Program code:

#Function 'decimalToHex' to convert a decimal number 
#into a hex number.
def decimalToHex(decimal):
    if decimal < 10:
        return str(decimal)  # Return the decimal value as a string if it is less than 10
    elif decimal == 10:
        return 'A'
    elif decimal == 11:
        return 'B'
    elif decimal == 12:
        return 'C'
    elif decimal == 13:
        return 'D'
    elif decimal == 14:
        return 'E'
    elif decimal == 15:
        return 'F'
    else:
        return None  # Return None for invalid inputs


# Prompt the user to enter a decimal value between 0 and 15
decimal = int(input("Enter a decimal value (0 to 15): "))

# Convert the decimal value to hex
hexValue = decimalToHex(decimal)

# Display the result
if hexValue is not None:
    print("The hex value is", hexValue)
else:
    print("Invalid input")

Executed Output 1:

Enter a decimal value (0 to 15): 11
The hex value is B

Executed Output 2:

Enter a decimal value (0 to 15): 5
The hex value is 5

Executed Output 3:

Enter a decimal value (0 to 15): 31
Invalid input