The Baby had a 32-bit word length and a memory of 32 words (1 kibibit). As it was designed to be the simplest possible stored-program computer, the only arithmetic operations implemented in hardware were subtraction and negation; other arithmetic operations were implemented in software. The first of three programs written for the machine calculated the highest proper divisor of 218 (262,144), an algorithm that would take a long time to execute—and so prove the computer's reliability—by testing every integer from 218 downwards, as division was implemented by repeated subtraction of the divisor. The program consisted of 17 instructions and ran for about 52 minutes before reaching the correct answer of 131,072, after the Baby had performed about 3.5 million operations (for an effective CPU speed of about 1100 instructions per second).