In the following C program, where the user inputs the value 10, what output does the printf statement produce based on the return value of scanf? main() { int i; printf("%d", scanf("%d", &i)); // value 10 is given as input here }

Introduction / Context:
This question tests your understanding of how standard input functions behave in C, specifically scanf. Many beginners focus only on the values stored in variables and overlook the return value of scanf, which indicates how many input items were successfully read and assigned. The program prints the return value of scanf instead of the value entered, so you must reason about what scanf returns when a single integer is read correctly.

Given Data / Assumptions:

• The user types the value 10 followed by Enter when prompted.
• The code calls scanf with the format string "%d" and the address of an integer i.
• The value read is valid for the %d format and there are no input errors.

Concept / Approach:
In C, scanf returns an integer that represents the number of input items successfully matched and assigned. When using a format string with a single conversion specification such as "%d", scanf returns 1 if it successfully reads and stores an integer, returns 0 if the input does not match the expected format and returns EOF on end of file or error conditions. In this program, printf prints that return value rather than the contents of the variable i.

Step-by-Step Solution:
Step 1: Examine the call scanf("%d", &i). There is exactly one conversion specification in the format string.Step 2: The user enters 10, which is a valid integer, so scanf reads it and stores it in i.Step 3: Because one item is successfully matched and assigned, scanf returns the integer 1.Step 4: printf is called with "%d" as the format and the return value of scanf as the argument.Step 5: Therefore, printf prints 1 to standard output, not 10, so option A is correct.

Verification / Alternative check:
If you modify the program so that it prints both i and the return value, for example by writing printf("value = %d, result = %d", i, scanf("%d", &i)); in a controlled test, you will see that after entering 10 the variable i holds 10 but the result is 1. In more complex format strings such as "%d %f", a successful read might return 2 when both items are correctly read. These experiments confirm that the return value of scanf is the number of successfully assigned input items.

Why Other Options Are Wrong:
Options B, C and D would imply that scanf successfully assigned two, three or four items, which is impossible because the format string contains only one conversion specification. Unless there are multiple % directives in the format string, the maximum successful count cannot exceed one in this case.

Common Pitfalls:
A frequent mistake is to assume that scanf returns the value read rather than the number of items assigned. Another pitfall is ignoring the return value altogether, which makes it harder to detect invalid input or errors. Professional C code often checks the return value of scanf and handles unexpected results gracefully. Remembering how scanf reports success will help you answer similar exam questions correctly.

Final Answer:
1