The C Programming Language K&R: 4-7 Solution

In this video I go through the solution to the exercise 4-7 from the C Programming Language by Brian Kernighan and Dennis Ritchie. All content is self contained and I have not introduced any content that has not yet been covered in the book. 4-7: Write a routine ungets(s) that will push back an entire string on the input. Should ungets know about buf and buff, or should it just use ungetch?