previous |
start |
next
MIME Types and Encodings
The Content-Type: header in MIME specifies a "MIME
type" for the data which follows. The MIME type is used to open a
suitable application program to display the attached data. Some
standard MIME types include:
text/plain |
lines of ASCII text |
text/html |
HTML text |
image/gif |
GIF image |
video/mpeg |
MPEG video |
application/postscript |
PostScript document |
application/octet-stream |
Arbitrary data |
For non-ASCII (8 bit) data, common encodings include
"quoted-printable" and "Base64".
In Base64 encoding, the message is subdivided into groups of 3
bytes (24 bits) in length. These 24 bits are then subdivided into 4
groups of 6 bits each. Each 6 bit group is represented as one of 64
printable ASCII characters, from the 95 printable characters in
ASCII. Finally, each of the printable characters is sent as an 8
bit byte. Thus, 24 bits of data are sent as 32 bits of ASCII data
in the encoded message.
previous |
start |
next