cs110d: programming language i - · pdf filecs110d: programming language i lecture 1:...

CS110D: PROGRAMMING CS110D: PROGRAMMING LANGUAGE ILANGUAGE I

Lecture 1: Introduction to computers & problem solving

Computer Science department

Lecture Contents

� Course Info.

� Problem Solving Techniques� Pseudocode

� Algorithm

2

dr. Amal Khalifa,Fall14

� Flow charts

� Examples

� Elements of a Computer system.

� Evolution of programming languages

� The code Life Cycle

Course info

� Books and references

� Course plan

� Assessment methods and grading

� Labs and practical assignments

3

� Labs and practical assignments

� Practical exam

Books and references

[1] JavaTM Programming: From Problem Analysis to Program Design (Introduction to Programming) 5th Edition

� https://www.amazon.com/JavaTM-Programming-Problem-Analysis-

4

[1]

Programming-Problem-Analysis-Introduction/dp/111153053X

[2] Deitel P.J., Deitel H.M. - Java. How to Program, 9th Edition

� http://staff.cs.psu.ac.th/iew/cs344-481/Java%20How%20to%20Program%209th%20Edition.pdf

[2]

How People Solve Problems5

� A Problem exists when what we have (Data) is not the same as what we want (information)

� People create a solution (called an Algorithm) which manipulates Data into Information

Dr. Amal Khalifa, 2014

manipulates Data into Information

� People do this quickly and often in a complex way

How Computers Solve Problems6

� Computers also use Algorithms to solve problems, and change data into information

� Computers can only perform one simple step at a time


time

� Complex “Human” Algorithms must be broken down into simple step-by-step instructions BEFORE they can be translated into computer code

Algorithms7

� Algorithm: A step-by-step problem-solving process in which a solution is arrived at in a finite amount of time

� Example: Accelerating in a car1. Move right foot to gas pedal

2. Apply pressure to gas pedal with right foot


2. Apply pressure to gas pedal with right foot

3. If speed is too high, apply less pressure.

4. If speed is too low, apply more pressure.

Problem Solving8

� Problem Solving is the ability to understand what you have, what you want, and creating a set of instructions to change what you have into what you want


� Good Problem Solving Skills are based on knowledge, experience and logic

� Good Programmers NEVER make assumptions

9 Dr. Amal Khalifa, 2014

Problem Solving Approach10

� In the programming environment, the problem-solving process involves the following steps:1. Analyze the problem and outline the problem and its solution requirements.

2. Design an algorithm to solve the problem.


2. Design an algorithm to solve the problem.

3. Implement the algorithm in a programming language, such as Java.

4. Verify that the algorithm works.

5. Maintain the program by using and improving it, and modifying it if the problem domain changes.

Problem analysis–coding–execution cycle11


Expressing the Algorithms12

� A “Standard” way of describing an algorithm must exist if we expect our solution to be understood by others easily

� There are standards in programming:PSEUDOCODE


� PSEUDOCODE

� FLOWCHARTS

Pseudo Code

� “Pseudo” means “pretend” or “false”

� Pseudo Code is pretend or false computer code; generic English-like terms that are somewhat like computer code

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computer code

� Pseudo Code is not as standardized as flowcharts, and does not facilitate the breaking down of problems as well as a flowchart does


Pseudocode (wikipedia)14

� Pseudocode (derived from pseudo and code) is a compact and informal high-level description of a computer programming algorithm that uses the structural conventions of programming languages, but omits detailed subroutines, variable declarations


but omits detailed subroutines, variable declarations

or language-specific syntax. The programming language is augmented with natural language

descriptions of the details, where convenient.

Example15

� Write an algorithm to find the area and the perimeter of a rectangle


design an algorithm to find the perimeter and area of a rectangle

Pseudo Code Example16


Text book

[1] chapter 1 (pages 13-16)

That’s all for Today!!17



Flowcharts18

� Graphical representations of algorithms

� Tool to translate algorithms into software

� A Flowchart uses easy-to-understand symbols to represent actions on data and the flow of data


represent actions on data and the flow of data

� Flowcharts aid in breaking down a problem into simple steps

Flowchart Symbols19


flowcharting20


Example21

� Example 1: Write an algorithm and draw a flowchart to convert the length in feet to centimeter.

hint: I feet = 30 cm


hint: I feet = 30 cm

Pseudocode22

� Input the length in feet (Lft)

� Calculate the length in cm (Lcm) by multiplying LFT with

30


� Print length in cm (LCM)

Algorithm23

� Step 1: Input Lft

� Step 2: Lcm ← Lft x 30

� Step 3: Print Lcm

START

Input

Lft

Flowchart


� Step 3: Print Lcm

Lcm ← Lft x 30

Print

Lcm

STOP

Example 2 24

Write an algorithm and draw a flowchart that will read the radius of a circle and calculate its area.


Example 2 25

Pseudocode

� Input the radius (r) of a circle

� Calculate the area (A) :

A ← Pi x r x r


A ← Pi x r x r

� Print A

Example 226

Algorithm

� Step 1: Input r

� Step 2: A ← Pi x r x r

� Step 3: Print A

START

Input

r


� Step 3: Print AA ← Pi x r x r

Print

A

STOP

� Write an algorithm and draw a flowchart that will calculate the roots of a quadratic equation

� Hint: the roots are:

Example 327

20ax bx c+ + =

� Hint: the roots are:

x1 = (–b + d)/2a and

x2 = (–b – d)/2a

where, d = sqrt ( )


24b ac−

� Algorithm:

Step 1: Input the coefficients (a, b, c) of the

quadratic equation

Example 328

START

Input

a, b, c

d ← sqrt(b x b – 4 x a x c)

quadratic equation

Step 2: d ← sqrt ( )

Step 3: x1 ← (–b + d) / (2 x a)

Step 4: x2 ← (–b – d) / (2 x a)

Step 5: Print x1, x2

4b b a c× − × ×

Print

x1 ,x2

STOP

x1 ←(–b + d) / (2 x a)

X2 ← (–b – d) / (2 x a)

Elements of a Computer System29

Hardware


Software

Computer

Hardware30


Memory Unit31

� Ordered sequence of cells or locations

� Stores instructions and data in binary

� Types of memory

� Read-Only Memory (ROM)� Read-Only Memory (ROM)

� Random Access Memory (RAM)


Bit: A binary digit 0 or 1.

A sequence of eight bits is called a byte.

Binary Data32


ASCII Code33

Every letter, number, or special symbol (such as * or {) on your keyboard is encoded as a sequence of bits, sequence of bits, each having a unique representation.

The most commonly used American Standard Code for Information Interchange (ASCII).


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Central Processing Unit (CPU)

� Executes stored instructions

� Arithmetic/Logic Unit (ALU)� Performs arithmetic and logical

operations

Control Unit


� Control Unit� Controls the other components

� Guarantees instructions are executed in sequence

Input and Output Devices35

� Interaction with humans

� Gathers data (Input)

� Displays results (Output)


Software

� loads first when you turn on your PC

� Also called the operating system.

The operating system monitors

� perform specific tasks

� Examples :

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System programs Application programs

� The operating system monitors the overall activity of the computer and provides services, such as memory management, input/output activities, and storage management.

Examples :

� Word processors

� spreadsheets, and

� games


Both operating systems and application programs are

written in programming languages.

37

Are Computers Intelligent?

� Do we really need to be involved in programming computers?

� They have beaten world chess champions.

� They help predict weather patterns.� They help predict weather patterns.

� They can perform arithmetic quickly.

� So, a computer has an IQ of _____.


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What is Computer Programming?

� Planning or scheduling a sequence of steps for a

computer to follow to perform a task.

� Basically, telling a computer what to do and how to do it.


do it.

� A program:

� A sequence of steps to be performed by a computer.

� Expressed in a computer language.

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Computer Languages

� A set of

� Symbols (punctuation),

� Special words or keywords (vocabulary),

� And rules (grammar)


� And rules (grammar)

used to construct a program.

Evolution of Programming Languages40

� Languages differ in

� Size (or complexity)

� Readability

� Expressivity (or writability)


� Expressivity (or writability)

� "Level"

� closeness to instructions for the CPU

Machine Language41

� Binary-coded instructions

� Used directly by the CPU

� Lowest level language

� Every program step is ultimately

10010110

11101010

00010010

2034

2035

2036

Address Contents

a machine language instruction00010010

10101010

10010110

11101010

11111111

01010101

10101101

2036

2037

2038

2039

2040

2041

2042


Assembly Language42

� Each CPU instruction is labeled with a mnemonic.

� Very-low level language

� Almost 1 to 1 correspondence with machine language

� Assembler: A program that translates a program written in assembly language into an equivalent program in machine


assembly language into an equivalent program in machine language.

Mnemonic Instruction

ADD 10010011

MUL X,10ADD X,YSTO Z,20SUB X,Z

Sample Program

Examples of Instructions in Assembly Language and Machine Language

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High-Level Languages

� Closer to natural language

� Each step maps to several machine language instructions

� Easier to state and solve


� Easier to state and solve problems

� Compiler: A program that translates a program written in a high-level language into the equivalent machine language.

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Examples of High-Level Languages

Language Primary Uses

Pascal Learning to program

C++ General purpose

FORTRAN Scientific programming


FORTRAN Scientific programming

PERL Web programming, text processing

Java Web programming, application

programming

COBOL Business

The java Language46

source program.

Saved in File ClassName.java


va

The Code life Cycle!!

Edit � compile � run

47


Processing a java program48


IDE49

� The programs that you write in Java are typically developed using an integrated development environment (IDE).


Text book


That’s all for Today!!50



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