The rupiah (symbol: Rp; currency code: IDR) is the official currency of Indonesia, issued and controlled by Bank Indonesia. Its name is derived from the Sanskrit word for silver, rupyakam (रूप्यकम्). Sometimes, Indonesians also informally use the word perak ('silver' in Indonesian) in referring to rupiah in coins. The rupiah is divided into 100 cents (Indonesian: sen), although high inflation has rendered all coins and banknotes denominated in cents obsolete. The rupiah was introduced in 1946 by Indonesian nationalists fighting for independence. It replaced the Japanese-issued version of the Netherlands Indies gulden which had been introduced during the Japanese occupation in World War II. In its early years, the rupiah was used in conjunction with other currencies, including a new version of the gulden introduced by the Dutch. The Riau Islands and the Indonesian half of New Guinea (Irian Barat) had their own variants of the rupiah in the past, but these were subsumed into the national rupiah in 1964 and 1971, respectively (see Riau rupiah and West Irian rupiah).