Hello and welcome to a new section.
In this section, we are going to study the carry flag, the overflow flag, sign flag, and zero flag in
x64 assembly programming.
These flags are shown in this part of the windows here in x64dbg.
The carry flag is over here,
-. The overflow flag is over here, -. The sign
flag is here, -. The zero flag is over here, -. The others are not so important.
So the carry flag is primarily used in arithmetic operations.
It is set when there is an overflow out of the most significant bit for unsigned operations, indicating
that the result was too large to fit in the register.
For example, in an addition operation, if the sum of two numbers exceeds the maximum value that can
be stored in the destination operand, the - is set.
It's also used in multi-precision arithmetic operations.
The overflow flag is set when the signed arithmetic operation results in a value too large or too small
to be represented in the destination operand.
This occurs when there is an overflow or underflow out of the range of representable values for signed
numbers.
For instance, adding two large positive signed integers might result in a negative value if an overflow
occurs, in which case the - would be set.
The sign flag indicates the sign of the result of an arithmetic or logical operation.
It is set if the result is negative,
that is, the most significant bit of the result is one in two's complement representation.
The - is also used in conjunction with the - to determine overflow in subtraction and comparison operations.
The zero flag is set if the result of an arithmetic or logical operation is zero.
This flag is often used for equality checks in conditional branch instructions.
For example, after a subtract operation, if the - flag is set, it indicates that the two operands
were equal.
These flags are part of the processor status registers and are automatically set or cleared by the
CPU based on the results of various operations.
They play a crucial role in decision-making and controlling the flow of a program.
All this will become clear in the following sections that we are going to cover next.
So that's all for this video.
Thank you for watching.