A character representing a digit, n, is stored as an 8-bit ASCII code. It needs to be converted into an 8 bit sign-magnitude representation for the negative numerical value, -n. What is the algorithm for doing this?

Here is a step-by-step algorithm to convert an 8-bit ASCII code into an 8-bit sign-magnitude representation for the negative numerical value, -n:

1. Start with the 8-bit ASCII code for the digit n. ASCII codes for digits 0-9 are represented as 48-57 in decimal or 0011 0000 - 0011 1001 in binary.

2. Subtract the ASCII value of '0' (48 in decimal or 0011 0000 in binary) from the ASCII code to get the numerical value of the digit. This can be done by XORing the ASCII code with 0011 0000.

3. Now you have the binary representation of the digit. To represent it as a negative number in sign-magnitude form, simply set the most significant bit (MSB) to 1. This can be done by ORing the result with 1000 0000.

4. The result is the 8-bit sign-magnitude representation of -n.

Please note that this algorithm assumes that the input is a valid ASCII code for a digit. If the input is not a valid ASCII code for a digit, the result will not be meaningful.