On a CICS 3270 style terminal, what is the difference between the Enter key, PF keys, and PA keys when they send input attention to a CICS transaction?

Introduction / Context:
CICS traditionally interacts with users through 3270 type terminals or emulators that support different attention keys. The Enter key, PF keys, and PA keys each send specific signals to CICS, and understanding how they differ is important when you design BMS maps and transaction flows. This question focuses on the way these keys transmit data and attention identifiers to a CICS program.

Given Data / Assumptions:

• The terminal supports an attention identifier, often called an AID, associated with keys like Enter, PF, and PA.
• User input is entered into fields on a BMS map and may be marked as modified.
• CICS receives both attention identifiers and, in many cases, modified data from the terminal.
• The question asks how Enter, PF, and PA keys differ in what they transmit.

Concept / Approach:
When a user presses the Enter key on a 3270 screen, the terminal sends an attention identifier that represents the Enter action and also sends the modified data fields back to CICS. PF keys, or Program Function keys, similarly send an attention identifier that indicates which PF key was pressed, and they also transmit modified screen data so that applications can process user input and the selected function together. PA keys, or Program Attention keys, differ because they send only an attention identifier without sending modified data, making them suitable for actions that do not depend on updated field content.

Step-by-Step Solution:
Step 1: Associate the Enter key with sending both the AID and modified data fields from the current screen. Step 2: Associate PF keys with programmed functions that also send both the AID and the current modified screen data. Step 3: Associate PA keys with sending only an AID indicator and no modified data fields from the screen buffer. Step 4: Select the option that clearly describes these three behaviors and highlights that PA keys do not send data fields.

Verification / Alternative check:
CICS terminal and BMS documentation explains that Enter and PF keys are treated similarly with respect to data transmission, while PA keys are often described as non data keys. Sample mapping diagrams show that PA keys can trigger attention for functions such as help or cancel without needing field updates. This matches the explanation given in the correct option and contradicts the alternatives that interchange or misuse the roles of these keys.

Why Other Options Are Wrong:
Option B reverses the behavior of PF and PA keys by claiming PF keys send only an AID and PA keys send full data, which is incorrect. Option C invents uses such as powering the terminal and resetting the region, which are not tied to these keys. Option D is wrong because Enter and PA keys are not identical and generate different AID codes. Option E incorrectly associates the keys with user roles and security policy rather than their technical function on the terminal.

Common Pitfalls:
A common pitfall is relying on PA keys for operations that actually require updated user data, which leads to missing input on the program side. Another mistake is not checking the EIBAID field properly to distinguish Enter from PF and PA keys, causing incorrect branch logic. Designers sometimes overload PF keys with too many functions without clear labeling, confusing users. Understanding exactly how Enter, PF, and PA keys behave at the data transmission level helps you map keys to appropriate actions and handle input correctly in CICS programs.

Final Answer:
The Enter key sends modified data fields plus an attention identifier, PF keys send both the AID and screen data for programmed function selection, while PA keys send only the AID without transmitting modified data fields