In programming, a loop is an instruction that repeats until a specified condition is reached. In a loop structure, the loop asks a question, if the answer requires action, it is executed. The same question is asked again and again until no further action is required. Each time the question is asked it is referred to as iteration.
Usually a looping process entails:
- Setting and initialization of a condition variables.
- Execution of the statements in the loop.
- Test for a specified value of the con variable for execution of the loop.
- Incrementing or updating the con variable.
Types of Loops
Three major types of loops include:
- A Do While Loop also referred to as Repeat Until Loop, it repeats until an expression becomes false.
- For Loop which is a loop that runs for a preset number of times.
- While Loop which is a loop that is repeated as long as an expression is true. An expression is a statement that has value.
A program loop is made up of two segments, that is, the body of the loop and control statement. The control statement tests certain conditions and then directs the repeat execution of the statement s contained in the body of the loop. Now, depending on the position of the control statement in the loop, a control structure may be classified as either entry controlled loop or exit controlled loop.
What Is Entry Controlled Loop?
An entry control loop refers to a structured sequence of operations that control the flow of execution when entering a particular section of code or a function. The purpose of an entry control loop is to set up the initial conditions and manage any necessary resources before executing the main logic.
In other words, an entry control loop, controls entry to the loop and thus why it is referred as entry control loop. An entry control loop checks the condition at the time of entry and if the condition or expression (statement that has value) becomes true then control transfers into the body of the loop. Examples of exit controlled loop include, For Loop and While Loop.
What You Need To Know About Entry Controlled Loop
- Entry controlled loop is a loop in which the test condition is checked first, and then loop body will be executed.
- In entry controlled loop, if the test condition is false, loop body will not be executed.
- Examples of exit controlled loop include, For Loop and While Loop.
- Entry controlled loop are used when checking of test condition is mandatory before executing loop body.
The components of an entry control loop typically include:
- Entry Point: This is the starting point of the code section or function where the control loop begins execution.
- Pre-Processing: In this step, any necessary initialization or setup tasks are performed. It may involve declaring and initializing variables, acquiring resources, or performing other preparatory operations.
- Input Handling: If the entry control loop involves processing user input or external data, this component is responsible for receiving and validating the input data.
- Error Handling: At this stage, the code checks for potential errors or exceptional conditions that may arise during the processing of input data or resource allocation. Appropriate error handling mechanisms are put in place to ensure graceful handling of unexpected situations.
- Main Logic: This is the core functionality of the entry control loop. It executes the primary tasks associated with the code section or function.
- Resource Management: If the entry control loop acquires resources during its execution, this component manages their allocation and deallocation to prevent resource leaks and ensure efficient utilization.
- Post-Processing: Once the main logic is executed, this component performs any necessary clean-up tasks or additional processing before the control loop exits.
- Exit Point: This is the point where the entry control loop completes its execution and hands over control to the calling code or function.
What Is Exit Controlled Loop?
An exit-controlled loop, also known as a post-test loop, is a loop structure where the loop condition is evaluated after each iteration. The loop continues to execute as long as the loop condition remains true, and it terminates when the condition becomes false.
In other words, an exit control loop, controls exit of the loop, thus why it is referred to as exit control loop. An exit control loop checks the condition for exit and if given condition for exit evaluate to true, control will exit from the loop body or else control will enter again into the loop. An example of exit controlled loop is Do While Loop.
What You Need To Know About Exit Controlled Loop
- Exit controlled loop is a loop in which the loop body is executed first and then the given condition is checked afterwards.
- In exit controlled loop, if the test condition is false, loop body will be executed at least once.
- An example of exit controlled loop is Do While Loop.
- Entry controlled loop is used when checking of test condition is mandatory after executing.
The components of an exit-controlled loop include:
- Initialization: This step involves initializing any loop control variables or other necessary variables before entering the loop.
- Loop Body: The loop body contains the main logic that is executed repeatedly as long as the loop condition remains true. It represents the set of statements or code that are executed within each iteration of the loop.
- Loop Condition: The loop condition is an expression that is evaluated at the end of each iteration. If the condition evaluates to true, the loop continues; if it evaluates to false, the loop terminates, and control moves to the next statement after the loop.
- Loop Execution: The loop execution is the process of running the loop body repeatedly as long as the loop condition remains true.
- Iteration: Each execution of the loop body is called an iteration. The loop body is executed repeatedly until the loop condition becomes false.
- Update: After each iteration, loop control variables (if any) may need to be updated to eventually make the loop condition false. This step ensures progress towards the exit condition.
- Exit Point: The loop condition is evaluated after each iteration. When the loop condition evaluates to false, the control flow exits the loop, and the program continues with the next statement after the loop.
Between Entry Controlled And Exit Controlled Loop In Tabular Form
|BASIS OF COMPARISON||ENTRY CONTROLLED LOOP||EXIT CONTROLLED LOOP|
|Description||Entry controlled loop is a loop in which the test condition is checked first, and then loop body will be executed.||Exit controlled loop is a loop in which the loop body is executed first and then the given condition is checked afterwards.|
|False Test Condition||If the test condition is false, loop body will not be executed.||If the test condition is false, loop body will be executed at least once.|
|Example||Examples of exit controlled loop include, For Loop and While Loop.||An example of exit controlled loop is Do While Loop.|
|Use||Entry controlled loop are used when checking of test condition is mandatory before executing loop body.||Entry controlled loop is used when checking of test condition is mandatory after executing.|
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