C Programming: %d vs %i in scanf(‪)‬

Why does typing 042 give you 42 with %d but 34 with %i? This beginner-friendly guide walks you through a real C program line by line, revealing the hidden difference between the %d and %i format specifiers in scanf(). You will learn how C handles decimal, octal, and hexadecimal input, why a leading zero changes everything, and which specifier to use in your own programs. Packed with syntax-highlighted code, sample runs, comparison tables, and common pitfalls to avoid.