gdb <program> [ core ]			: to start gdb
(gdb) list [ <line1> ] [ <line2> ]	: to see source codes
(gdb) list <function name>		:
(gdb) run [ <args> ]			: to exec "<program> <args>" in gdb
(gdb) backtrace				: to trace the error
(gdb) break <line no>			: to set break point at line <line no>
(gdb) break <function name>		:
(gdb) break <line no>/<function name> if <condition>
(gdb) continue				: to continue
(gdb) whatis <variable name>		: to see the type of a variable
(gdb) print <variable name>		: to see its value
(gdb) step				: to go a step forward
(gdb) info line <line no of src>	: to see the machine lang code info
(gdb) disassemble <from> <to>		: to disassemble the machine lang codes