mov r0,r1 // move data from r1 to r0

mov r0,99 // load r0 with 99 (only certain immediate values are possible)

str r0,[r1,0] // store register r0 to address pointed to by (r1 + (0 * ''size'')) where ''size'' is 8 bytes for 64-bit stores

strb w0,[r1,0] // like str but writes one byte only - note the use of w0 for the source register name