EXPLAIN THE CONCEPT OF PROGRAMMING. Programming Languages and Program Development Copyright © 2012 Pearson Education, Inc. Publishing as Prentice Hall2

CAPE INFORMATION TECHNOLOGY

UNIT 1

EXPLAIN THE CONCEPT OF PROGRAMMING

Programming Languages and Program Development

Copyright © 2012 Pearson Education, Inc. Publishing as Prentice Hall 2

Objectives Explain what a programming

language is and how it works. Explain the development of

programming languages over the years and the benefits and drawbacks of high-level programming languages.

Explain how object-oriented languages attempt to remedy the shortcomings of earlier languages.


Objectives List several popular object-oriented

languages and explain their advantage over older languages.

List the six phases of the program development life cycle (PDLC) and explain why the PDLC is needed.


Programming Languages and How They Work

ProgrammingProcess used to create software programs

ProgrammersPeople who use programming languages to

create software applications

Programming languagesConsist of a vocabulary and a set of rules

called syntax


Programming Languages and How They Work

InterfacePoint of interaction between components,

such as the interaction between a user’s screen and the computer code, which results when running a program


Development of Programming Languages




• Compilers and interpreterso Source code—programming instructions in the

original form needed to translate a form that the computer can understand

o Code—programming instructions created by the programmers

o High-level language—language that mimics English; does not require a programmer to understand the intimate details of how hardware, especially the processor, handles data



• Compilers and interpreterso Compiler—utility program translates source

code into object codeo Executable program—code transformed

from object code ready to run programs that do not need to be altered

o Interpreter—translation program that does not produce object code—translates one line of source code at a time; executes the translated instruction


Five generations of programming languagesMachineAssemblyProceduralNonproceduralNatural



• First-generation languagesMachine language

○ Based on binary numbers○ Only programming language that a

computer understands directly○ Machine dependent



• Second-generation languageAssembly language

○ Low-level language○ Programs use:

Mnemonics—brief abbreviations for program instructions make assembly language easier to use

Base-10 (decimal) numbers

○ Must be translated into machine language by an assembler

○ Occasionally used to create device driversPrograms to control devices attached to a computer and

game console programs



• Third-generation languagesHigh-level languages—do not require

programmers to know details relating to the processing of data

Easier to read, write, and maintain than assembly and machine languages

Source code must be translated by a language translator



• Third-generation languages (con’t.)o Spaghetti code—difficult to follow, messy in

design, prone to errors due to numerous GOTO statements

o Structured programming—set of quality standards; programs more verbose but more readable, reliable, and maintainable GOTO statements forbidden Examples:

- Ada- Algol- Pascal



• Third-generation languages (con’t.)o Modular programming—dividing larger programs

into separate modules, each takes care of a specific function

o Information hiding—also known as encapsulation, modular programming makes it possible to hide details in sensitive applications

o Programming languages include:• Fortran• C


Development of Programming Languages• Procedural

languageso Provide detailed

instructions that are designed to carry out a specific action such as printing a formatted report

• Nonprocedural languageso Do not require

programmers to use step-by-step instructions



• Fourth-generation languagesNonprocedural languagesDo not require step-by-step proceduresExamples

○ Report generators (database reports)○ Query languages

SQL (Structured query language)—enables users to phrase simple or complex requests for data



• Fifth-generation languages Natural languageStill being perfectedNonproceduralUse everyday language to program



Object-oriented programming (OOP) Programming technique based on data being

conceptualized as objects○ Object—unit of computer information that

defines a data element that is used to model real-world objects

○ Attributes define the data○ Procedures or operations are called methods



Object-oriented programming (OOP) (con’t.)Class—blueprint or prototype from which objects

are madeInheritance—ability to pass on characteristics

from a class to subclasses



Program development methodsRapid application development (RAD)

○ Reuses prebuilt objects○ Possible because of OOP

Joint application development (JAD)○ Uses a team approach○ Involves end users throughout development

Agile software development techniques—use collaboration between teams to develop solutions to meet customer needs and company goals Copyright © 2012 Pearson Education, Inc.

Publishing as Prentice Hall 21

The Program Development Life Cycle

Program development life cycle (PDLC)Organized plan for managing the

development of softwareConsists of six phases, from problem

definition through program implementation and maintenance





Phase 1: Defining the problemDefine the problem the program will solveDefine the program specifications, including

decisions regarding data input, required processing, output, and the user interface



Phase 2: Designing the programProgram design—identifies components of the

program○ Top-down program design—breaks program

into small, manageable, highly focused routinesProcedures, functions, or subroutines

○ Structured design uses control structures—logical elements assembled in blocks of code that determine how subroutines will be programmed



Phase 2: Designing the program (con’t.)Basic control structures categories

○ Sequence control structure—code performed in line-by-line order

○ Selection control structure—also called a conditional or branch structure, this is a portion of code that leads to a block of code based on conditions being met

○ Case control structure—portion of code that branches to extensive conditional coding

○ Repetition control structure—also known as looping or iteration, this is a portion of code that repeats



Phase 2: Designing the program (con’t.)Algorithm

○ Combination of control structures ○ Step-by-step description of how to arrive at a

solutionNesting

○ Process of embedding control structures within one another



Phase 2: Designing the program (con’t.)Program design tools

○ Structured charts—also called hierarchy charts, show top-down design of programs

○ Flowcharts—use diagrams to show the logic of a program

○ Unified Modeling Language (UML)—variation of flowcharting used to illustrate and document object-oriented systems during development

○ Pseudocode—uses a stylized form of writing to describe logic



Phase 3: Coding the programProgrammers convert algorithms into

programming codeSyntax errors

○ Mistakes in the construction of the programming commands

○ Must be corrected for the program to run appropriately



Phase 4: Testing and debugging the programAll errors, not just syntax errors, must be

removedLogic errors

○ Relate to problems in the solution’s design○ Cause incorrect output○ Program still runs despite logic errors

Syntax errors and logic errors—bugsDebugging—process of eliminating errors



Phase 5: Documenting the programDocumentation includes:

○ Overview of program functionality○ Tutorials○ Thorough explanation of main features ○ Reference documentation of program commands○ Description of error messages○ Program design work, including structure charts,

pseudocode, and flowcharts



Phase 6: Implementing and maintaining the programTest the program

○ Have users work with the software○ Correct errors

Program maintenance○ Fix program errors discovered by users○ Conduct periodic evaluations on a regular basis○ Make modifications as needed to update the

program or add featuresCopyright © 2012 Pearson Education, Inc.

Publishing as Prentice Hall 32

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EXPLAIN THE CONCEPT OF PROGRAMMING. Programming Languages and Program Development Copyright © 2012 Pearson Education, Inc. Publishing as Prentice Hall2