The mandatory index component, also called a parameterspecifier, is a number starting from 0 that identifies a corresponding item in the list of objects.
强制“索引”组件(也叫参数说明符)是一个从0开始的数字，可标识值列表中对应的元素。
2
The type of each parameter must match its format specifier.
每个参数的类型必须匹配它的格式指定者。
3
If a type specifier immediately follows a left parenthesis, that parenthesis is the start of a function descriptor and the type is part of a function parameter.