cs1032 2013batch lecture 1

CS1032

Programming Fundamentals

Prof. Sanath Jayasena Dept. of Computer Science & Engineering

Semester 1 (2013 Batch)

[Mar - July, 2014]

1. Course Description

2. Lecture Session 1

1. Course Description

CS1032

Programming Fundamentals

(3 credits)

Can be found in:

• the Course Outline document (copies given)

• the course LMS site at http://online2.mrt.ac.lk/course/view.php?id=2

http://online2.mrt.ac.lk/course/view.php?id=2


Learning Outcomes

• After completing this course, the students

will be able to:

– Device algorithms to solve simple engineering

and computational problems

– Develop programs from algorithms using a

programming language such as Python

– Use an Integrated Development Environment

(IDE) for program development

3 Sanath Jayasena, March 2014

Main Staff

• Coordinator: Prof. Sanath Jayasena

• Staff for lecture sessions

– Prof. Sanath Jayasena, Dr. Chathura De

Silva, Dr. Shehan Perera, Dr. Malaka Walpola

• Labs coordinated by:

– Mr. Adeesha Wijayasiri

• Other staff (e.g., Instructor in-charge)

– Get to know in the lab


Course Material

• Course on the LMS

– http://online2.mrt.ac.lk/course/view.php?id=2

– Contain all resources and activities

• Two documents will be distributed

– Course Notes for CS1032 (first, Part A)

– Lab Exercises for CS1032

– Have them with you in lectures, lab sessions

– Remainder will be given later




Additional Reading

• Learning Python, 5th Edition by Mark Lutz, O'Reilly Media, 2013

• Introduction to Computing Using Python:

An Application Development Focus, by

Ljubomir Perkovic, Wiley, 2012

• Python Tutorials and Documentation

– http://www.tutorialspoint.com/

– http://docs.python.org/2/tutorial/

– http://docs.python.org/2/contents.html


Method of Assessment

• Credits:3

• Final written examination: 80%

– 3 hours; mix of MCQ, short and structured Qs

• Continuous Assessments (CA): 20%

– 5 Evaluated Labs, 1% each 5%

– Programming Assignment 1 7.5%

– Programming Assignment 2 7.5%


Assessment of Programs

1. Problem not attempted to satisfactory level 0% - 25%

2. Problem attempted, code has syntax errors30% max

3. Problem attempted, no syntax errors 50% max

4. (3) Above + code runs without crashing or unexpected

termination + some results/output may not be correct

70% max

5. (3) Above + code runs without crashing or unexpected

termination + results/output are correct 90% max

6. Programming style (comments, variable naming…)

10% max


Rules, Regulations

• 35% each from CA and Exam required to

pass the course module

• Must comply with rules of UoM

– Serious consequences if violated

• E.g., copying, letting copy, plagiarism, conduct

during exams and CA work, sharing of computer

passwords, unauthorized access

• Missed lab (CA) session?

– Another chance may be given based on

• Reason, evidence, how soon informed


Course Schedule

• Lecture sessions:

– 2 hours per week

• Group A: Wed 08.15am-10.15am, Aud-1

• Group B: Fri 10.15am – 12.15pm, Aud-2

• Group C: Mon 08.15am-10.15am, Aud-2

• Venues: Auditoriums 1, 2


Course Schedule

• Labs: 3 hours per week (CSE Level 1 Lab, CITeS Lab)


Group A-1 Tuesday 08.15-11.15am

Group A-2 Friday 12.15-03.15pm

Group A-3 Thursday 01.15-04.15pm

Group A-4 (ER) Wednesday 03.15-06.15pm

Group B-1 Thursday 08.15-11.15am

Group B-2 Wednesday 12.15-03.15pm

Group B-3 Monday 03.15-06.15pm

Group B-4 (TL) Monday 12.15-03.15pm

Group B-5 Monday 08.15-11.15am

Group C-1 Friday 03.15-06.15pm

Group C-2 Wednesday 08.15-11.15am

Group C-3 Friday 08.15-11.15am

Group C-4 (TX) Tuesday 01.15-04.15pm

Course Outline (Lectures)

– Overview of programming

• Algorithms and problem solving

• Introduction to C

– Programming in Python

• Data types, expressions, data representation

• Control structures: selection, loops, functions

• Lists, input, output and file handling

– Computer system hardware

– Beyond basics: Introduction to

• Problem solving, algorithms, data structures,

software engineering


Course Outline (Labs)

• Lab 1, 2: Introduction to Python Programming

• Lab 3: Conditional (Selection) Structures

• Lab 4: IDEs and Debuggers

• Lab 5: Loop Control Structures (E)

• Lab 6: Lists (E)

• Prog. Assign-1 (7.5%)

• Lab 7: Functions (E)

• Lab 8: File Handling (E)

• Lab 9: File Handling & Functions (E)

• Lab 10:

• Prog. Assign-2 (7.5%)

See the Course

Schedule or the

LMS for detailed

schedule


On Labs, CA Work…

• Be punctual

• Follow the “Lab Rules”

• Ask for clarifications if you need any

• Deadlines must be met

• Don’t cheat

• Follow the instructions given for lab

sessions (you have to READ!)

• Give us feedback Any questions?


2. Lecture Session 1

Background,

Overview of “C”,

Introduction to Python

Outline

• Background

– Programs

– Program development

• Program translation

– Compilation vs Interpretation

• Overview of the “C” language

• Introduction to Python


Background

• Program

– an ordered sequence of instructions that the

hardware can execute

– tells a computer (how) to perform a task

• A computer program is expressed using a

programming language

• Computer programming

– The art of developing computer programs

– Core part of software development


Introduction

• Programmers develop programs,…by

– developing an algorithm to solve the problem

(to complete the given computational task)

– converting the algorithm into a program

– testing the program to see whether it works as

expected and taking corrective actions if not

• Algorithm

– a sequence of a finite number of well-defined

steps for solving a problem


Program Development

1. Define the problem

2. Outline the solution

3. Develop an algorithm

4. Test the algorithm for correctness

5. Code the algorithm in a suitable language

6. Ensure program has no syntax errors

7. Compile to generate translated code (optional)

8. Run the program

9. Test and debug the program

10.Document and maintain the program

As needed


Developing an Algorithm

• Algorithm should consist of a precise, clear and

finite sequence of steps to solve the problem

• More than one algorithm could exist for a given

problem

• Developing an algorithm is the most important

step in the process of developing a program

• For a complex problem, developing an algorithm

is generally the most difficult part


Expressing an Algorithm

• Pseudocode (a structured form of the

English language) can be used

• Example

Step 1. Start

2. Input r

3. Compute circumference: c 2 * PI * r

4. Compute area: a PI * r * r

5. Output c and a

6. Stop

• ‘PI’ is the value of π; ‘*’ is the multiplication operator 21 Sanath Jayasena, March 2014

Expressing an Algorithm

• Flowcharts can also be used

Symbol Description

Flow is used to connect different symbols and

indicates the direction of flow of the algorithm.

Process symbol can be used for a single step or an

entire sub process.

Decision indicates a choice and selection of a path

by the algorithm based on a certain criteria.

Input / Output represents input or output data to the

algorithm.

Start / Stop represents the start / end of the

algorithm.


Example 1

Start

Stop

Output c and a

c 2 * PI* r

a PI * r * r

Input radius r


Example 2

(a) Pseudo code

1. Start

2. Num 1

Total 0

3. Total Total + Num

Num Num + 1

4. If Num ≤ 100 go to Step 3

{ implied: else go to Step 5 }

5. Output Total

6. Stop

Start

Stop

Output Total

Num 1

Total 0

Num ≤

100?

Total Total + Num

Num Num + 1

Yes

No

(b) Flowchart Compute the sum of numbers 1-100


Program Translation

• Programs developed in human-readable

high-level languages (source code)

• Computer understands 1’s and 0’s

– the machine language or machine code

• Program translation options:

– Compilation by a compiler

– Interpretation by an interpreter

– […depending on whether we have a

compiled-implementation or an interpreted-

implementation for the source language] 25 Sanath Jayasena, March 2014

Compilers & Compilation


Compilation (Translation)

Source

Program Executable

Machine Code Compiler

Execution

Input Output Executable

Machine Code

Compilation

• Compilation: source code program machine-

code (object code) program

• Linking: object code with other object code

executable machine-code program

• Machine code can be saved on disk (as object

files or executable file) and reused

• No recompilation unless the source changed

• Example compiled-implementations:

– FORTRAN, COBOL, C, C++, Java and Pascal


Translation and Execution

Interpreters & Interpretation

Source

Program

Interpreter

Input

Output


Interpretation

• For each source code statement

– First, translate into machine-code

– Next, execute the machine code

• Translation done for every execution

– Machine-code of the full original source

program is neither produced nor saved

– Execution slower than compiled code

• Example interpreted-implementations

– BASIC, Perl, Python, Ruby,…

Sanath Jayasena, March 2014 29

• Syntax errors: violation of syntax

(grammar) rules of the source language

– Compiler/interpreter will complain; fix by

editing the source program

• A syntactically correct program may still

have bugs (other errors or faults)

– While the program is running runtime errors

may cause unexpected termination

– Program not doing what it is supposed to do

due to logic errors

Errors in Programs


Overview of “C”

• “C” : one of the most widely used languages

– Stable, portable, standardized

• Various languages have branched away

from C; e.g., C++, Java, C#

• C programmers have power and flexibility to

make programs fast and efficient

– Comes at a cost: strongly-typed, strict syntax,

burden of managing memory,…


Creating a C program

• A programmer uses a text editor program

to create/modify C source (code) files

– C source files are given the extension “.c”

• Then the programmer must invoke the C

compiler to compile it

– Depending on the “development

environment”, compilation methods may differ

– E.g., command-line or graphical interfaces


• To compile using the gcc compiler at the command-line (shell) prompt, type $ gcc SourceFileName.c

• If there are no errors, this will produce an executable file named a.out

• To execute the program type at the command-line prompt

$ ./a.out

Compiling and Running

a C Program on Linux


Three Stages of Translation

• The translation of a C program in reality

consists of 3 stages (one of them is

compiling)

1. Preprocessing

2. Compiling

3. Linking


1-35 Sanath Jayasena, March 2014

1. Preprocessing

• Performed by a program called the preprocessor

• Modifies the source code (in memory) according

to preprocessor directives embedded in source

– E.g., #define, #include, #ifdef

– Strips comments and white space from the code

• The source code stored on disk is not modified

• May issue error messages and stop without

success if problems encountered


2. Compiling

• Performed by the compiler

• Translates the preprocessor-modified source code into object code (machine code), which is not “executable” as yet

• Checks for syntax errors and violation of other language rules

– May issue warnings and still proceed

– May terminate without producing object code and issue error messages


• Links the program object code with other object code to produce an executable file

– i.e., link with the standard library, other libraries, object files you created (“.o” files)

• Saves the executable code on disk

– On Linux, this file is default named a.out

• If any link errors are encountered

– No executable file will be generated; error messages will be displayed

3. Linking


An Example C Program

/* Filename: hello.c

Author: Brian Kernighan & Dennis Ritchie

Description: Prints the greeting “Hello, World!”

*/

#include <stdio.h>

int main ( void )

{

printf ( “Hello, World!\n” ) ;

return 0 ;

}

Comment Preprocessor

directive

Keywords:

int void return Functions:

main( ) and printf( )

2 statements;

each ends with “;”


Our Example C Program

• The program displays the message “Hello,

World!” on screen using printf( ) function

• “int main (void)” means main( ) function

– returns an integer value

– accepts no arguments, i.e., its arg list is void

• “return 0” is to return value 0

– to the environment in which it is invoked

– indicates normal/successful end


Our Example C Program

• Within printf( ), “\n” is used to break the

displayed text line and to go to a new line

– Without the “\n”, an edit-compile-execute

session on Linux would look as follows

$ vim HelloWorld.c $ gcc HelloWorld.c $ ./a.out Hello World!$

Edit using “vim”

Compile using “gcc”

Execute a.out

Notice where the

prompt $ is now


Anatomy of a C Program

• C Language keywords

• main( ) function required in every program

• Pre-processor directives

– E.g., #include <stdio.h> so that we can use

printf( ) function

– stdio.h : standard input output header file


Anatomy of a C Program

• Comments

– Multi-line block comments within “/*” and “*/”

– Single-line comments starting with “//”

• Tokens: elements identified by the

compiler in the source code

– Keywords (also known as reserved words),

literals, identifiers and operators


C Keywords

auto break case char const continue default do

double else enum extern float for goto if

int long register return short signed sizeof static

struct switch typedef union unsigned void volatile while

Note that C is case-sensitive; so “int” is a valid keyword

whereas “Int”, “INT” and “InT” are not


Literals

(Factual Data/Constants)

• Numeric literal : an uninterrupted

sequence of digits (may contain a period)

– E.g., 123, 10000 and 99.99

• Character literal : a single character

surrounded by single quotation marks ‘ ’

– E.g., ‘a’, ‘G’, ‘$’ , ‘4’ , ‘?’, ‘{’, ‘@’, ‘+’

• String literal : a sequence of characters

surrounded by double quotation marks “ ”

– E.g., “I like ice cream.”


Identifiers

• Identifiers are also referred to as names

– Variable names, function names

– Examples: last_name, total, x1, printf, main

• A valid identifier : a letter followed by a

sequence of letters, digits or underscore

(_) symbols

• C is case sensitive identifier abc is

different from ABC or Abc


Operators

• Used with operands to build expressions

– E.g., “4+5” operands 4 and 5, operator +

• C supports a large number of

mathematical and logical operators such

as +, -, *, /, %, ^, &, && , |, ||, ?

• Symbols like {, }, (, ), [, ], ;, ;,... may also

be considered as operators

• Will be discussed later in detail


C Tokens: Summary


Python: Quick Overview

• Python : general-purpose, high-level

• Design philosophy includes:

– Code readability

– Expressing concepts in small amount of code

• Supports many programming paradigms

– Object-oriented, functional, imperative

• Has dynamic typing, automatic memory

management


How to Use Python

1. Interactive mode

– Work with the interpreter interactively

– Enter expressions, statements, commands

one at a time, and wait for the interpreter

2. Command-line mode

– “programming mode”

– Edit a Python program into a file

– Invoke the interpreter with the program file as

input


Comparing C, Python?

C Python

Time to learn High Low

Time to code a program High Low

Code size (# of lines) High Low

Efficiency

(e.g., speed) High Low


Conclusion

• We discussed

– Course details of CS1032

– Background

– Overview of C

– Quick introduction to Python

• Next time

– Continue with Python programming

• Operators, expressions


cs1032 2013batch lecture 1

Documents

sanath jayasena staff

course material course

course module

course schedule labs

pm group

course lms site

week group

distributed course notes