Final answer:
The return type of printf() is an integer indicating the number of characters printed, while putchar() returns the character written or EOF on error, providing a mechanism for error checking and handling in C programming.
Step-by-step explanation:
The return type of the printf() and putchar() functions in C programming language conveys specific information about the outcome of these functions. The printf() function returns an integer that represents the number of characters successfully printed, or a negative value if there is an error. Conversely, the putchar() function returns the character written as an unsigned char cast to an int or EOF on error. Understanding these return values is crucial as they allow you to check whether the functions have executed correctly and handle any errors accordingly.