Registers

Question 1

ARM has sixteen registers visible at any one time. They are named R0 to R15. All are 32 bits wide.

Question 2

The registers may also be referred to by the following aliases:

Question 3

All of the registers are general purpose, save for:

Question 4

All of the registers are general purpose, save for:
R14 / LR

Answer 4

the link register which holds the callers’s return address.

Question 5

All of the registers are general purpose, save for:
R15 / PC

Answer 5

which holds the program counter.

Question 6

In addition to the main registers there is also a status register:

Answer 6

CPSR is the current program status register. This holds flags: results of arithmetic and logical operations.

Question 7

Strictly R13 is used for the ____ _______ by convention, rather than a rule, in ARM mode. In Thumb mode it is more hardwired.

Answer 7

Strictly R13 is used for the stack pointer by convention, rather than a rule, in ARM mode. In Thumb mode it is more hardwired.

Question 8

ARM is a load-store architecture:

Answer 8

• You must load values into registers in order to operate upon them.
• No instructions directly operate on values in memory.