Consider the following 8-bit signed integers x, y using sign-magnitude format is x = 10110100, y = 01001100. Which of the following operations results overflow?

The correct option is x - y.

To determine which operation results in an overflow, we first need to find the decimal values of the 8-bit sign-magnitude integers $x$ and $y$.
In an 8-bit sign-magnitude representation:
- The most significant bit (MSB, leftmost bit) represents the sign: 0 for positive (+) and 1 for negative (-).
- The remaining 7 bits represent the magnitude (absolute value) of the number.
- The range of values that can be represented is from $-(2^7-1)$ to $+(2^7-1)$, which is $[-127,+127]$.

1. Convert $x=10110100$ to decimal:
- Sign bit (MSB) = 1 (negative)
- Magnitude bits = ${0110100}_2=2^5+2^4+2^2=32+16+4=52$
- Therefore, $x=-52$

2. Convert $y=01001100$ to decimal:
- Sign bit (MSB) = 0 (positive)
- Magnitude bits = ${1001100}_2=2^6+2^3+2^2=64+8+4=76$
- Therefore, $y=+76$

3. Evaluate the operation $x-y$:

$x-y=-52-76=-128$

Since the minimum representable value in 8-bit sign-magnitude format is -127, the result of -128 lies outside the allowed range of $[-127,+127]$. Thus, the operation x - y results in an overflow.