Ferranti Mark 1 - Mark 1 Star

Mark 1 Star

After the first two machines a revised version of the design became available, known as the Ferranti Mark 1* or the Ferranti Mark 1 Star. The revisions mainly cleaned up the instruction set for better usability. Instead of the original mapping from holes to binary digits that resulted in the random-looking mapping, the new machines mapped digits to holes in order to produce a much simpler mapping, ø£½0@:$ABCDEFGHIJKLMNOPQRSTUVWXYZ. Additionally several commands that used the index registers had side-effects that led to quirky programming, but these were modified to have no side-effects. Similarly, the original machines' JUMP instructions landed at a location "one before" the actual address, for reasons similar to the odd index behavior, but these proved useful only in theory and quite annoying in practice, and were similarly modified. Input/output was also modified, with 5-bit numbers being output least significant digit to the right, as is typical for most numeric writing. These, among other changes, greatly improved the ease of programming the newer machines. At least seven of the Mark 1* machines were delivered between 1951 and 1957, one of them to Shell labs in Amsterdam.

Tim Berners-Lee's parents both worked on the Ferranti Mark 1 and Mark 1*.