 The user must still enter every base letter in the word.The VNI Encoding uses up to two bytes to represent one Vietnamese vowel character, with the second byte supplying additional diacritical marks, therefore removing the need to replace control characters with Vietnamese characters, a problematic system found in TCVN1 (VSCII-1) and in VISCII, or using two different fonts such as is sometimes employed for TCVN3 (VSCII-3), one containing lowercase characters and the other uppercase characters.A similar approach is taken by Windows-1258 and VSCII-2.