How to convert between uppercase and lowercase letters in ASCII

Case conversion rules in ASCII:

ASCII Value Ranges:

• Uppercase letters A-Z: 65-90
• Lowercase letters a-z: 97-122

Conversion Rules:

1. Uppercase to Lowercase: ASCII value + 32

   • Example: 'A' (65) → 'a' (97)
   • Formula: lower = upper + 32

2. Lowercase to Uppercase: ASCII value - 32

   • Example: 'a' (97) → 'A' (65)
   • Formula: upper = lower - 32

Bitwise Operation Method:

• Uppercase to Lowercase: lower = upper | 0x20 (set bit 5)
• Lowercase to Uppercase: upper = lower & 0xDF (clear bit 5)

Programming Example (Python):

python
# Uppercase to Lowercase
char = 'A'
lower_char = chr(ord(char) + 32)  # 'a'

# Lowercase to Uppercase
char = 'a'
upper_char = chr(ord(char) - 32)  # 'A'

# Bitwise operation method
lower_char = chr(ord('A') | 0x20)  # 'a'
upper_char = chr(ord('a') & 0xDF)  # 'A'

Important Notes:

• Verify character is a letter before conversion
• Non-letter characters should not be converted
• 32 is the fixed difference between uppercase and lowercase ASCII values