Control Structure in C Programming

Control structure in C

Control structures are those programming constructs, which control the flow of program statement execution in a program. It also specifies the order of statements in the program.

In most of the programs, program statements were executed in the same order in which they were written. Each instruction was executed only once. This is not enough in programming. Sometime we may have to execute program statements based on the given condition,  we may have to execute program statements repeatedly, sometimes we may have to choose an option and perform the task accordingly. To carry out all these tasks and other similar tasks, program statements must be executed in a controlled way and it can be done using a control statement.

Mainly control structures are classified into the following three categorized

1.      Branching (selective control statement)

2.     Looping (Repetitive control statement )

3.     Jumping (unconditional control statement )

Besides these, if there is no looping/branching/ jumping then the structure is called sequential structure. In sequential control structure, program statements are executed in a sequence that is one after another.

 Decisions (Selective control statement)

In selective control structure, the selection is made based on condition. We have options to go when the given condition is true or false. The flow of program statement execution is totally directed by the result obtained from the checking condition. Hence, program statements using selective control structures are also called conditional statements. This type of control structure is mainly used for decision-making. It can mainly be categorized into two types.

Types of selective control statement

1.      Conditional statement

2.     Switch case statement

Conditional statement / Control statement

It is the most common decision making control structure which controls the flow of program statement execution based on the condition checked. It can be used in different forms.

Types of control statement

1.      if statement

2.     if else statement

3.     if else if statement (Multipath conditional statement/ if-else ladder)

4.     nested if else statement

if statement

This is the simplest form of conditional statement in which statements are executed if the test expression (condition) is true. When the condition is false there is no option to go within this structure; in such a situation control must get out from the structure will be executed. Read more

if else statement

This is another form of selective control structure which can handle both expected as well as unexpected situation. In this control structure, statements written in the body part of if are executed if the condition is true otherwise, statements written in the body part of else are executed. This is appropriate where we have to check the only condition. Read more

if else if statement

When we have two or more conditions to be checked in a series we can use if else if statement. It is also known as multiple conditional statements/ multipath conditional statement / if-else ladder. Read more

nested if-else statement

An entire if-else statement is written within the body of if part or else part of another if-else statement is called a nested if-else statement. It is used when a conditional is to be checked inside another condition at a time in the same program to make a decision.

Switch case statement

C switch case statement is a multipath decision-making statement that allows selection and execution of a particular block of statements from several blocks of a statement based upon the value of expression which is included within the switch statement and branches accordingly. The expression must be of an integral value. Read more

Looping

Looping is the process of executing the same program statement or block of program statement repeatedly for a specified number of times or till the given condition is satisfied. Loop the structure is used to carry out looping.

Types of looping

1.      for loop

2.     while loop

3.     do-while loop

for loop

It is the most common type of loop which is used to execute program statement or block of program statements repeatedly for a certain time. It is a definite loop. Main it consists of three expressions: initialization, condition, increment, or decrement. The initialization defines the loop starting point, the condition defines the loop stopping points and the counter helps to increment and decrement to a value of a counter variable. Read more

while loop

while loop executes the program statements repeatedly until the given condition is true. It checks the condition at first; if it is found true it executes the statements written in its body part otherwise it just gets out from the loop structure. It is also known as entry control or pre-test loop. Read more

do-while loop

It also executes the program statement repeatedly until the given condition is true. It executes the program statements once at first then only the condition is checked. If the condition is found true then it executes the program statement again, otherwise, it gets out from the loop structure. As it checks the condition at last it is also known to post-test loop or exit loop. Read more

Jumping

Jumping statements are particularly used to jump the execution of program statements from one place to another place inside a program. These statements may execute the same program statement repeatedly or skip some program statements. Following are the jumping statements defined in the C programming language.

1.      break

2.     continue

3.     goto

break statement

As its name implies, it is used to break the normal flow of program statement execution in loop and switch case statement. It allows us to exist from the innermost enclosing loop or switch case statement as a certain condition is satisfied.

Example

#include<stdio.h> #include<conio.h> void main() {      int i;      for(i=1;i<=5;i++)      {           if (i==4)           {               break;               printf("%d\t",i);           }      }      getch(); }

The program output is

When the value of i becomes then the break is encountered and control is passed to outside the loop structure

Continue statement

As its name implies, it is used to continue the normal flow of program statement execution in the loop; skipping particular iteration in the loop as soon as a certain condition is satisfied. When continue is encountered in the program (loop body) then the particular iteration is skipped and the loop will be continued with the next iteration.

Example

#include<stdio.h> #include<conio.h> void main() {      int i;      for(i=1;i<=5;i++)      {           if (i==4)           {               continue;               printf("%d\t",i);           }      }      getch(); }

Output of this program

When the value of i becomes 4 continue is encountered then that iteration for which is equal to 4 is skipped and it continues with i equals 5

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