Letter Alif 
is the first letter of the Arabic
alphabet, The sound of letter Alif and Hamza 
is identical
Letter Alif is weak consonants,
as a long vowel letter, its function is to slightly lengthened the
corresponding short vowels
When a harkah or short vowel
signs
on or under letter Alif it is
not called Alif but Hamzah
If there is no vowel signs over Alif then is simply called Alif
The Holy Qur'an printed in sub-continent
Indo-Pakistan instead of printing Hamzah over
Alif (where a hamzah comes in the middle of a word and is shown riding an Alif
such as ) it is simply denoted by sukun sign and Hamzah is
pronounced. But in the copies of the Holy Qur'an printed in Egypt,
Turkey, Saudi Arabic and elsewhere a Hazah with a sukun is actually printed
over
Alif and this is in fact, is the correct script. example 
It should be understood that Alif is always Sakin and is never the first letter in a word. It always comes after another letter, whereas Hamzah may and generally does come as the first letter in a word.
Letter Hamza
hardly comes alone; it sits on the letter Alif , waw or Ya
When letter Alif which serves as a long vowel, comes at the end of a word, its is to be written YA unless it is the third letter in the word and is not converted from an original YA
A final Alif serving as a long vowel retains its shape only in one case; if it third component character to a word and is not regard as converted Alif from a original Ya as in (daaa) Otherwise the Alif is to be written Ya