CODEWITHSUNDEEP
cmemorygdb
David
David

Reputation: 1

How many bytes of data can be stored in a single memory address

I have learned that a memory is just a collection of bytes storage that are numbered with address thus I have reached the conclusion that each memory address can stores just one byte of data.

I am currently learning how to use the gdb debugger to examine memory but I'm confused as to how the x command of gdb is used. I have also learned that a number can be prepended to the format of x command to examine multiple units at the target address and also the default size of a single unit is 4 bytes.

How is it possible that a 4-byte data can be stored at a memory address that can hold only one byte? and also how is it possible that x/8xb also works at a given memory address when the whole data can be displayed using only a word (i.e x/1w)?

Upvotes: 0

Views: 1406

Answers (1)

ikegami
ikegami

Reputation: 385955

The minimal addressable memory is often 8 bits, but it's not always the case. For example, I worked on a system with 32,768 addresses of 16-bit values.

How is it possible that a 4-byte data can be stored at a memory address

They're not. The address is the address of the first byte.

0x11223344 at address 0x1000 on a little-endian system which can address 8-bit values:

       +--------+
0x1000 |  0x44  |
       +--------+
0x1001 |  0x33  |
       +--------+
0x1002 |  0x22  |
       +--------+
0x1003 |  0x11  |
       +--------+

0x11223344 at address 0x1000 on a big-endian system which can address 8-bit values:

       +--------+
0x1000 |  0x11  |
       +--------+
0x1001 |  0x22  |
       +--------+
0x1002 |  0x33  |
       +--------+
0x1003 |  0x44  |
       +--------+

Upvotes: 2

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