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79 lines
1.4 KiB
Markdown
79 lines
1.4 KiB
Markdown
---
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title: While-loop
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---
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A while loop statement repeatedly executes a target statement as long as a given condition is true. It is often used when the number of iterations is unknown.
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Syntax:
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```cpp
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while(condition) {
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statement(s);
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}
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```
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A key point of the while loop is that the loop might not ever run.
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When the condition is tested and the result is false, the loop body will be skipped and the first statement after the while loop will be executed.
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Another important point about the while loop is to remember to increment/decrement/modify the variable used for checking the given condition at the beginning of each iteration, at the end of your loop, otherwise the loop will enter into an infinite loop.
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Example:
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```cpp
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#include <iostream>
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using namespace std;
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int main () {
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// Local variable declaration:
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int a = 10;
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// while loop execution
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while( a < 20 ) {
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cout << "value of a: " << a << endl;
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a++;
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}
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return 0;
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}
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```
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Output:
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```
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value of a: 10
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value of a: 11
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value of a: 12
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value of a: 13
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value of a: 14
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value of a: 15
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value of a: 16
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value of a: 17
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value of a: 18
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value of a: 19
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```
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Example of Skipped Loop Body:
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```cpp
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#include<iostream>
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using namespace std;
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int main(){
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//Local variable declaration
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int age=10;
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//while loop execution
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while(age>21) {
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cout<<"The citizen is an adult."<<endl;
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}
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return 0;
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}
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```
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Output:
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```
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```
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### Sources
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* www.tutorialspoint.com
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