<< Chapter < Page Chapter >> Page >
An introduction to control structure categories and those allowed in structured programming.

Introduction

One of the most important concepts of programming is the ability to control a program so that different lines of code are executed or that some lines of code are executed many times. The mechanisms that allow us to control the flow of execution are called control structures . Flowcharting is a method of documenting (charting) the flow (or paths) that a program would execute. There are four main categories of control structures:

  • Sequence – Very boring. Simply do one instruction then the next and the next. Just do them in a given sequence or in order listed. Most lines of code are this.
  • Selection – This is where you select or choose between two or more flows. The choice is decided by asking some sort of question. The answer determines the path (or which lines of code) will be executed.
  • Iteration – Also known as repetition, it allows some code (one to many lines) to be executed (or repeated) several times. The code might not be executed at all (repeat it zero times), executed a fixed number of times or executed indefinitely until some condition has been met. Also known as looping because the flowcharting shows the flow looping back to repeat the task.
  • Branching – A control structure that allows the flow of execution to jump to a different part of the program. This category is rarely used in modular structured programming.

All high-level programming languages have control structures. All languages have the first three categories of control structures (sequence, selection, and iteration). Most have the if then else structure (which belongs to the selection category) and the while structure (which belongs to the iteration category). After these two basic structures there are usually language variations.

The concept of structured programming started in the late 1960's with an article by Edsger Dijkstra. He proposed a "go to less" method of planning programming logic that eliminated the need for the branching category of control structures. The topic was debated for about 20 years. But ultimately – "By the end of the 20th century nearly all computer scientists were convinced that it is useful to learn and apply the concepts of structured programming. " Structured programming from Wikipedia

Introduction to selection control structures

The basic attribute of a selection control structure is to be able to select between two or more alternate paths. This is described as either two-way selection or multiway selection . A question using Boolean concepts usually controls which path is selected. All of the paths from a selection control structure join back up at the end of the control structure, before moving on to the next lines of code in a program.

We have mentioned that the if then else control structure belongs to the selection category and is a two-way selection.

If then else control structure

if (age>17) {cout<<"You can vote."; }else {cout<<"You can't vote."; }

Got questions? Get instant answers now!

Introduction to iteration control structures

The basic attribute of an iteration control structure is to be able to repeat some lines of code. The visual display of iteration creates a circular loop pattern when flowcharted, thus the word "loop" is associated with iteration control structures. Iteration can be accomplished with test before loops , counting loops , and test after loops . A question using Boolean concepts usually controls how long the loop will execute.

We have mentioned that the while control structure belongs to the iteration category and is a test before loop.

While control structure

counter = 0; while (counter<5) {cout<<"\nI love computers!"; counter ++;}

Got questions? Get instant answers now!

Definitions

control structures
Mechanisms that allow us to control the flow of execution within a program.
sequence
A control structure where you do the items in the sequence listed.
selection
A control structure where you select between two or more choices.
iteration
A control structure that allows some lines of code to be executed many times.
branching
A control structure that allows the flow of execution to jump to a different part of the program.
structured programming
A method of planning programs that avoids the branching category of control structures.

Questions & Answers

what is mutation
Janga Reply
what is a cell
Sifune Reply
how is urine form
Sifune
what is antagonism?
mahase Reply
classification of plants, gymnosperm features.
Linsy Reply
what is the features of gymnosperm
Linsy
how many types of solid did we have
Samuel Reply
what is an ionic bond
Samuel
What is Atoms
Daprince Reply
what is fallopian tube
Merolyn
what is bladder
Merolyn
what's bulbourethral gland
Eduek Reply
urine is formed in the nephron of the renal medulla in the kidney. It starts from filtration, then selective reabsorption and finally secretion
onuoha Reply
State the evolution relation and relevance between endoplasmic reticulum and cytoskeleton as it relates to cell.
Jeremiah
what is heart
Konadu Reply
how is urine formed in human
Konadu
how is urine formed in human
Rahma
what is the diference between a cavity and a canal
Pelagie Reply
what is the causative agent of malaria
Diamond
malaria is caused by an insect called mosquito.
Naomi
Malaria is cause by female anopheles mosquito
Isaac
Malaria is caused by plasmodium Female anopheles mosquitoe is d carrier
Olalekan
a canal is more needed in a root but a cavity is a bad effect
Commander
what are pathogens
Don Reply
In biology, a pathogen (Greek: πάθος pathos "suffering", "passion" and -γενής -genēs "producer of") in the oldest and broadest sense, is anything that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ. The term pathogen came into use in the 1880s.[1][2
Zainab
A virus
Commander
Definition of respiration
Muhsin Reply
respiration is the process in which we breath in oxygen and breath out carbon dioxide
Achor
how are lungs work
Commander
where does digestion begins
Achiri Reply
in the mouth
EZEKIEL
what are the functions of follicle stimulating harmones?
Rashima Reply
stimulates the follicle to release the mature ovum into the oviduct
Davonte
what are the functions of Endocrine and pituitary gland
Chinaza
endocrine secrete hormone and regulate body process
Achor
while pituitary gland is an example of endocrine system and it's found in the Brain
Achor
what's biology?
Egbodo Reply
Biology is the study of living organisms, divided into many specialized field that cover their morphology, physiology,anatomy, behaviour,origin and distribution.
Lisah
biology is the study of life.
Alfreda
Biology is the study of how living organisms live and survive in a specific environment
Sifune
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Programming fundamentals - a modular structured approach using c++. OpenStax CNX. Jan 10, 2013 Download for free at http://cnx.org/content/col10621/1.22
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Programming fundamentals - a modular structured approach using c++' conversation and receive update notifications?

Ask