Declaring Pointers for Different Addressing Types

Pointers revisited

The pointer is a memory cell or a register that contains the address of another memory cell. Memory pointers have their own addresses because they are memory cells too. On a 32-bit Linux, pointers are 32-bit, and on a 64-bit Linux, pointers are 64-bit.

Addressing types

Memory cells can be of one byte, half word, word, or double word sizes. Therefore, we can have a pointer to a byte, a pointer to a half word, a pointer to a word, and a pointer to a double word. If we want to load or store, we would use the following:

• Byte: We use LDRB/STRB instructions and w-registers for storing the data.

• Half word: We use LDRH/STRH instructions and w-registers for storing the data.

• Word: We use LDR/STR instructions and w-registers for storing the data.

• Double word: We use LDR/STR instructions and x-registers for storing the data.

We always use x-registers for memory addresses. Here are some illustrated examples: