Editing Line printer (section)

===== Chain printer =====

'''Chain Printers''' place the type on a horizontally-moving circular chain. As with the drum printer, as the correct character passes by each column, a hammer is fired from behind the paper. Compared to drum printers, chain printers have the advantage that the type chain can usually be changed by the operator. A further advantage is that vertical registration of characters in a line is much improved over drum printers, which need extremely precise hammer timing to achieve a reasonably straight line of print. By selecting chains that have a smaller character set (for example, just numbers and a few punctuation marks), the printer can print much faster than if the chain contains the entire upper- and lower-case alphabet, numbers, and all special symbols. This is because, with many more instances of the numbers appearing in the chain, the time spent waiting for the correct character to "pass by" is greatly reduced. Common letters and symbols appear more often on the chain, according to the [[frequency analysis]] of the likely input. IBM was probably the best-known chain printer manufacturer, and the [[IBM 1403]] is probably the most famous example of a chain printer.<!-- These also can print a complete line by using a chain with 2 moveable pulley different characters were embossed on the chain. -->