IST 153

Chapter 1 Assignment Page

 Program Development Cycle

The Program Development Cycle (PDC) steps are the steps that are followed to design and develop programs. They are performed during the fourth phase (Develop the New System) of the System Development Life Cycle. This portion of the course will focus on step 1 and step 2 of the Program Development Cycle. Although the textbook covers the System Development Life Cycle, covering the topic in the course may confuse the focus of the course. The discussion of the PDC sets the tone for the entire course. You need to realize that most of time in the Program Development Cycle should be spent designing the program. The more time they spend designing, if the design is correct, the less amount of time they will spend debugging the program. This can be compared to building a house without a blueprint.

Steps of the Program Development Cycle

Step 1: Review the program requirements – the programmer reviews the requirements defined. The programmer must read the requirements of the program and ensure they are clear. If anything is unclear at this point, the programmer asks for more information. The programmer must not make unfound assumptions. NOTE: In this textbook, the program requirements are given. You need to be able to carefully read the requirements and make sure you understand the problem you are asked to solve. You need to list the input given, the output requirements and any necessary formatting, which includes headings, line spacing, columns. The exact formatting for line spacing and columns are specified when the program is written. You should keep in mind you are designing a program for someone else and should design the program to meet their needs.

Step 2: Develop the Program Logic - the actual processing steps within each program in the system are developed. This step is the focus of the book. There are many tools that can be used to design a program. This book focuses on flowcharting and pseudocode. Program flowcharts graphically depict the problem-solving logic using standard symbols. Psuedocode consists of English-language statements that describe the processing steps of a program in paragraph form. NOTE: Normally you do not need to design the program twice. Both design tools will give the same result. In the beginning chapters of the textbook, both design tools will be used to teach a graphical and a nongraphical design tool. Flowcharting is a preferred design tool for visual learners. Flowcharts give you a graphical overview of the entire program. Following a flowchart is similar to following a map to get from one location to another. Pseudocode is a design tool that is preferred by some people because it closely resembles a programming language. It is easier to transfer a pseudocode design to a language than to transfer a flowchart to a language. When designing programs, you should design each problem using both design tools. You should use both design tools for the first 5 chapters and then choose a design tool. During the last portion of the course, you will be required to solve a problem using one design tool once you have selected a design tool. If you choose flowcharting, you may need to convert the flowchart to pseudocode before you write the program. The textbook mentions the hierarchy chart, this topic will be discussed in detail in the chapter on modules.

Step 3: Write the program – After the program logic has been developed, it must be expressed in a programming-language form. The selection of the language depends on the type of application and on the software development tools available. In the past, most business applications were written in COBOL, since it is oriented to business use. Now, more structured languages such as Pascal and C are more frequently used because they contain language elements that closely parallel the structures used in program design. NOTE: The programming language COBOL has been very prevalent in the news lately because of the Year 2000 problem. There are hundreds of programming languages. Some of the languages disappeared as quickly as they appeared on the market because of the lack of support by business and industry.

Computer programming languages are either procedure-oriented (procedural) or nonprocedural. With procedure-oriented languages, a programmer must specify the exact steps the computer needs to follow to solve a problem. Nonprocedural languages include most fourth generation languages. With fourth generation languages (4GLs), a programmer defines what needs to be done and not how to do it.

With the increased use of applications containing graphical user interfaces, visual languages such as Visual BASIC and Visual C++ have become popular. These languages support the concept of event-driven programming. An event-driven program is one that is designed to respond to actions that occur when the program is executing. For example when a user clicks on the OK button, a click even is initiated.

The widespread use to the Internet has been accompanied by rapid growth in the use of a relatively new programming language known as Java.

Step 4: Test and Debug the Program – Once the program is written using a programming language, the program must be typed in the computer system using software called a compiler. The compiler is a program that converts the programming language statements to binary code and checks them against the syntax of the language. Syntax errors occur when the programmer does not follow the rules of the language he or she is using. For example, many statements in C must end with semicolons. If the programmer forgets to enter a semicolon, he or she makes a syntax error. Such errors are easy to fix. You need to use a reference manual for the language and look up the correct syntax for the statement and make the necessary corrections. A logic error occurs when a step in the program logic is incorrect. For example, an averaging program to average the sum of 5 numbers will produce the wrong answer, if the sum of the numbers is divided by 6. Such errors are not always easy to detect. The programmer may need to go back and review the logic created in the second step of the program development cycle in order to locate the error. The program must be tested using sample data that covers all possible conditions. NOTE: Syntax errors are easy to correct and usually are caused by typing errors. However, logic errors are more difficult to correct because not all people think logically. It is usually easier for another person to find your logic error. Other people will be far more critical of your programs. You may spend days trying to find an error in a program and giving it to someone else may take a few minutes to find the error.

Step 5: Complete the Program Documentation – Documentation is an ongoing process that occurs throughout the program development cycle. A technical reference needs to be created for programmers who may need to modify one or more of the programs. User guides need to be created to tell users how to use and operate the system. Documentation can either be in printed form or on-line. This is the type of documentation you see on the screen when you type help to aid you in using a computer system.
  1. Basic Control Structures
Structured programming is the ability to express a problem solution using only three basic patterns of logic. These patterns are referred to as control structures. The patterns are based on the computer’s ability to execute instructions step-by-step (sequential manner); its ability to make decisions; and its ability to repeat instructions. The three patterns are referred to as SIMPLE SEQUENCE, IFTHENELSE, and DOWHILE.

Simple Sequence – represents the computer’s ability to execute instructions in a step-by-step, sequential manner. A simple sequence example is to give a friend directions to your house. The steps must be followed in a sequential manner, otherwise your friend might get lost.
    1. Proceed down Main Street for two miles.
    2. Turn left on Ocean Drive.
    3. Proceed on Ocean Drive for three blocks, to the fork.
    4. At the fork, take Swan Street to the left.
    5. Proceed two blocks.
    6. House is second on the left (246 Swan Street).
Selection (If Then Else) - represents the computer’s ability to make a decision. Suppose the fork in the road is blocked and your friend needs to take another route.
    1.      Proceed down Main Street for two miles.
    2.      Turn left on Ocean Drive.
    3.      Proceed on Ocean Drive for three blocks, to the fork.
    4. IF left turn at fork is blocked THEN
    Take right turn at fork onto Eagle Street.
    Proceed five blocks.
    Turn left at Clifton Avenue.
    Proceed two blocks
    Turn left at Swan Street.
    House is fourth on the right (246 Swan Street).
    ELSE
       At the fork, take Swan Street to the left.
       Proceed two blocks.
       House is second on the left (246 Swan Street).
    END IF
 Iteration (DOWHILE) - represents the computer’s ability to repeat a series of instructions. A series of repeated instructions is called a loop.
    1. Wash hair
    2. Rinse hair
    3. Repeat from step 1.
These steps would be repeated forever. This is an infinite loop. You would have to add to these steps a statement that indicates the number of times the loop should be performed. You could indicate to perform the loop two times or until the hair is clean.

Exercises: The problems in Chapter 1 are essay.