How To Update A Variable Outside A While Loop C

In calculator programming, loops are used to repeat a block of lawmaking.

For instance, permit's say we desire to show a message 100 times. So instead of writing the print statement 100 times, we can use a loop.

That was just a simple case; we tin can achieve much more efficiency and sophistication in our programs past making effective use of loops.

There are 3 types of loops in C++.

for loop
while loop
do...while loop

This tutorial focuses on C++ for loop. Nosotros will learn about the other type of loops in the upcoming tutorials.

C++ for loop

The syntax of for-loop is:

          for (initialization; condition; update) {     // body of-loop  }

Hither,

initialization - initializes variables and is executed only in one case
condition - if true, the torso of for loop is executed
if fake, the for loop is terminated
update - updates the value of initialized variables and over again checks the condition

To learn more about conditions, bank check out our tutorial on C++ Relational and Logical Operators.

Flowchart of for Loop in C++

C++ for loop flowchart — Flowchart of for loop in C++

Example one: Printing Numbers From i to v

          #include <iostream>  using namespace std;  int chief() {         for (int i = 1; i <= v; ++i) {         cout << i << " ";     }     render 0; }

Output

          1 2 3 4 5

Here is how this plan works

Iteration	Variable	i <= 5	Action
1st	`i = 1`	`true`	`i` is printed. `i` is increased to `ii`.
2nd	`i = 2`	`true`	`2` is printed. `i` is increased to `3`.
third	`i = 3`	`true`	`three` is printed. `i` is increased to `4`.
4th	`i = 4`	`truthful`	`four` is printed. `i` is increased to `5`.
5th	`i = v`	`true`	`5` is printed. `i` is increased to `six`.
6th	`i = 6`	`simulated`	The loop is terminated

Case 2: Display a text 5 times

          // C++ Plan to display a text 5 times  #include <iostream>  using namespace std;  int chief() {     for (int i = 1; i <= 5; ++i) {         cout <<  "Howdy World! " << endl;     }     return 0; }

Output

          Hullo World! Hello Globe! Hello World! Howdy Globe! Hello Globe!

Here is how this program works

Iteration	Variable	i <= 5	Action
1st	`i = ane`	`true`	`Hello Earth!` is printed and `i` is increased to `ii`.
2nd	`i = 2`	`truthful`	`Hello World!` is printed and `i` is increased to `3`.
3rd	`i = three`	`true`	`Hello World!` is printed and `i` is increased to `4`.
4th	`i = iv`	`true`	`Hello World!` is printed and `i` is increased to `5`.
5th	`i = 5`	`true`	`Howdy World!` is printed and `i` is increased to `6`.
6th	`i = 6`	`false`	The loop is terminated

Case iii: Find the sum of first n Natural Numbers

          // C++ programme to notice the sum of offset due north natural numbers // positive integers such as 1,2,3,...n are known as natural numbers  #include <iostream>  using namespace std;  int main() {     int num, sum;     sum = 0;      cout << "Enter a positive integer: ";     cin >> num;      for (int i = 1; i <= num; ++i) {         sum += i;     }      cout << "Sum = " << sum << endl;      return 0; }

Output

          Enter a positive integer: 10 Sum = 55

In the above example, nosotros have two variables num and sum. The sum variable is assigned with 0 and the num variable is assigned with the value provided by the user.

Annotation that nosotros have used a for loop.

          for(int i = 1; i <= num; ++i)

Here,

int i = i: initializes the i variable
i <= num: runs the loop as long as i is less than or equal to num
++i: increases the i variable by 1 in each iteration

When i becomes 11, the status is false and sum will be equal to 0 + 1 + 2 + ... + 10.

Ranged Based for Loop

In C++eleven, a new range-based for loop was introduced to work with collections such as arrays and vectors. Its syntax is:

          for (variable : collection) {     // body of loop }

Here, for every value in the drove, the for loop is executed and the value is assigned to the variable.

Instance 4: Range Based for Loop

          #include <iostream>  using namespace std;  int principal() {        int num_array[] = {1, 2, 3, 4, 5, 6, vii, viii, 9, 10};        for (int northward : num_array) {         cout << due north << " ";     }        render 0; }

Output

          1 2 3 four 5 vi 7 8 9 ten

In the above program, we have declared and initialized an int array named num_array. It has 10 items.

Here, we accept used a range-based for loop to access all the items in the array.

C++ Space for loop

If the status in a for loop is ever true, it runs forever (until memory is full). For instance,

          // infinite for loop for(int i = 1; i > 0; i++) {     // cake of lawmaking }

In the above programme, the status is always true which volition then run the code for space times.

Check out these examples to learn more:

C++ Plan to Calculate Sum of Natural Numbers
C++ Program to Find Factorial
C++ Program to Generate Multiplication Table

In the next tutorial, we will learn about while and practice...while loop.