relative/absolute references

• The reference to a file or directory is often also called its "address" since it indicates the logical position of that file/directory in the hierarchical structure.
• An absolute reference will take you to the same file/directory regardless of the starting point.
1. You can use the / (slash) as the first character of an absolute reference since that will start at the root directory and there can only be one root directory in any given tree (hierarchical) structure.
2. You can use the ~ (tilde) as the first character of an absolute reference since that will start at someone's home directory and there can only be one home directory for each user as indicated in the password file.
• A relative reference will calculated the file/directory addressed based on the current working directory as a starting point.
1. You can use the . (period) as the first character of a relative reference since that will indicate the current working directory explicitly.
2. You can use the .. (period, period) as the first characters of a relative reference since that will indicate the parent of the current working directory.
3. You can use nothing (not ~, ., .. or /) as the first character of the relative reference since that will indicate the current working directory implicitly.
• If you do not know what directory you are in or where that directory is in relation to the destination directory, you must use an absolute reference.
• If you know where the current directory is in relation to the destination directory, it is usually more efficient to use a relative reference..