THE AUTOMATED FLOWCHART DESIGN AND CODE WRITING SYSTEM

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INFORMATION ABOUT PROGRAM FLOWCHARTS

In this web page I attempt to help you understand the basic concepts and principles on which LogicCoder is built. With this knowledge, you will find it easier to appreciate the way LogicCoder works and your learning curve should be easier to climb. There are also useful information about Computer Program Flowchart, Program Logic Control Structures and the Program Development cycle. Use this link to convert your source code to LogicCoder and Ms Excel flowchart.

DIFFERENCE BETWEEN AN ALGORITHM AND A CONTROL LOGIC

There is a difference in the use of the terms "Algorithm" and "Program control logic". This is even more so in the area of Theoretical Analysis of computer algorithms. I was doing some research at one point and I made a claim that I had discovered a new algorithm for solving a problem. I wrote up the solution and gave it to my supervisor. He had a quick look at it and then tells me that he does not understand it and that I should do a proper explanation. I did a re-explanation in writing and then resubmit. Again, he said that he did not understand it and that I should properly explain it. I offer to submit a working program with a flowchart to explain but he said he did not want a flowchart or a program. Only an explanation would do. You see, a proper explanation allows correct theoretical analysis. Get a free tutorial version of LogicCoder for ANSI C/C++ and BASIC.

Algorithms are usually more attached to a specific logic problem whereas a Control Logic is more attached to a device on which an algorithm is to be implemented. You can use a flowchart to illustrate a control logic as well as an algorithm.

PRINCIPLES OF PROGRAM FLOWCHARTING

This section gives a concise introduction to the concepts and principles of flowcharting as a means for illustrating program algorithms to be executed on digital computer systems. The main objective is to help you understand the basic principles on which LogicCoder operates and to provide you with a conceptual guide for design of your program algorithms. This on-line documentation is not intended to be a detailed practical guide. Reference sources that gives more practical learning material including programming language concepts and design techniques are given at the

WHAT IS PROGRAM FLOWCHARTING?

Flowcharting is the art of illustrating program algorithms graphically using standard symbols and their interconnection. A program algorithm is the sequence of logical steps that must be executed on a machine in order to derive the solution to a programming problem.

There is no known standard accepted technique that restricts the design of program flowcharts using standard flowcharting symbols. In LogicCoder there are restrictions that the user must follow before program code can be generated by the system from a design. These restrictions may appear to be counterproductive when deriving the design for certain programming problems. In this case, the programming problem is usually trivial in nature. However, years of teaching and programming experience have shown that the advantages from the approach used in LogicCoder strongly outweigh the disadvantages. These rules ensure that all control logic structures are well defined, can be easily identified, edited or abstracted. In later version of LogicCoder we show how these rules are developed further to create data flow diagrams and for identification of parallelism in an algorithm. Hence, LogicCoder provides facilities for you to convert elements of a uni-processor algorithm to a parallel system. We define a uni-processor algorithm as an algorithm which when implemented on a Digital Computer System under the Stored Program Concept is executed in time sequence as determine by its flow of control logic. At any instance in time, the system is executing only one intended instruction or group of instructions associated with the flowchart logic. Each symbol in a flowchart except connectors and lines represents a process that can be implemented on a digital computer that operates under the stored program concept. In this system of flowcharting, there are only three basic kinds of control logic structures

Well folks! This is what program design is all bout! It is now up to you to make it as complex as you would like it to be.

We have special variation of each of these three basic control elements. For example, a select case structure is a more complex but special form of the case structure. Any program implemented on a digital computer system by way of the stored program concept can be abstracted as a sequence of processes in time order. All loops have the same basic elements but can be used to implement complex processing consisting of other control elements such as a case structure or other loops.

The manner in which these restrictions are implemented in LogicCoder are hinted at in the rules given in the following sections.

ADVANTAGES OF FLOWCHARTS FOR PROGRAM DESIGN

I have listed here, some of the advantages from using flowcharts.

• They are self-documenting.
• Allow easy review and maintenance of a software system. This results in less time spent on debugging
• Helps to develop reusable algorithmic structures hence they are useful for identifying the logic of generic systems. Hence they help the user to develop concise generalize algorithmic solutions to similar problems.
• Force careful and concise solution to the logic of a program problem.
• A simplified consistent means for developing program logic

FLOWCHARTING SYMBOLS

PROCESSING

Indicates process such as calculation, Data movement or any other kind of internal processing that affects the value of data in a program.

INPUT/OUTPUT

DECISION

Shows the point in the program execution sequence where a jump takes place base on the outcome of a tested condition. In LogicCoder, Decision symbols are used only for establishing loops, case and switch-case structures.

CONNECTOR

Shows the exit from a case, a switch-case control structure or a common point where two or more control logic merges to create a single flow path. LogicCoder uses two concentric circles to distinguish a normal connector from a Switch Case connector. The Switch Case connector is illustrated and explained below.

TERMINAL

Shows the start or end point in the flow of control logic in a single flowchart. A complete flowchart must always have only one terminal symbol that indicates its beginning and a terminal symbol that indicates its termination. LogicCoder looks for a terminal symbol that indicates the start of the flowchart when doing an interconnection operation.

PREDEFINE

INTERNAL STORAGE

Shows an output operation where data is stored internally on the computer system. This storage is usually on a mass storage device such as a Hard disk or CD ROM. LogicCoder does not use this symbol.

PAGE CONNECTOR

ARROWS

Shows the flow of program control or data flow. Flow-lines can have any one of four directions. LogicCoder does not use arrows to determine the flow of control logic in a flowchart. The way this is done is explain further on in the manual. LogicCoder provides a function that you can use to see the flow of control logic in a flowchart as determine by LogicCoder.

COMMENT

Used to show points in the program logic where comments are written for the purpose of internal documentation. LogicCoder insert comments written in this symbol into the generated source program.

A Loop Decision constitute the Entry/Exit point to a loop control structure. You use the Loop Decision symbol to quickly draw this point in a flowchart. You must then use the Fragment Structure function in LogicCoder to break this symbol into its constituent.

A case decision constitute the entry point to the case structure. Use this symbol whenever you want to quickly draw a case structure in a flowchart. Use the Fragment Structure function to break this symbol into its constituent before you try to write a source program with LogicCoder.

The Exit Connector is the exit point in a case or Switch-Case structure. A Case or Switch-Case structure must always have only one exit point indicated by the exit connector. Use the Fragment Structure function to break this symbol into its constituent before you try to write a source program with LogicCoder.

ADDITIONAL SYMBOLS USED BY LOGICCODER

LogicCoder uses additional symbols. These symbols are usually composite or variant of existing symbols. Therefore, their usage and meaning is easy to follow and understand. Composite flowchart symbols are also called compound symbols. LogicCoder provides function that allows you to fragment a compound symbol into its constituent. Composite symbols are useful for drawing large or complex flowcharts quickly. The variant symbols are listed below.

• LOOP DECISION
• CASE DECISION
• SWITCH-CASE DECISION
• START TERMINAL
• END TERMINAL
• SWITCH-CASE CONNECTOR
• ABSTRACTED PREDEFINE
• INDETERMINATE PROCESS
• INPUT-PREDEFINE PROCESS
• OUTPUT-PREDEFINE PROCESS
• PREDEFINE CASE STRUCTURE
• PREDEFINE LOOP STRUCTURE
• PREDEFINE SWITCH-CASE STRUCTURE
• PREDEFINE VERTICAL/HORIZONTAL SEQUENCE
• MULTIPLE COMMENT LINES

CONTROL ELEMENTS OF A PROGRAM LOGIC

The ability of the computer to fetch and execute instructions repeatedly, accurately and at very high speed coupled with its ability to make decision on alternative processing makes the computer appears to be a powerful device. The programmer writes code in a programming language that specifies what instruction is to be executed in a program. The kind of processing done by the basic control elements that determine branching during the sequence of program statement execution can be described as:

1. Alternative processing or
2. Repetitive processing.

Actually, both type of processing is base on a process of decision making. The difference is that the control path in one case does not lead to a repeat of processing done before. Alternative processing in a program is implemented using the control logic known as the case structure or the comparing logic structure. Loops are implemented using the loop logic structure.

EVALUATING THE CONTROL LOGIC IN A FLOWCHART

When interpreting the logic of a flowchart, traversal of this logic is from top-to-bottom, left-to-right, both right-to-left and left-to-right at case decisions, and bottom-to-top followed by right-to-left when terminating a loop. Therefore, evaluating the logic in a control structure can be determined by the basic rules that govern that structure. For example, the logic in a loop can be evaluated on the basis of the basic loop logic structure along with any other nested internal structures. We use an example program flowchart to illustrate these points.

EXAMPLE
An example program flowchart is illustrated by figure 2. In this system, a program is to be coded that reads sales persons record and then calculate sales commission base on individual sales value. A 7% commission is calculated if the sales value is greater than or equal to 500.00. Otherwise, the sales commission is calculated at 5%. The total of all commission is printed at the end of processing all sales record. The logic illustrated by the flowchart below gives a more concise description of the processes to be done on a computer system.

THE C/C++ PROGRAM CODE

THE BASIC PROGRAM CODE

Certainly! it is possible to implement the logic of a flowchart in Assembly Language using LogicCoder. In this case, the description of events illustrated in the flowchart would in most case refer to the hardware elements in the system on which the program algorithm is to be implemented.

Click the following link to see example program problem control logic illustrated with the use of flowcharts with source program in BASIC/or ANSI C/C++ generated by LogicCoder. There is also a free sample download of an evaluation version of LogicCoder with sample copy of these flowchart.

FLOWCHARTING AS IMPLEMENTED IN LOGIC CODER

BASIC RULES OF LOGIC CODER

LogicCoder is design to determine the flow of program control in a flowchart without the use of arrows on lines that interconnect symbols. You do not have to use arrowhead lines to determine the flow of program control. However, you must adhere to the following rules.

• Every control logic structure must have a single entry and a single exit point.
• The Entry point to a case or loop control structure must always be a decision
• A loop control structure has its entry and exit points at the decision
• Lines must not overlap or cross over except in the case of a loop where a single horizontal line terminates the loop on a vertical line that passes control to a Decision symbol.

DRAWING A FLOWCHART

LogicCoder provides five basic ways in which you can create a flowchart by interconnection of symbols.

1. By using the mouse to select and then click symbols into their locations in the flowchart.
2. By use of the free-mode option to attach flowchart symbols at selected points on other symbols
3. By inserting control structures from templates.
4. By editing a generic template structure so that the resulting control logic implement the required solution
5. Edit an existing Control Logic in a flowchart

The tutorial Manual gives lessons to illustrate these three methods for drawing a flowchart. Click the following link to see sample screen shots within a tutorial that teaches you how to use LogicCoder to draw a computer program flowchart for a problem solution. You can also download a free copy of this tutorial in pdf form along with a Windows version of LogicCoder for ANSI C/C++ and BASIC.

CORRECTNESS OF LOOPS AND CASE STRUCTURES

Number of decisions in a nested case structure must equal number of connectors
2. Loops must have entry and exit point at their decision
3. Case structures nested within a loop must satisfy 1 completely within the loop.
4. Loops within a case structure must satisfy 2 completely within the case structure

Using the branch point principle given in LogicCoder may appear to be inefficient in the first instance. However, over the long term you will find that it is a highly productive restriction that avoids the development of complicated or difficult to edit control logic structures. The example flowchart below illustrates a temptation to violate the basic loop design principle. In this algorithm, a data file is to be used to create a report by repetitive processing of its records.

The control logic used to implement a loop must be explicitly determine to be that of the while or do-while loop. A do-while looop control logic must not be used for the sole purpose of saving coding statements or for the sole purpose of simplifying a control logic.

The information given in these example flowcharts is only intended to be a guid of the facilities available in LogicCoder's Technical Reference Manual. This information is incomplete. More detailed explanation of program flowcharts can be found in our teaching resources and the Technical Reference Manual.

A STRUCTURED APPROACH TO PROGRAMMING

THE PROGRAM DEVELOPMENT CYCLE

The Program Development Cycle is the well-established standard approach towards the development of professional maintainable software systems. Because of the precise nature of the sequence and kind of instructions involved in the solution to a programming problem, it is important that the programmer approach the solution to a programming problem in a systematic and discipline manner. This systematic approach is called the program development life cycle. The program development life cycle consist of the following stages:

1. Review of program specification
2. Program design
3. Program coding
4. Program testing and debugging
5. Program documentation

REVIEW OF THE PROGRAM SPECIFICATION

The solution to a programming problem begins with a clear description of the problem to be solved. This includes the following:

• The format and type of input data,
• Processing to be done on the input data,
• Format of the output created from the processed data.

A clear understanding of the program specification should be the basis for the programming problem solution. At this point, the programmer should have no doubt as to the format of the input data, the processing to be done to them and the format of the output from the program.

THE PROGRAM DESIGN

THE PROGRAM CODING

THE IMPORTANCE OF PROGRAM REVIEW

It is possible that a programmer from time to time will make errors in the logic design of a programming problem solution or in the syntax use of a programming language. Therefore, it is important that other programmers review a program before it is entered into the computer system. The program review is best done by people other than the programmer. A program review is not an exercise to critiqued a program, but an opportunity for classmate, or quality control people to benefit as a result of the following:

1. A reviewed program should contain no error and will produce the correct result when it is run on the computer system.
2. The programmer will spend less time and frustration in the process of testing and correcting the program.
3. The person reviewing the program will benefit by seeing alternative approach to solving a problem. In the case where errors are discovered, the reviewer will avoid committing similar errors in their own programs.

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