Run-length encoding in the context of Lossless data compression

CompuServe, Inc. (CompuServe Information Service, Inc., also known by its initialism CIS or later CSi) was an American Internet company that provided the first major commercial online service. It opened in 1969 in Columbus, Ohio, as a timesharing and remote access service marketed to corporations. After a successful 1979 venture selling otherwise under-utilized after-hours time to Radio Shack customers, the system was opened to the public, roughly the same time as The Source.

H&R Block bought the company in 1980 and began to advertise the service aggressively. CompuServe dominated the industry during the 1980s, buying their competitor The Source. One popular use of CompuServe during the 1980s was file exchange, particularly pictures. In 1985, it hosted one of the earliest online comics, Witches and Stitches. CompuServe introduced a simple black-and-white image format known as RLE (run-length encoding) to standardize the images so they could be shared among different types of microcomputers. With the introduction of more powerful machines enabling display of color, CompuServe introduced the much more capable Graphics Interchange Format (GIF), invented by Steve Wilhite. GIF later became the most common format for 8-bit images transmitted by Internet during the early and mid-1990s.

A binary image is a digital image that consists of pixels that can have one of exactly two colors, usually black and white. Each pixel is stored as a single bit — i.e. either a 0 or 1.

A binary image can be stored in memory as a bitmap: a packed array of bits. A binary image of 640 × 480 pixels has a file size of only 37.5 KiB, and most also compress well with simple run-length compression. A binary image format is often used in contexts where it is important to have a small file size for transmission or storage, or due to color limitations on displays or printers.