Final answer:
The scanf() function returns an int indicating the number of items successfully read, while getchar() also returns an int, which is the next character from input or EOF in case of file end or error.
Step-by-step explanation:
The scanf() function in the C programming language returns an int data type, which represents the number of items successfully read and assigned. The function, therefore, will return the count of successfully scanned input items, or EOF (end-of-file indicator) if an input failure occurs before the first receiving argument was assigned.
The getchar() function, on the other hand, returns an int data type as well. However, the purpose of this return value is different from scanf(). The value returned by getchar() is the next available character from the standard input stream (stdin), or EOF if the end of the file or an error occurs.