Addresses in Memory

An address is a 32-bit pattern, and any 32-bit word of main storage can hold it. For example, here is a fragment of a program:

          .text
sub1:     li       $v0,4                # service code 4, print string
          la       $a0,messH            # address of string to print
          syscall                       # invoke the service
          jr       $ra                  # return to caller
          .data
messH:    .asciiz  "Hello "

          .text
sub2:     li       $v0,4                # service code 4, print string
          la       $a0,messW            # address of string to print
          syscall                       # invoke the service
          jr       $ra                  # return to caller
          .data
messW:    .asciiz  "World\n"

          .data
sub1add:  .word sub1                    # address of the first subroutine
sub2add:  .word sub2                    # address of the second subroutine

The symbolic address sub1 stands for whatever 32-bit address the first byte of the first subroutine gets loaded into at run time.

In the .data section at the end of the program, the address represented by sub1 is stored in memory, at the symbolic address sub1add.

Part of the job of the assembler and the loader is to determine where in memory various parts of a program go. In source code, you use symbolic addresses for these locations.

The source code interleaves text and data, but the assembler and loader will put all machine code into the text section of memory and all data into the data section of memory.

QUESTION 2:

If the address of sub1 is 0x00400000, what bit pattern do you expect to see in memory at the location sub1add?

Answer:

Addresses in Memory

QUESTION 2: