[header] How to write capital and lowercase letters in binary [title] Consult an ascii conversion chart. [step] Before you convert a letter into binary, you first need to know its numerical representation in the ascii (or american standard conversion for information interchange) chart. The ascii assigns numerical representations to a variety of generic symbols, including letters. 
These numerical representations start at 0 and end with 225. Search for a given letter (let's say " a ") in the " character " column, which may be abbreviated to " chr.