Cicely Mary Williams (née Popplewell; 29 October 1920 – 20 June 1995) was a British software engineer who worked with Alan Turing on the Manchester Mark 1 computer.

[2] She studied the Mathematical Tripos at the University of Cambridge[3][4] where she worked with statistics in the form of punched cards.

[14][15] She wrote the Programmers Handbook for the Ferranti Mark 1 in 1951, reworking Turing's programming manual to make it comprehensible.

[18][19] Popplewell went on to become an advisor and administrator in the newly formed University of Manchester Computing Service where she was remembered as a 'universally liked' mother-figure.

The funeral service was held on 27 June 1995 at St John's church, Buxton, followed by a private cremation.