顧名思義，只讀存儲器(只讀存儲器) cannot be written to. The contents of the memory are decided during the design process and data is programmed during the manufacturing process. As such, 只讀存儲器 is very cheap in terms of space and also has good timing and power characteristics. It is also non-volatile, retaining its contents indefinitely. It is often used for holding program parts which will not change during the life of the product, lookup tables, and other data that is constant.

ROM 出現(xiàn)在 1965 年，盡管在 256 位時它們并沒有進入許多大眾市場產(chǎn)品。 直到桌面計算器和后來的視頻游戲行業(yè)的誕生，它們才成為大批量零件。 早期的設(shè)備使用二極管矩陣，但后來的設(shè)備采用掩模編程。

雖然當今大多數(shù)系統(tǒng)都需要一定程度的可重編程性，但由于成本的原因，ROM 仍在許多設(shè)備中使用，并且輔以少量的一次性可編程(一次性密碼) 或可重新編程的存儲器，例如閃存。 ROM 電路和實現(xiàn)仍在開發(fā)中，2009 年發(fā)布了一項新**，用于每個單元保持多個位的 ROM 單元，以及 2012 年為 FinFET 設(shè)備實現(xiàn) ROM 的**。