Final answer:
The left side of a 2x4 K-Map typically lists binary combinations for two variables, generally Y and X, in either binary or Gray code sequence, unless otherwise specified in the context.
Step-by-step explanation:
The order of inputs on the left side of a 2 column x 4 row K-Map (Karnaugh Map) with inputs X, Y, and Z is determined by the binary values that these variables can take. For a K-Map that visualizes three variables, typically the left side of the map will list the binary combinations for two of the variables, while the top or bottom row will list the binary combinations for the remaining variable.
In most cases, the variable Z will not be on the left side since it is common to have the two variables with more possible combinations on the left. Therefore, if we follow the logical sequence from 00 to 11 (0 to 3 in decimal), the left side would usually be represented by the Y and X variables, starting with '00' at the top and ending with '11' at the bottom, or it could also be in Gray code order where adjacent rows only differ by one bit. However, the precise order can change depending on additional constraints provided by the context or problem requirements.