need to write an ARM assembly program which can be compiled

need to write an ARM assembly program which can be compiled by arm-elf-gcc to analyze the
content of register r0:
first give a value of r0(such as 100)
then– Register r1 holds the value of r0[7:0]
– Register r2 holds the value of r0[15:8]
– Register r3 holds the value of r0[30:18]
thx^_^

Solution

ARM code:

AREA Sample, CODE, READONLY

;code entry  

     ENTRY                  

;main                       

start

     MOV r0, #100                 ;move constant 100 into r0

     AND r1, r0, #0x000000ff      ;lower 8 bits

     AND r2, r0, #0x0000ff00      ;get r0[15:8]

     AND r3, r0, #0x7ffc0000      ;get r0[30:18]

     END