第四週 Chp:4 系統單元的組成元件

ROM (Read-only memory)

Read-only memory (ROM) is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware (software that is very closely tied to specific hardware, and unlikely to need frequent updates) 
只讀存儲器（ROM）是一類計算機及其他電子設備中使用的存儲介質。 ROM中存儲的數據不能被修改，或可以進行修改，只能緩慢或困難，所以它主要用於分發是非常密切的依賴特定的硬件，並不太需要頻繁更新固件（軟件）



RAM (Random access memory) 

Random access memory (RAM) is a form of computer data storage. Today, it takes the form of integrated circuits that allow stored data to be accessed in any order with a worst case performance of constant time. Strictly speaking, modern types of DRAM are therefore not random access, as data is read in bursts, although the name DRAM / RAM has stuck. However, many types of SRAM, ROM, OTP, and NOR flash are still random access even in a strict sense. RAM is often associated with volatile types of memory (such as DRAM memory modules), where its stored information is lost if the power is removed. Many other types of non-volatile memory are RAM as well, including most types of ROM and a type of flash memory called NOR-Flash. The first RAM modules to come into the market were created in 1951 and were sold until the late 1960s and early 1970s.
隨機存取存儲器（RAM）是計算機數據存儲的一種形式。今天，它需要的集成電路，允許以任何順序訪問一個常數時間的最糟糕的情況下的性能存儲數據的形式。因此，嚴格說來，現代的DRAM類型是不是隨機存取，突發讀取數據，雖然名字DRAM/內存卡。然而，許多類型的SRAM，ROM，OTP的，和NOR閃存仍然是，即使在嚴格意義上的隨機存取。 RAM通常是與揮發性類型的存儲器（如DRAM內存模塊），其存儲的信息丟失，如果電源被移走。許多其他類型的非易失性內存的RAM，以及包括大多數類型的ROM和NOR閃存的閃存類型。進入市場的第一個RAM模塊，創建於1951年，直到60年代後期和70年代初出售。