Both the Ugaritic "alphabet" and the Phoenician "alphabet" must have been derived from an earlier abjad, from which we do not have any preserved example.
The earlier, unknown, abjad, must have been used to write the same 27 consonants as in the Ugaritic alphabet, but using graphic signs similar to those used by the 22-sign Phoenician alphabet, which resemble in form the Egyptian signs.
There is no doubt that the Egyptian writing system was the inspiration for the first abjad, because both the method of writing only the consonants and the direction of writing were inherited from the Egyptians.
In Ugarit, in order to write on earth tablets, like in Mesopotamia, the original graphic signs used for the 27 consonants were replaced with cuneiform signs.
On the other hand, the Phoenicians deleted 5 letters, because their language was simplified and the 5 deleted consonants were eventually pronounced identically with other 5 consonants. It is supposed that the Phoenician pronunciation was simplified so much because it was used as a lingua franca for commerce, by many people.
This reduction in the number of consonants created later problems for other Semitic people, e.g. Hebrews and Arabs, who still pronounced distinctly some of the consonants that were deleted from the Phoenician alphabet, so they had to invent diacritics to mark the missing consonants (e.g. shin and sin in Hebrew).
The earlier, unknown, abjad, must have been used to write the same 27 consonants as in the Ugaritic alphabet, but using graphic signs similar to those used by the 22-sign Phoenician alphabet, which resemble in form the Egyptian signs.
There is no doubt that the Egyptian writing system was the inspiration for the first abjad, because both the method of writing only the consonants and the direction of writing were inherited from the Egyptians.
In Ugarit, in order to write on earth tablets, like in Mesopotamia, the original graphic signs used for the 27 consonants were replaced with cuneiform signs.
On the other hand, the Phoenicians deleted 5 letters, because their language was simplified and the 5 deleted consonants were eventually pronounced identically with other 5 consonants. It is supposed that the Phoenician pronunciation was simplified so much because it was used as a lingua franca for commerce, by many people.
This reduction in the number of consonants created later problems for other Semitic people, e.g. Hebrews and Arabs, who still pronounced distinctly some of the consonants that were deleted from the Phoenician alphabet, so they had to invent diacritics to mark the missing consonants (e.g. shin and sin in Hebrew).