Secondary storage

"File" -- a bunch of data in order

• text: a bunch of characters
• image file: a bunch of pixels

As opposed to main memory (primary storage), it is:

• larger
• more durable

the idea of "removeable" storage

Why not use only secondary storage?

- MUCH slower.

Disk organization:

• circular "tracks"
• pie-slices are "sectors"
• The intersection of a track and a sector is called a "block". (or sometimes also called a "sector", but that's confusing)

Hierarchical filesystem:

• root directory
• things in a directory can be either "plain files" or directories (subdirectories)

"path name":

"absolute path name": /u/ajr/104/checkq5
"relative path name": checkq5 (if we're starting from /u/ajr/104)
If we're starting from /u/ajr, we could say 104/checkq5

"current directory": where we're starting from.

cd dirname

change the current directory to "dirname", or your home directory if you just type "cd"

mkdir

make a directory

rmdir

removes a directory

rm

removes a plain file

ls

lists files in a directory

Tapes:

• cheap
• large capacity (and removeable media, for more capacity)

Big disadvantage: "sequential"