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I have come upon x86 assembly code I don't understand and can't find anything about it. The bit of code i don't understand is parentheses around register ecx: movb (%ecx),%al. What does this code mean? I am familiar with registers and instructions, but have never come upon this.

I was trying to find something about it in videos and guides, but did not find anything.

Looks something like this in context

pushl %ebp 
movl %esp,%ebp 
movl 8(%ebp),%ecx 
...
movb (%ecx),%al  #<-- the code i am wondering about
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Jackson Shaw
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1 Answers1

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The syntax (%reg) is the AT&T assembler syntax for dereferencing the content of a register as an address. It's equivalent to the Intel syntax [reg].

What you have there is the value in the partial register %al being written into the byte pointed to by the address in %ecx.

Govind Parmar
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