3     The Ferranti Mark 1 Console

The two larger CRT displays could be switched to show the current contents of any of the 8 pages. The four smaller displays (presumably) permanently showed the current contents of the four auxiliary tubes, A (80-bit Accumulator), B (8 20-bit B-lines), C (Control Address and Present Instruction) and D (current multiplicand value). See the next picture and comment for the Input/Output equipment.