In some cases, we have to execute a body of the loop at least once even if the condition is false. This type of operation can be achieved by using a do-while loop. In the do-while loop, the body of a loop is always executed at least once. After the body is executed, then it checks the condition.
If the condition is true, then it will again execute the body of a loop otherwise control is transferred out of the loop. Similar to the while loop, once the control goes out of the loop the statements which are immediately after the loop is executed.
The critical difference between the while and do-while loop is that in while loop the while is written at the beginning. In do-while loop, the while condition is written at the end and terminates with a semi-colon ;. In the above example, we have printed multiplication table of 2 using a do-while loop. The general structure of for loop syntax in C is as follows:. Notice that loops can also be nested where there is an outer loop and an inner loop.
For each iteration of the outer loop, the inner loop repeats its entire cycle. Consider the following example with multiple conditions in for loop, that uses nested for loop in C programming to output a multiplication table:. The nesting of for loops can be done up-to any level. The nested loops should be adequately indented to make code readable. The break statement is used mainly in in the switch statement. It is also useful for immediately stopping a loop. When you want to skip to the next iteration but remain in the loop, you should use the continue statement.
Selection of a loop is always a tough task for a programmer, to select a loop do the following steps:. Skip to content. What is Loop in C? Types of Loops in C Depending upon the position of a control statement in a program, looping statement in C is classified into two types: 1. Entry controlled loop 2.
There are two types of loops in Python, namely, For loop, and While loop. When a loop is written within another loop, the control structure is termed as a nested loop. Therefore, when you use a loop in your program, you will not have to write the block of code written in the body of the loop , over and over again in it. The block of code will be executed as many times as the control statement will hold true and the loop will be terminated when the conditions in the control statement become false.
If the conditions are not clearly defined in the control statement, the loop will keep on executing. Such loops are termed as infinite loops. If no termination condition is provided in the control statement of a loop, then it automatically becomes an infinite loop. Hence, going through the below information will help kids to understand the concepts of loops in computer programming. There are basically two types of loops in most computer programming languages, namely, entry controlled loops and exit controlled loops.
In an entry controlled loop, the control statement is written right at the beginning of the loop. This type of loop is also called a pre-checking loop. The conditions in the control statements are checked at first, and only if the conditions are true, the body of the loop is executed. If the condition turns out to be false, the lines of code in the body of the loop will not be executed. In an exit controlled loop, the control statement is written at the end of the loop structure.
The lines of codes in the body of the loop are executed once before the condition is checked. Hence, this type of loop is also called a post-checking loop. FOR loop is an entry controlled loop, that is, the control statements are written at the beginning of the loop structure, whereas, do-while loop is an exit controlled loop, that is, the control statements are written at the end of the loop structure.
As discussed above, a For loop is an entry controlled loop. The general syntax of a For loop is given below. Body of loop;. The variables required for the control statements can be initialized in the For loop itself. This variable initialized in the For loop is called the counter and is incremented or decremented with every iteration of the loop. The condition is a boolean statement that compares the value of the counter to a fixed value, at every iteration, and terminates the loop when the condition is not satisfied.
If you test condition at the start of the loop in the Do statement , the loop might not run even one time. If you test at the end of the loop in the Loop statement , the loop always runs at least one time. The condition usually results from a comparison of two values, but it can be any expression that evaluates to a Boolean Data Type value True or False.
This includes values of other data types, such as numeric types, that have been converted to Boolean. You can nest Do loops by putting one loop within another. You can also nest different kinds of control structures within each other. For more information, see Nested Control Structures. The Do Loop structure gives you more flexibility than the While End While Statement because it enables you to decide whether to end the loop when condition stops being True or when it first becomes True.
It also enables you to test condition at either the start or the end of the loop. The Exit Do statement can provide an alternative way to exit a Do…Loop. Exit Do transfers control immediately to the statement that follows the Loop statement. Exit Do is often used after some condition is evaluated, for example in an If Else structure.
You might want to exit a loop if you detect a condition that makes it unnecessary or impossible to continue iterating, such as an erroneous value or a termination request. One use of Exit Do is to test for a condition that could cause an endless loop , which is a loop that could run a large or even infinite number of times.
You can use Exit Do to escape the loop. You can include any number of Exit Do statements anywhere in a Do…Loop.
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