Introduction:
A shift register is a type of digital circuit that is used to store and transfer data. It consists of a series of flip-flops connected in cascade, where each flip-flop stores one bit of data. The data can be input or output in a serial or parallel manner. In this question, we are asked to identify the characteristic that is not associated with a shift register.

Characteristics of a shift register:
1. Serial in/parallel out: This characteristic allows data to be inputted one bit at a time in a serial manner and outputted all at once in parallel. It is commonly used for applications such as data storage and data transfer between devices.

2. Parallel in/serial out: This characteristic allows data to be inputted all at once in parallel and outputted one bit at a time in a serial manner. It is commonly used for applications such as data transmission and signal conversion.

3. Parallel in/parallel out: This characteristic allows data to be inputted and outputted all at once in parallel. It is commonly used for applications such as data processing and data manipulation.

4. Serial in/parallel in: This characteristic is not associated with a shift register. It does not make sense to have both serial input and parallel input in a single shift register. The input method should be either serial or parallel, but not both simultaneously.

Conclusion:
In summary, the correct answer to the given question is option 'A' - Serial in/parallel in. This characteristic is not associated with a shift register because it does not make sense to have both serial input and parallel input in a single shift register. The other three characteristics - serial in/parallel out, parallel in/serial out, and parallel in/parallel out - are all commonly found in shift registers and serve different purposes in digital circuit design.