Question E8D11:
What is one advantage of using ASCII code for data communications?  

Choices:  
A: It includes built-in error correction features  
B: It contains fewer information bits per character than any other code  
C: It is possible to transmit both uppercase and lowercase text  
D: It uses one character as a shift code to send numeric and special characters    

Correct Answer is  C: It is possible to transmit both uppercase and lowercase text  

Correct answer: C — It is possible to transmit both uppercase and lowercase text

Why this is correct:
- ASCII is a 7-bit code ($2^7 = 128$ characters) that includes separate codes for uppercase and lowercase letters. For example, $A = 65$ (0x41) and $a = 97$ (0x61).
- Lowercase and uppercase letters differ by $32$ ($2^5$), so toggling bit 5 changes case:
  $$\text{lowercase} = \text{uppercase} + 32$$

Why the other choices are incorrect:
- A: ASCII has no built-in error correction. At most, an optional parity bit provides simple error detection, not correction.
- B: ASCII uses 7 bits per character (often sent as 8 bits), which is more than some codes (e.g., 5-bit Baudot). It does not contain fewer bits than “any other code.”
- D: Using a shift code for numerics/specials is a feature of 5-bit Baudot (ITA2), not ASCII. ASCII assigns unique codes to digits and symbols without needing a shift.

Useful facts/rules:
- Standard ASCII: 7-bit, $2^7 = 128$ characters.
- Extended “8-bit ASCII” variants: $2^8 = 256$ characters.
- Case toggle rule: add or subtract $32$ to switch between uppercase and lowercase letters in ASCII.