Unfortunately, you are often going to see both At&t and Intel syntax to represent assembly instructions, so you will have to be comfortable with both. Some tools—such as GDB and objdump—use At&t syntax as the default while others—e.g., IDA and PEDA—use Intel syntax.
Here are some of the major differences with examples:
ATT Intel
different order of operands src, dst dst, src
no reg. prefix in Intel %rbx rbx
no size suffix in Intel movq mov
different location descriptions (%rbx) QWORD PTR [rbx]
no prefix for immediate in Intel $0x1F 0x1F
The language for sizes is also confusing. This chart is for x86-64. Pointers
(char *) are only 4 bytes in x86-32.
C Intel ATT Suffix Size (bytes)
char byte b 1
short word w 2
int dbl word l 4
long quad word q 8
char\* quad word q 8
float single precision s 4
double double precision l 8