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Array iteration refers to the process of going through each element present in an array one by one. In programming, arrays are used to store multiple values in a single variable, so it's often necessary to access each element individually, whether to perform calculations or for other manipulations.

Imagine you have a list of numbers, like a shopping list with prices for each item. To calculate the total price, you would look at each item's price and add it up. Similarly, with array iteration in a program, we systematically access each 'item' (element) and can perform operations such as summing their values.

To iterate through an array in programming, we typically use a 'for' loop, which goes through the array from the first element (at index 0) to the last element. Here's a simple visualization using pseudocode:

• for each 'element' in 'array':
  perform 'action' on 'element'

This template is the backbone of how you'll often see array iteration carried out in actual code.

A sum variable is like a bucket where we collect drops of water one by one, and by the end, we can see how much water the bucket holds. In the context of programming, the sum variable is used to keep a running total. When calculating the sum of an array, each element's value is added to this total one at a time.

In the example provided, the sum variable is initialized to 0 and then gets incremented with each value from the array.

Here's a breakdown:

• Initialize the sum variable with 0: This is like starting with an empty bucket.
  int sum = 0;
• With each iteration of the loop, add the current element's value to the sum:
  sum += array[i];which is the same as sum = sum + array[i];
  This is like adding water for each item's price to our bucket.

By the end of the loop, the sum variable will hold the total value of all elements in the array, giving us the total we sought after.

A 'for' loop in programming is a control flow statement for specifying iteration, which allows code to be executed repeatedly. Think of it like a loop in a roller coaster: you go in, around, and back to the start, only exiting after a set number of loops or until a condition is met.

In the example provided for summing array elements, the 'for' loop repeats actions within its block for each element in the array until it reaches the end. Here's the structure of a 'for' loop:

• Initialization: Set the starting point (e.g., int i = 0;). The loop counter 'i' starts at zero, which corresponds to the first element in an array, as arrays are zero-indexed — meaning they begin counting from zero.
• Condition: Define the end point (e.g., i < array.length;). The loop will run as long as this condition holds true.
• Increment: Update the loop counter after each iteration (e.g., i++; which is short for i = i + 1;), effectively moving to the next element in the array.
• Body: The actual code to execute, such as adding the array's current element to the sum variable.

Using the 'for' loop is a fundamental concept and one of the most common ways to perform array iteration to execute repeated actions, like calculating a sum.