There are two main types of production systems: continuous and intermittent. Continuous production systems operate constantly without halts, producing goods on a large scale based on demand forecasts rather than customer orders. Examples include mass and process production flows like those in food and fuel industries. Intermittent production systems produce goods in small batches based on customer orders, with irregular production flows that are flexible and can produce a wide variety of customized products of different sizes and designs. Types of intermittent systems are project, job order, and batch production.