單片機是指一個集成在一塊芯片上的完整計算機系統(tǒng)。盡管他的大部分功能集成在一塊小芯片上，但是它具有一個完整計算機所需要的大部分部件：CPU、內(nèi)存、內(nèi)部和外部總線系統(tǒng)，目前大部分還會具有外存。同時集成諸如通訊接口、定時器，實時時鐘等外圍設(shè)備。而現(xiàn)在最強大的單片機系統(tǒng)甚至可以將聲音、圖像、網(wǎng)絡(luò)、復雜的輸入輸出系統(tǒng)集成在一塊芯片上。
單片機也被稱為微控制器（Microcontroller），是因為它最早被用在工業(yè)控制領(lǐng)域。單片機由芯片內(nèi)僅有CPU的專用處理器發(fā)展而來。最早的設(shè)計理念是通過將大量外圍設(shè)備和CPU集成在一個芯片中，使計算機系統(tǒng)更小，更容易集成進復雜的而對提及要求嚴格的控制設(shè)備當中。INTEL的Z80是最早按照這種思想設(shè)計出的處理器，從此以后，單片機和專用處理器的發(fā)展便分道揚鑣。
早期的單片機都是8位或4位的。其中最成功的是INTEL的8031，因為簡單可靠而性能不錯獲得了很大的好評。此后在8031上發(fā)展出了MCS51系列單片機系統(tǒng)?；谶@一系統(tǒng)的單片機系統(tǒng)直到現(xiàn)在還在廣泛使用。隨著工業(yè)控制領(lǐng)域要求的提高，開始出現(xiàn)了16位單片機，但因為性價比不理想并未得到很廣泛的應(yīng)用。90年代后隨著消費電子產(chǎn)品大發(fā)展，單片機技術(shù)得到了巨大的提高。隨著INTEL i960系列特別是后來的ARM系列的廣泛應(yīng)用，32位單片機迅速取代16位單片機的高端地位，并且進入主流市場。而傳統(tǒng)的8位單片機的性能也得到了飛速提高，處理能力比起80年代提高了數(shù)百倍。目前，高端的32位單片機主頻已經(jīng)超過300MHz，性能直追90年代中期的專用處理器，而普通的型號出廠價格跌落至1美元，最高端的型號也只有10美元。當代單片機系統(tǒng)已經(jīng)不再只在裸機環(huán)境下開發(fā)和使用，大量專用的嵌入式操作系統(tǒng)被廣泛應(yīng)用在全系列的單片機上。而在作為掌上電腦和手機核心處理的高端單片機甚至可以直接使用專用的Windows和Linux操作系統(tǒng)。
Refers to an integrated single-chip at a chip on the integrity of computer systems. Even though most of his features at a small chip on, but it has a complete computer most of the necessary components: CPU, memory, internal and external bus system, most will have the Core. At the same time, such as integrated communication interfaces, timers, real-time clock and other peripheral equipment. And now the most powerful single-chip microcomputer system can even voice, image, network, complex input and output of system integration on a single chip. Also known as single-chip microcontroller, because it is the first to be used in the field of industrial control. Single-chip by chip dedicated processor CPU only evolved. The first design concept through to a large number of peripherals and CPU in a single chip, the computer system so that smaller, more easily integrated into the complex and demanding with regard to the reference control devices. INTEL the Z80 is one of the earliest in accordance with this idea to design the processor, From then on, the MCU and the development of a dedicated processor parted ways. Early single-chip 8-bit or all of four. One of the most successful are Intel's 8031, because the performance of a good reliable and easy access to great acclaim. Later on in 8031 developed a series of single-chip microcomputer system MCS51. Based on single-chip microcomputer system of the system is still widely used until now. As the field of industrial control requirements improve, beginning a 16-bit single-chip, but not ideal because cost-effective has not been very widely used. After the 90's with the big consumer electronics product development, single-chip technology has been enormous improve. With INTEL i960 series, especially the later series of widely used ARM,