Question

Consider the following code:

static int array[30]
int x = array[25]

What is the equivalent in assembler, given array is defined in .data?

Answer 1

In assembly language, accessing an element from a static array involves calculating the offset by multiplying the index by the size of each element and then loading the value from the memory address into a register. The example provided shows accessing the 26th element of an array in x86 assembly language, assuming integer sizes are standard 32 bits (4 bytes).

Step-by-step explanation:

In assembly language, accessing an element of an array involves calculating the offset of that element from the base of the array and then loading the value from the calculated address into a register. Since the array is defined in the .data section, we'll have a label for the beginning of the array. To access the 26th element (array indices start at 0), we have to consider the size of each array element. Assuming a standard 32-bit integer size (4 bytes), we would calculate the address by multiplying the element index (25) by the number of bytes per element (4).

Here's an example in x86 assembly:

.data
array dd 30 dup(0) ; Array of 30 integers

.code
mov eax, [array + 25 * 4] ; Move 26th element into EAX register

In this code, we're using the base+offset addressing mode where 'array' is the base label and '25 * 4' is the offset for the 26th element. 'dd' defines a double word, which is 32 bits or 4 bytes, suitable for integers.