A programmable logic controller (PLC) or programmable controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or lighting fixtures. PLCs are used in many industries and machines. Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed or non-volatile memory. A PLC is an example of a real time system since output results must be produced in response to input conditions within a bounded time, otherwise unintended operation will result.
1.History
The PLC was invented in response to the needs of the American automotive manufacturing industry. Programmable logic controllers were initially adopted by the automotive industry where software revision replaced the re-wiring of hard-wired control panels when production models changed.


可編程邏輯控制器（PLC）或可編程序控制器是用于機(jī)電過程自動(dòng)化的數(shù)字計(jì)算機(jī)，例如控制機(jī)械廠生產(chǎn)線、游樂設(shè)施或照明裝置?？删幊炭刂破髟谠S多工業(yè)和機(jī)器中使用。與通用的計(jì)算機(jī)不同的是，PLC是專為多個(gè)輸入和輸出管理，擴(kuò)展溫度范圍、不受電磁噪音影響、抗震動(dòng)和沖擊所設(shè)計(jì)。控制器的操作程序通常存儲(chǔ)在電池供電或非易失性的內(nèi)存中。PLC是實(shí)時(shí)的系統(tǒng)，因?yàn)橄到y(tǒng)產(chǎn)生的輸出結(jié)果必須在有限的時(shí)間內(nèi)回饋到輸入，否則會(huì)導(dǎo)致錯(cuò)誤操作。
1.歷史
PLC發(fā)明是針對(duì)于美國(guó)汽車制造行業(yè)的需要?？删幊踢壿嬁刂破髯畛跬ㄟ^了在軟件版本更換硬連線的控制板生產(chǎn)模式更改時(shí)的汽車工業(yè)。