Prelims Handouts

8/3/2019 Prelims Handouts

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PROGRAM

A set of instructions given to a

computer which the computer will

do or follow Also called as Software


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Note:

Software is not just theprograms but also all

associated documentation andconfiguration data which is

needed to make theseprograms operate correctly.


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Programming

The act of preparing

or writing a program

using a particularlanguage called aprogramming

language.


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Programmer

Someone who does the

programming or the act

of creating a program. It could be you or

someone who already

knows how to programa computer.


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Types of Software


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System Software

The kind of software that controls and

takes care of the working computer

and overall functioning of the system. The best example of system software

is the operating system

Ex. Windows XP, Windows ME,Windows XP, Linux, Unix,Apples OS


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Application Software

Software that generally suited to

perform a particular task or

function Ex. Word Processor,

Spreadsheet, Computer Games,

Desktop Publishing Software andGraphics Program


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Types of Productionof Software


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Commercial Software

These are created and marketedby big software companies

Usually made by a team of expertsand computer professionals andare sold for quite a big price

Ex. Microsoft Windows OS, MSOffice


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Shareware

Because of the high cost of

software, many individual

programmers made shareware Shareware, however is not really

shared but is lent or allowed to be

tested for a time before a fee isrequested


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Freeware

Given for free or allowed to be

downloaded from the Internet.

Programmers who createfreeware do it as a service to

users who cannot afford

programs


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Designing a Program


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1. Determine Your

Objectives Reason why you need to createthe program

Define what the problem is


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2. Devise a Method to

Achieve your Objective Break the problem into logical

steps to achieve the solution You can use the flowcharts

Type of approach


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3. Write your Solution orMethod as a Computer

Program

Use a particularlanguage to

code yourprogram


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4. Run and Test the

Program Debugging the process of

checking and correcting theerrors

Bug (Error in the computertermed by Grace Murray Hopper)


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Lady Augusta Ada

First programmer

Countess of Lovelace, Daughter

of Lord Byron, Credited with innovating the loop,

or repetition in Analytical Engine


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Types of Test

Unit Tests each program istested individually

Integration Tests checks unitshave been combined correctly

System Tests to see whetherthe overall system functionscorrectly


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Types of Errors Syntax Errors caused by incorrect

punctuation, misspelled reserved wordsand so on.

Run-Time Errors division by zeroand integer overflow that occurs during

execution. Logical Errors difficult to detect coz

the program executes but does not

produce correct results.


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Programming Language

A notation for expressing instructions to becarried out by a computer.

A medium of communication between thehuman and the machine and often,between one human being and another.


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Reasons for Studying

Increased capacity to express ideas

Learning new data structures, algorithms,

and other language features will allow aprogrammer to create more efficientprograms

Example: after learning object-oriented

programming in Java, a C programmer couldsimulate objects using structures and functions


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Improved background for choosingappropriate languages

Without having studied several different

languages, programmers will tend to stickwith the first language they learned

Example: A C programmer might implement abinary tree with arrays, instead of using theobject-oriented capabilities of Java


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Increased ability to learn new language

Knowing the basic concepts of programming

languages allows one to learn a newlanguage easier

Example: C++ or Ada programmers, who alreadyunderstand the concept of object-oriented

programming, will have an easier time of learningJava then programmers have never used theseconcepts


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Better understanding of the significanceof implementation

Knowledge of the basic concepts ofprogramming languages enables theprogrammer to make more efficient choiceswith implementation and to find bugs easierin a program

Example: A C programmer who understandspointers can create the binary tree usingstructures and pointers, instead of with arrays,and will have an easier time debugging programsthat use pointers


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Overall advancement of computing

Knowing the advantages & disadvantages

of different languages helps those incharge to choose better languages over

poorer ones

Example: In the early 1960s, Fortran was used

much more than ALGOL 60, even thoughALGOL 60 had much better control statementsthan Fortran


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Classification ofProgramming

Language


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Machine Language Language of every computer

The lowest level since it is machine-specific and is not designed for aspecific structure of a problem

Equivalent to the instructions foroperating the home appliances butcomputers are usually written incodes of a sequences of 1s and 0s


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Assembly Languages

Structurally similar to machinelanguage except that the sequences

of 0s and 1s are replaced bymnemonic names for the operatorpart of the instruction and numeric

and alphabetic symbols are used forthe operands but still low-level


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High-Level Languages Higher than machine and assembly

Have program structure divorced from

the structure of the machine that executethem

Designed to facilitate the writing of

solutions to problems they are designedto solve

Ex. Pascal, COBOL, BASIC, Fortran


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Declarative Language

The most English-like programminglanguage in its most expressive

power and functionality The highest level of language to its

counterparts and focuses more on

Object-Oriented Programming Ex. VB, Java, C++, Smalltalk


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Most UsedProgrammingLanguages


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Assembler Languages

Uses: detailed control of

hardware, used for internal

computer control and operations Description: fast, efficient but

require considerate effort and

skill; has small program size


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BASIC BeginnersAll-purpose Symbolic Code

Used mainly in education, business

and at home Description: Easy to learn, but being

nonstructured led to spaghetti style

code, but later versions have updatedto structured style


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C

Uses: for systems and general

programming

Description: fast, efficient, andwidely used, and popular among

professional programmers


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C++

Uses: for systems and generalprogramming; commercialsoftware development

Description: developed from C,adding the advantages of object-

oriented programming and morefeatures such as streams


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COBOL

COmmon Business OrientedLanguage

Used for business programming

Description: Oriented towardsbusiness and commercial applications

not so easy to learn as it is quitewordy; widely used on mainframes


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FORTRAN

FORmula TRANslation

Used for scientific, mathematical

and computational work Based on mathematical formulas;

popular among engineers,scientists and mathematicians


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Java

Developed for consumerelectronics; used mainly for many

interactive Web sites Multipurpose object-oriented

language similar to C++ but is

simpler; may also be used inother platforms


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LISP

LISt Processing

Used for artificial intelligence

Symbolic language that is difficultto learn; widely used in

universities and scientificresearch


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PASCAL

General-purpose language

Highly structured; easy to learn

and widely used for teaching inprogramming in universities


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PERL

Practical Extraction and Report

Language

Used for systems programmingand web development

Text and files are easily handled


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PROLOG

PROgramming in LOGic Used in artificial intelligence

Symbolic logic programmingsystem

It was intended for theorem

solving but it is now used inartificial intelligence


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Generations of PLs


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First Generation

In 1940s and early 1950s, all codingwas done in machine language

Every machine has its own built-in

code and this first generation ofsoftware every task was coded fromscratch.

It includes all low-level languages likemachine and assembly


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Note:

The word wasnt programming then,

but coding and programmers were

coders

The word programmer originated inEngland, and when it finally crossed

Atlantic in early 1950s it becamemore popular than coder


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ACM

Association for Computing

Machinery

First formed for coding communityin1947


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Grace Murray Hopper

First coined the term bugs

computing errors and debugging

removing the errors

While investigating Mark II computerwas not working, discovered small

moth in the machine and removed itwith a tweezer


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Mark III

Developed by Howard Aiken

First to have a coding machine


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Second Generation

The development and distribution of

machine-code subroutines,

interpretive routines, automatic codegenerators and assemblers

Ex. ALGOL-60, BASIC, COBOL and

FORTRAN


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BINAC

Binary Automatic Computer

Developed by Mauchly and Eckert

Short-Order Code a set ofinterpretive subroutines stored inmemory developed by Mauchly for

BINAC


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Third Generation

High level language that came outand perfected in the late 1960s up

to present Ex. Procedural, functional logic and

object oriented languages such as

Pascal, ADA, Lisp, Prolog, C++,Smalltalk and etc.


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Fourth Generation

Domain specific languages

Ex. Visual Basic, Delphi, Visual

Age, C++ Also languages for database

systems like SQL, Access,FoxPro, dBase and etc..


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Evaluation Criteria of

PLs


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General Criteria

Readability is it easy to read

and understand a program or

portion of a program written in thelanguage?

Writability Is it easy to write

programs in the language?


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General Criteria

Reliability does the program

help prevent errors?

Cost how expensive is it todevelop, use and maintain

programs written in the language


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More Extensive Criteria

Simplicity Is there one (or few) wayof expressing a concept?

Orthogonality are there facilitieshighly independent. i.e., if there is afeature for sequence control, then no

additional facility for sequence controlshould be present in the language?


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Adequacy Is it possible to express thesolutions to all problems to be solved in it?

Syntax is the syntax clear and

understandable? Redundancy Is there facility to guide

programming by detecting and diagnosing

inconsistencies of the programmer

M E i C i i


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Abstraction Is there a way to take virtuallyany internally consistent theme of a program,describe it, name it and use only the name

subsequently? Assertions Does the language have a

facility to state propositions that should holdregardless of the details of implementation(also called predicates, invariants, orproperties)


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Hierarchical Decomposition Isthere a facility to express a top-downanalysis of programming task?

Modular Decomposition Is there afacility to express program units that

may be semi-independently written orexecuted?


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Sequencing Is there a facility tocontrol the sequence of events

during computation, fully or partially? Data Manipulation Is there a

facility to carry out primitive

operations on the data?


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Flowchart

- pictorial representation of the logical

steps it takes to solve a problem


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Algorithm

It is a finite set of instructions that specifya sequence of operations to be carried outin order to solve a specific problem orclass of problems

Pseudocode


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Pseudocode-English-like representation of the same

thing.

-Pseudois a prefix that means false

-Code program is to put in a programminglanguage

-False code or sentences that appear tohave been written in a computer

programming language but dont necessarilyfollow all the syntax rules of that language


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Types of Flowchart

Program Flowchart It describesgraphically in detail the logical operationsand steps within a program and the

sequence in which steps are to be executed System Flowchart a graphic

representation of the procedures involve in

converting data on input media to dataoutput form


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Flowcharting Symbols

and Usage

Input/Output Symbol


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Input/Output Symbol(Parallelogram)

It is used to depict an input/output medium

which is not specific. This is used in a logicflowchart.

Processing Symbol


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Processing Symbol(Rectangle)

It represents a group of instructions thatperform a processing function of aprogram

Decision Symbol


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Decision Symbol(Diamond)

It denotes a point where more than one pathcan be taken. It is based upon conditions, abranch to alternative paths is possible .

Preparation Symbol


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Preparation Symbol(Hexagon)

It is used to represent an instruction orgroup of instructions that will alter ormodify a program.

Terminal Symbol


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Terminal Symbol(Oval)

It is used to designate the beginning andthe end of a program.

Pre Defined Processing Symbol


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Pre-Defined Processing Symbol(Rectangle with two vertical lines)

It is a specialized symbol representing anamed operation not explicitly detailed

On-Page Connector


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On Page Connector(Small Circle)

It is non-processing symbol used to

connect one part of flowchart to anotherwithout drawing flowlines.

Fl li


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Flowlines

Signifies the process that is to beexecuted next

Off-Page Connector


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Off Page Connector(Small Pentagon)

It is used to designate entry to or existfrom a page when a flowchart requiresmore than one page.

Punch Card Symbol


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Punch Card Symbol(Rectangle with Notch)

It denotes for all types of card used.

P i t d D t S b l


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Printed Document Symbol

It denotes any written information on paper.It could be a source of document fromwhich data is collected or final output

Magnetic Tape


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Magnetic Tape(Circle with line)

It is used as an input/output symbol formagnetic tape files

On-Line Storage/


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On Line Storage/Magnetic Disk

It is used if the file is read/recorded on amagnetic disk

V i bl


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Variable

A character or group of characters thatrefers to a value and in the of acomputer program, corresponds to an

address

R l i N i V i bl


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Rules in Naming a Variable

Variable names must be one word

Variable names must have some meaning

T f V i bl


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Types of Variable

Numeric Value

Character, text or String Variables


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Notations Commonly

Used in Flowcharting

A ith ti O ti


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Arithmetic Operations

+ Addition

- Subtraction

* Multiplication/ Division

R l ti l O t


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Relational Operators

= Equal to

> Greater than

< Less than

Not equal to

>= Greater than or Equal to


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Logical Operators

&& AND

II OR

! NOT

Other Operators


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Other Operators

EOF End of File

OAF Open All Files

CAF Close All Files

END End

START Start

Basic Control Structure


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Basic Control Structure

Sequence

Selection or Decision (If-Then-Else)

Repetition Looping) /Do-While

Sequence


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q

Process is executed from one to

another in a straightforward manner

Selection (If-then-else)


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Se ect o ( t e e se)

A choice is provided between two

alternatives

Repetition/Do While


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Repetition/Do While

It provides for the repetitive execution of

an operation or routine while the conditionis true.

Reasons for Structure


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Reasons for Structure

Clarity as Program get bigger, they getmore confusing.

Professionalism all programmers expect

your programs to be structured.

Efficiency most newer computerlanguages are structured.

Modularity it can easily broken intoroutines

E l f S


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Design a flowchart that will acceptand display a number. Write its

equivalent algorithmsAlgorithm

Step 1. Read in the value of N

Step 2. Print the value of N

Example of Sequence

E l f S


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Draw a flowchart that will compute &display the sum of two numbers. Write

its equivalent algorithm. Initialize Sum into 0

Read in the value of A and B

Compute the sum by adding A and B Print the computed value of Sum.

Example of Sequence


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Advantages of

Flowcharts

Advantages


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Advantages

Flowcharts are language-independent, they can be learned and

applied without formal knowledge of a

programming language.

It enforces users to give attention to

significant matters over the lesssignificant ones

Advantages


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Advantages

Being graphically portrayed, itprovides an alternative to the usual

narrative description of a system or a

program

Flowcharts are easier to understand

than a program written in a particularprogramming language


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Limitations ofFlowcharting

Limitations


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Limitations

Flowcharts do not represent aprogramming language and are moreof a person-to-person than a person-

to-computer means of communication. Since thinking in graphic terms is not

normal, flowcharts cannot be viewed

as a natural means of communication.

Limitations


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Certain details often require a long

sequence of interconnected symbolswhich could easily be described in justa few lines of explanation

It does not convey why a given setoperations is made

Do not highlight the important detailssince each steps receives as muchattention

Prelims Handouts

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