Block diagram is a graphical representation of a process, clearly showing a systematic sequence of all phases of the task, as well as all groups that are involved in this process.This scheme is a system of graphic symbols (blocks) and transition lines (arrows) between them.Each of these blocks corresponds to a particular step of the algorithm.Inside this character describes the action.
Why use flowcharts?
These systems are designed to perform the following functions:
- to develop a new process;
- describe and document the current algorithm;
- to develop modifications to the process or to investigate links with the likelihood of errors and failures;
- to determine when, where and how you can change the current algorithm, in order to verify the stability of the entire system.
Development flowchart
Any block diagram is based on the algorithm of actions describing the operation of the device or program.Therefore, we first constructed the system itself."Algorithm" referred to the description of the sequence of operations for the task.In fact, this rule perform the necessary processing information.Before the construction of the algorithm is required to clearly identify the problem, what you need to get a result, some background information is needed and what is available, whether there are restrictions on its receipt.After that, a list of actions to be implemented to achieve the desired result.
types of algorithms
In practice, most often used the following types of block diagrams:
- graphics, ie are based on geometric symbols;
- verbal: drawn up by the usual words of a language;
- pseudocode: is a semi-formalized description conditional algorithmic language that includes elements of language and literary phrases and common mathematical symbols;
- program: to write programming languages are used exclusively.
block diagram: description
Graphical representation of workflow includes an image of the algorithm describing the connection of functional blocks of the scheme, which correspond to the implementation of one or more actions.A block diagram of an array composed of individual elements, dimensions and construction rules that are defined standard state.For each type of action (input, computing expression values, checking conditions, controls a repetition of operations, and other end of the processing.) There is a separate geometric figure represented as a block.These symbols are connected by lines that define the sequence of actions.
basic elements that are used in the preparation of flowcharts
complete list of graphic symbols used to describe the algorithm consists of 42 elements.Its all we do not give, and consider only the principal.
elements flowcharts:
1. The process of computing means action or sequence of actions that change the value data placement and form of presentation.For clarity schemes such elements can be combined into one unit.This symbol is a rectangle, within which written comments accompanying the operation (or group of operations).
2. Decision.This block is used to indicate the transition control under certain conditions.In each such member states question the comparison or condition that defines it.In other words, the decision - a choice of direction for the program or algorithm depending on some variable conditions.Graphical view of the element - a diamond.Said character can be used as a unified image of the following structures: choice crossroads complete and incomplete, the cycle of "before" and "is."
3. Modification.This block is the beginning of the cycle.It is used for the organization of a cyclic structure.Inside this element record setting range of actions indicates its initial value, boundary conditions, and a step change in the parameter for subsequent recurrence.In other words, a modification - is to fulfill the changing teams or groups of operations, changing the program.Graphical representation of the symbol is a hexagon.
4. The predetermined process is the calculation of the set, or the standard program.It is used to indicate to the auxiliary treatment algorithm that exists autonomously as separate independent modules, as well as to refer to library routines.Graphically, this kind of character is represented by a rectangle with two vertical bars on the sides.This element is used to indicate references to functions, procedures, software modules.
5. Input-output data in general.
6. Start and stop.This element represents the start and end of the algorithm, as well as entry into the program and exit from it.Graphically, this symbol resembles a rectangle where the side instead of straight - arc.
7. The document is the output of your print.Graphically an element resembles a rectangle, but instead of the lower half-wave of the line traced.
8. Manual input means start data processing operator using a device that is paired with your computer (keyboard).Graphic symbol of manually entering a rectangle whose sides are parallel lines, perpendicular to their lower, upper and oblique.
9. The display indicates the input or output information when the device is directly connected to the processor.At the time when they begin to reproduce the data, the operator can make changes during processing.Graphically, this element is the figure at which the lower and upper parallel line, right - it is the arc, while the left is made up of two straight as an arrow.
10. The flow lines - are arrows that indicate the sequence of connections.Neither a block diagram of the structure can not do without this element.There are certain rules mark these characters.Here they are:
- these elements must be parallel to the lines of the outer perimeter or boundary of the page, which shows the block diagram;
- direction of the line from top to bottom or left to right is considered the main, it is not indicated by the arrows, the other cases specified areas designated by them;
- change of direction of this element is only at 90 °.
11. Connector.This element is intended to indicate a broken connection to the flow lines.These symbols are used if the block diagram of the program is constructed of several parts.Then the line of flow from one part to end "connector," and the new part - start with this character.Inside this element is placed the same serial number.Graphical representation of "connector" - a circle.
12. Interstitial connector.The purpose of this element is similar to the previous one, only it is used to connect the block diagrams, placed on different pages.The image of the element is represented by a pentagon as a house.
13. Comment - is the relationship between the various elements of the block diagram with explanations.Said element allows include formulas and other information.
Building Block Diagram Graphical
algorithm - is part of the documentation for the device or program that is always there in abundance.However, in most cases, the software does not need flowchart.Only a few require the construction of an algorithm takes a few sheets, the rest is quite symbolic scheme.A simple block diagram showing a structure of branching program in only one aspect.However, even such a structure is clearly visible only under the condition that the algorithm is placed on one sheet.In the opposite case, when the block diagram is located on several pages related interstitial transitions, very difficult to get the right idea about it.If it is placed on a single sheet, then a great program this algorithm transforms the image in its general plan with a list of the main blocks and stages.Of course, this schedule should not be standard procedure design, but he did not need them, since the process is completely different.Rules concerning the type of symbols, arrows and numbering order, are only required to parse a detailed block diagram.
Arrays and construction of algorithms
array is a set of the same type of information that is stored in successive clusters of memory and has a common name.Such cells are referred to as "system components".All clusters are numbered in order.This number is called the "index of the array element."How to create a flow diagram for such a system?Consider the example of the creation of an algorithm for the elementary one-dimensional array type.The simplest system is a schematic view of a line.Define a name for the array - "A".We assume that our system is composed of eight cells (1 to 8).Each of these clusters contains a random number, which is called the "element of the array."To access a particular cell must specify the name in square brackets ([3]).Consider an example in which a block diagram of an array is designed to fill the system with random numbers and then output the information on the screen.What is an algorithm?This elementary system.In fact, it has no practical use, but is suitable for the learning process.Considered flowchart (example of the construction described below) comprises seven main elements connected by lines transitions.
description of the sequence of the task
1. The first element of the scheme will be a symbol of "Home."
2. The second unit - "Process", which fits within the "initialization random».
3. The next element - "Modification", the value is entered in the unit cell array.
4. Further, according to a given function, is redirected to the next block of the "process", which is defined by reference to specific clusters of indicating the limits of random numbers in the range of zero to one hundred.Following the operation, there is a return to the third block, and through it - then the fifth.
5. In this section, "modifications", according to the inscribed function is redirected to the next item.
6. «Output" produces display information about the new contents of the array on the screen, followed by the direction of the previous block.Next - the last element.
7. «The End" of the algorithm.
On the basis of a block diagram of components of the program, which will provide work of the algorithm.
«flowchart editor»
If you are wondering about how to create a flowchart, you should know that there are special programs that are designed to create and edit these systems.Convenience graphical display algorithm is that the user is not tied to a specific programming language syntax.Built block diagram equally suitable for all languages (such as C, Pascal, Basic, etc.).In addition, the editor can be used for charting and verify that the schemes.This program is a specialized software.It offers a diverse set of tools required to build flow charts, which makes it more convenient, compared to conventional image editors.Additional options allow you to optimize the process of drawing up the system to further its transformation into the functions and procedures of the programming language.In addition, the editor of a block diagram of a set of templates that can significantly speed up the novice user.It is known that the construction of the algorithm often used repetitive structures, such as various variants of cycles, alternatives (complete and incomplete), multiple branching, and more.The editor allows you to select frequently used in the block diagrams elements and add them to the newly created scheme.This saves you from drawing them from scratch each time.Furthermore, using the editor can import functions and procedures implemented in any known programming language.This option is useful for analysis of the structure of the algorithm, which is written in an unfamiliar language.System Requirements considered modest program that allows you to use it on any personal computer.
Conclusion In summary, it should be noted that the detailed circuit construction of algorithms have become obsolete.As a description of the process, they are not interesting.At best, block diagrams are useful for training beginners who do not know how to think algorithmically.Proposed in his time with the elements of its content is the language of high-level language statements they combined machine in separate groups.At the moment, each graphic element corresponds to a particular operator.So, he became a symbol of the random, and most importantly - a futile exercise in drawing, which can be easily refuse.Today even become redundant line transitions, since each operator is already defined.In fact, graphical algorithms to build greater triumphs than in practice.Programmer with extensive experience before you write a program that rarely draws a block diagram.When the standard of organization requires a graphical algorithm, then paint it after the work is completed.
