CompuServe introduced GIF to replace its earlier black-and-white image format, run-length encoding, abbreviated RLE.
GIF was developed by a CompuServe team led by computer scientist Steve Wilhite and released on June 15, 1987. The new format was intended for color images in CompuServe’s file-download areas, where users often relied on slow modems. Replacing the earlier black-and-white RLE format made color image exchange more practical.
RLE means run-length encoding, a compression method that represents repeated values as a value and a count. GIF instead became famous for using Lempel-Ziv-Welch, or LZW, lossless compression. GIF also supported palettes of up to 256 colors, making it well suited to logos, illustrations, and simple graphics.
A common mix-up is confusing RLE with PCX. PCX also used run-length encoding, but the question asks for CompuServe’s earlier black-and-white format. The original GIF specification was called GIF87a; GIF89a later added features such as animation timing and transparency.