[Other] An Overview of Arrays and Memory

One integer takes 32bit in memory, 1 byte = 8bits, therefore one integer takes 4 bytes.

Now let's assume we have an array: [1,2,3]

4bytes . 4bytes . 4bytes

| . | . | . | . | . | . | . | . | . | . | . | . |

1 . 2 . 3

It tooks 4 * 3 bytes for three integers in an array. What if we want to add two more integers into the array, how the memory allocate?

A. it appends another 8 bytes in the end

B. it recreate an new array with 4 * 5 bytes size.

B. is the correct answer. It always create a new larger array and delete the old array. The simple reason for this is because we never know after array, it might have other code:

var a = [1,2,3]

var c = 4

4bytes . 4bytes . 4bytes 4bytes

| . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . |

1 . 2 . 3 . c=4

It assign 4 bytes to variable c in memory. We cannot simply append more memory after the old array.

巴特西

[Other] An Overview of Arrays and Memory

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