The first Persian Empire of the Achaemenid dynasty rose to power in the middle of the 6th century BCE and quickly conquered an area that stretched from Mesopotamia to Afghanistan. Early in the history of the dynasty, a syllabic script to write the Old Persian language was developed. This script was not a direct descendent of the Sumerian and Akkadian systems, because even though the physical appearance of Old Persian signs are Cuneiform, or in the shape of wedges, the actual shape of the signs do not correspond to signs in older systems with similar phonetic values. Old Persian only kept the cuneiform appearance of its characters simply out of tradition, and the actual shape of the signs were completely original.
The Old Persian "syllabary" is somewhat of a misnomer, in that it also contains some logograms. However, since the majority of signs are syllabograms, Old Persian is classified as a syllabic script. It is also a very skeletal syllabary, in that sounds like /pu/ do not have independent signs but instead must be written with the signs pa and u. Also, single consonant that form part of a consonant cluster or the end of a syllable are also written with syllabograms with the /a/ vowel. So, in such cases, the syllabogram that contains the vowel /a/ drop its vowel value and in effect becomes a consonant.
Note that the symbol /ç/ is the traditional transcription of the sound [̣s], or apico-palatal voiceless fricative, much like /ch/ in German "ich".
These are the logograms used in Old Persian:
And these are numbers in Old Persian:
Also, a slanted vertical wedge is used as the separator between words, as illustrated in the following example:
The example translates as "I, Cyrus the king, an Achaemenid". The word separators are in purple. Syllabograms that are used only for their consonantal values have their vowels placed between parentheses, such as in the sign sequence r(i)-u that writes out the sound /ru/, and in the ending consonant /m/ in adam.