Final answer:
To write a program that prints out the letters of a word on a single line, separated by two underscores, you can use a loop to iterate through each letter of the word.
Step-by-step explanation:
To write a program that prints out the letters of a word on a single line, separated by two underscores, you can use a loop to iterate through each letter of the word. Here is an example program in Python:
word = input('Enter a word: ') # get input from the user
for letter in word:
print(letter, end='__') # print each letter followed by two underscores
For example, if the user enters the word 'hello', the output will be 'h__e__l__l__o__'.