.text
                .global _start

// 1. calculate the maximum
// 2. calculate the minimum
// 3. calculate max - min
// 4. bit-right-shift twice

// R0 := maximum
// R1 := minimum
// R2 := the number of items left to iterate through
// R3 := the address of the current number in the list (pointer)
// R4 := the actual number pointed to by R3

_start:
            LDR     R2, N       // set R2 to length of list
            LDR     R3, =NUMBERS // pont R3 to first element in list
            LDR     R0, [R3]    // set max and min as the first element
            LDR     R1, [R3]

MINMAX:     SUBS    R2, R2, #1  // decrement N by 1
            BEQ     CALCSTDEV   // if N = 0 then GOTO CALCSTDEV
            ADD     R3, R3, #4  // else move pointer to next number
            LDR     R4, [R3]    // load the number into R4
            CMP     r4, r0      // compare with current max
            MOVGT   R0, R4      // if R4 > R0 then max = R4
            CMP     R4, R1      // compare with current min
            MOVLT   R1, R4      // if R4 < R0 then min = R4
            B       MINMAX

CALCSTDEV:  SUB     R3, R0, R1  // R3 := MAX - MIN
            MOV     R3, R3, ASR #2
            STR     R3, =STDEV

STDEV:      .word   0   // final result
N:          .word   10  // length of data list
NUMBERS:    .word   4, 5, 3, 27, 1, 18, 2, 6, 10, 23    // list of data