I declare that today, Nov. 19, 2025 is the 50th anniversary of BitBLT, a routine so fundamental to computer graphics that we don't even think about it having an origin. A working (later optimized) implementation was devised on the Xerox Alto by members of the Smalltalk team. It made it easy to arbitrarily copy and move arbitrary rectangles of bits in a graphical bitmap. It was this routine that made Smalltalk's graphical interface possible. Below is part of a PARC-internal memo detailing it:

A scanned PARC-internal memo entitled "Bit BLT."  The full document may be found here: https://www.bitsavers.org/pdf/xerox/alto/BitBLT_Nov1975.pdf
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