Explanation:

In the context of computer input and output, "input" refers to the act of providing data or instructions to the computer. Option (c) "data or information that has been entered into the computer" directly defines this, as it is the content that has been supplied. Option (d) "the transmission of data that has been input into the computer" describes the process by which this data moves into the system. Both aspects are integral to the concept of input. Option (a) describes processing, not just input. Option (b) describes retrieval, which is related to output or access, not the initial input. Therefore, option (e) "Both (c) and (d) above" provides the most comprehensive definition of input in this context.