Jumpshot traces its history back to the original version of gist, a program that was delivered with, and only ran on, the BBN Butterfly parallel computer. Gist is still available as part of the TotalView debugging environment, although it is now known as TimeScan. The original version of upshot  was written to provide the most useful feature of gist, its zoomable and scrollable timeline window, in a color version (gist was black-and-white only) that was non-proprietary and would run on any workstation supporting X-windows. (Upshot gets its name from gist, for which it is a synonym .) Over the years upshot expanded to include a number of other features as well . The enhancements were motivated by the development of an application whose highly irregular and input-dependent behavior made an analysis tool of this type indispensable . The logfile generation library developed along with upshot was called ALOG, for Argonne logging.
Upshot originally was written in X (with the Athena widget set). Because it was cumbersome to expand and maintain, we completely rewrote it in the Tcl scripting language, using the Tk companion graphics package . This approach made for extremely rapid development, but the interpreted nature of the language made the graphics component slow when logfiles were large. To deal with this problem, we rewrote the main graphics component of upshot in C, using Tcl's C interface. This rewrite solved the performance problem but introduced a dependency on an unstable part of Tcl itself, as the C interface changed right after the publication of . This version, called nupshot (for new upshot), can still be used, however, if one obtains an earlier version of Tcl/Tk. Until recently, nupshot has been our main performance analysis tool. Upshot, in pure Tcl/Tk, is also still available, but also requires an old version of Tcl. This instability of Tcl/Tk encouraged us to find an alternative.
A few years ago, we rewrote the logging library to improve in multiple ways on ALOG. There was also an intermediate library called BLOG. For historical continuity, therefore, the new package had to be called CLOG (pronounced see-log). It is described in detail in Section Producing Logfiles .