• Scripts were developed to extend man’s scope and range.
  
  
• Pictograms: purely pictorial symbols.
  
  
• Pictograms were used to represent the concepts (ideograms) or words (logograms) they represented.
  
  
• Ultimately, logograms develop into phonograms, in which the sound value (phoneme) of mono-syllabic words is attached to the symbols representing these words.
  
  
• Finally the syllabic script develops into an alphabetic script in which symbols represent single phonemes instead of syllables.

Universal sequence from purely pictorial representation (pictograms) to sets of abstracted sound-representing symbols (phonograms).
Pictograms convey meaning without intervention of sound values; there may be a symbol meaning ‘town’, ‘river’ or ‘mountain’ irrespective of what the word for ‘town’, ‘river’ or ‘mountain’ sounds like, and thus regardless of any specific language. Such a symbol is named a logogram (pictogram for a specific word). The advantage of logograms is their universal applicability – because they are language-independent – but they have the obvious disadvantage that there must be a separate symbol for every word.

All complete writing systems the world has ever known, do effectively contain both logograms and phonograms. As purely pictorial ‘proto-scripts’ develop into ‘scripts’ or writing systems, naturally drawn pictograms are stylised and augmented with drawings for abstract phenomena (hence called ideograms), and will ultimately contain logograms for all basic words of a specific language. Phonograms are developed out of logograms through a process starting with the rebus principle: the sound values (in a specific language!) of mono-syllabic words are attached to the logograms representing these words, thus creating a phonetic syllabary or syllabic script.