int, float, double, char, etc.) and variables

Mathematical operations (*, /, %, +, -)

About integer division

Week 3:

Top-down design

Writing functions: The NOT acronym

Using math functions

Discussion: Writing algorithms, programming environment.



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Summary (2/2)

Week 4: Selection statements: if, if-else, switch

Discussion: inaccuracy of real numbers, initialisation of variables,redundant assignment, using selection statements, conditional

operator ?:, writing functions.

Week 5: Repetition statements: while, do-while, for

Week 6:

Functions with address parameters

Modular programming and separate compilation

Discussion: tracing of loops, writing loops, functions with addressparameters, design issues, exploration on random numbers.



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Skills

Using vim

Pseudo-code before code Clear logic

Can you convince yourself that your algorithm works before you

start typing the program?

Simplifying the problem If you get a complex problem, what would you do? (Reference:

Week 6 Discussion Q5 Asterisks)

Incremental coding Do you type in the whole program at one go? Or a bit at a time?

Understanding compilers messages Do you know where to zoom into your program to spot the error?



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Week 6 Discussion Q5: Asterisks

(b)


*

***

*****

*

***

*****

*******

*********

***********

(c)

*

***

*****

*

***

************

*********

***********


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Big Question

Have you been writing a lot of programs by yourself? Target: Write 100 programs by the

end of this semester

For students with no experience: 150programs

Possible!Average about 15 programs per week, or 2

programs per day.



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Tracing

Another important skill: Tracing codes. Reinforce that program execution is done step by step

following the sequence, selection and repetition control

structures.

Every variable should be represented by a box, and its value

updated during the trace.

Manually trace the given programs in the hand-out,

and write out their outputs.



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Count multiples of 5 or 7

Write a program multiples5or7.c that asks user for apositive numbernum, and count the number of

multiples of 5 or 7 in the range [1, num].

Time limit: 10-15 minutes

Sample runs:


Enter positive integer: 10

There are 3 multiples of 5 or 7 in [1,10].


There is 1 multiple of 5 or 7 in [1,6].


There are 16 multiples of 5 or 7 in [1,50].


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Perfect numbers (1/2)

Definition: A perfect numberis a positive integer that is the sum of its

proper positive divisors.

Examples:

6 is a perfect number, because 6 = 1 + 2 + 3

8 is not a perfect number, because 8 1 + 2 + 4

100 is not a perfect number, because 100 1 + 2 + 4 + 5 +

10 + 20 + 25 + 50

Write a program check_perfect.c that asks user

repeatedly for a non-negative integer, and stops whenthe number is zero.

For each positive integer entered, your program is to

check whether it is a perfect number or not.



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Perfect numbers (2/2)

Time limit: 20-25 minutes Sample run:


Enter number: 6

6 is a perfect number.

Enter number: 88 is a not perfect number.

Enter number: 100

100 is not a perfect number.

Enter number: 0


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Check order of input data (1/2)

Write a program check_order.c to read in a list ofpositive integers.

The program is to continue asking for the next

positive integer as long as the integers entered so far

are in increasing order. The moment the input data are not in increasing

order, or the input value is zero, the input ends.

The program should then report whether the input

data are in increasing order or not. You may assume that at least one positive integer is

entered. If that is the case, we treat the list as in

increasing order.



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Check order of input data (2/2)

Time limit:20-25

minutes

Sample

runs:


Enter positive integer:3


Data are in increasing order.




Enter positive integer: 0Data are in increasing order.




Data are not in increasing order.





Data are not in increasing order.


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Reminders

Revise all of the following Textbook and lecture notes

Discussion questions

Lab exercises

Write many programs! Post queries on IVLE forum and read

postings by others

You CAN succeed!



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End of File


Extra_class_with_notes.pptx

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