1 Programming Basics Ready

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Introducing Programming



Agenda

By the end of this lecture, you should …

Understand the different types ofprogramming languages.

Understand the basic procedures in aprogram as input, processing and output.

Understand the importance of variables.

Understand a basic map of the programdevelopment cycle.



Computer Components

CPU Central Processing Unit

RAM (Random Access Memory)

Mass storage devices

Input devices

Output Devices



Storage Units

bit – smallest capacity

nibble = 4 bits

byte = 2 nibbles = 8 bits

storage for one character

1 kilobyte (KB) = 1024 bytes

1 megabyte (MB) = 1024 KB

1 gigabyte (GB) = 1024 MB



Software

Application Software

Word Processors

Database s/w

Spreadsheets

Painting programs

Web browsers, emailprograms

System Software

Operating Systems

Windows

Macintosh OS

Unix

Linux

Drivers

Software is comprised of instructions that get a computer to perform a task.



Programming Languages

Programming languages allow programmersto code software.

The three major families of languages are:

Machine languages

Assembly languages

High-Level languages



Machine Languages

Comprised of 1s and 0s

The “native” language of a computer

Difficult to program – one misplaced 1 or 0will cause the program to fail.

Example of code:1110100010101 111010101110

10111010110100 10100011110111



Assembly Languages

Assembly languages are comprised of a setof elemental commands which are tied to aspecific processor.

Assembly language code needs to betranslated to machine language before thecomputer processes it.

Example: ADD 1001010, 1011010



High-Level Languages

High-level languages represent a giant leaptowards easier programming.

The syntax of HL languages is similar to

English.

Historically, we divide HL languages into twogroups:

Procedural languages Object-Oriented languages (OOP)



Procedural Languages

Early high-level languages are typically calledprocedural languages.

Procedural languages are characterized by

sequential sets of linear commands. Thefocus of such languages is on structure .

Examples include C, COBOL, Fortran, LISP,

Perl, HTML, VBScript



Object-Oriented Languages

Most object-oriented languages are high-levellanguages.

The focus of OOP languages is not on

structure, but on modeling data .

Programmers code using “blueprints” of data

models called classes .

Examples of OOP languages include C++,Visual Basic. NET and Java.



Compiling

Regardless of the HL Language, all HL programsneed to be translated to machine code so that acomputer can process the program.

Some programs are translated using a compiler.When programs are compiled, they are translated allat once. Compiled programs typically execute morequickly than interpreted programs, but have a slower

translation speed.



Interpreting

Some programs are translated using aninterpreter. Such programs are translatedline-by-line instead of all at once (like

compiled programs). Interpreted programsgenerally translate quicker than compiledprograms, but have a slower execution

speed.



Programming Example

Simple programming problem: Convert a price from British pounds into Dollars.

PseudocodeInput the price of the item, PoundPrice, in pounds

Compute the price of the item in dollars:

Set DollarPrice = 1.84 * PoundPrice

Write DollarPrice



Programming Example

Translating to Basic:INPUT PoundPrice

LET DollarPrice = 1.62 * PoundPrice

PRINT DollarPrice

END



Input & Variables

Input operations get data into the programs

A user is prompted to enter data:

Write “Enter the price in pounds”

Input PoundPrice

Computer programs store data in named sections ofmemory called variables . In the example above, thevariable is named PoundPrice. The value of a

variable can, and often does, change throughout aprogram.



Types of Data

Numeric Data

Integer data, I.e., whole numbers, 10 25 -45 0

Floating point data – have a decimal point 23.0, -

5.0

Character data (alphanumeric)

All the characters you can type at the keyboard

Letters & numbers not used in calculations Boolean data

TRUE/FALSE



Data Processing and Output

Set DollarPrice = 1.62 * PoundPrice

The above statement is a processing statement.Take the value in the variable PoundPrice, multiplyby 1.62, and set the variable DollarPrice to the

result of the multiplication.

Write DollarPrice

Output the value in DollarPrice to the monitor.



Hierarchy of Operations Example

Hierarchy of various operations depends upon the operatorprecedence (Priority) and their associatively (direction L to R or R to L).

Example:

3 * (6 + 2) / 12 – (7 – 5) * 3 ( ) first

= 3 * 8 / 12 – 2 * 3 Mult/Div (L to R)

= 24 / 12 –

2* 3 Mult/Div (L to R)= 2 – 6 Add/Subtr (L to R)

= -4



Data Output

Send information from the program to the screen, or

printer, or disk file.

Write DollarPrice

The computer displays the value of the variableDollarPrice to the screen and the cursor goes to

the next line.



Data Output

Write “The price in Dollars is”,

DollarPrice

The output looks like this:

The price in Dollars is 162

The text inside the “ ” is output to the user “as is,” and

it is the value in the variable that is output.



The Program Development Cycle



Programming as Problem Solving

Problem solvingprinciples:

1. Completely understandthe problem

2. Devise a plan to solve it

3. Carry out the plan

4. Review the results

Developing aProgram:

1. Analyze the problem

2. Design the program

3. Code the program

4. Test the program

5. Maintenance



Modular Programming

Determine the major tasks that the programmust accomplish. Each of these tasks willbe a module.

Some modules will be complex themselves,and they will be broken into sub-modules,and those sub-modules may also be broken

into even smaller modules. This is called top-down design



Mapping Modules

Inputs Processes Outputs

Input Variables:Principal

PercentageRate

Term

Frequency

Rate of Interest:Set Rate =

PercentageRate/100

Display: Write

FinalValue

Final Value:Set FinalValue = Principal *

(1 + Rate / Frequency) ^

(Frequency * Term)



Code Modules

A module is an independent, self-containedsection of code that performs a single task.

The main module is the module that drives

the application. It “controls” all other modules.Typically, the main module calls othermodules in order to have them perform

certain tasks.



Program Control & Modules

When the main module calls another module,program control transfers to the calledmodule. Program control get back to the main

module when the called module finishes.



Main module

Display program title and brief description of program

Call Input Data Module

Call Perform Calculations module

Call Output Results Module

End Program

Input Data module

Prompt for Principal, PercentageRate, Term, Frequency

Input Principal, PercentageRate, Term, Frequency

End module

Perform Calculations module

Set Rate = PercentageRate / 100

Set FinalValue = Principal * (1 + Rate / Frequency) ^ (Frequency * Term)

End module

Output Results Module

Write Principal, PercentageRate, Term, FrequencyWrite FinalValue

End module



Coding

Coding is done in a specific programminglanguage. In this part of the course, we willuse pseudocode. Later, we’ll adapt our

pseudocode to write in C#. Coding before finishing a solid algorithm is a

lot like putting the cart before the horse and

usually spells disaster. Time well-spent in thedesign phase will head off problems incoding!



Documentation

Internal Documentation

Comments explain to the reader the logic anddecision processes of the programmer.

Comments are ignored by an interpreter orcompiler.

External Documentation

External documentation includes a user’s guide

and, typically, a more technical system administrator’s guide.



Testing

Most of the work should be done before thephase begins – creating of a testingdocument.

Two types of testing: Testing for errors

Quality/Usability testing

Two phases of testing: Alpha testing (Internal testing)

Beta testing (Testing at the customer site w/ livedata)



Questions?

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