What is the output of this C program (assume a pointer is 8 bytes)? #include #include int main() { char *str = "Hello"; printf("%ld, %ld ", strlen(str), sizeof(str)); return 0; }

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BlackTom AI · Accepted Answer

Here we analyze what the program prints by examining the two expressions inside printf.
Option by option, we consider the behavior of strlen and sizeof in this context.

First, strlen(str): Since str is a pointer to the string literal "Hello", strlen computes the length of the string up to the terminating null character. The string "Hello" consists of 5 visible characters: H, e, l, l, o, and then a null terminator, which strlen does not count. Therefore strlen(str) evaluates to 5.

Second, sizeof(str): In the declaration, str is defined as char *str, i.e., a pointer variable. sizeof applied to a pointer yields the size of the pointer itself, not the size of the memory it points to. Given the assumption in the problem that a pointer is 8 bytes, sizeof(str) evaluates to 8.

Now let's evaluate the provided options one by one.
- Option "5, 8": This matches the two computed values exactly: 5 from strlen and 8 from sizeof(pointer) under the given assumption.
- Option "6, 8": This would imply strlen produced 6, which would mean counting the null terminator or miscounting the characters. Neither happens here, so this is incorrect.
- Option "10, 20": Here both numbers are off by a large margin and don’t reflect how strlen or sizeof work for a char pointer in this code.
- Option "8, 5": This reverses the results and also swaps the roles of strlen and sizeof, which is inconsistent with the actual behavior of both operations.

Additionally, note a potential, though minor, portability concern: the code uses %ld to print the values returned by strlen (type size_t) and sizeof (also size_t). On many environments size_t is the same as unsigned long, but strictly speaking the correct format specifier would be %zu for size_t. This doesn’t affect the mathematical results here, but it’s worth mentioning for accuracy in different compilers.

Putting it together, the combination of 5 for the string length and 8 for the pointer size aligns with how strlen and sizeof operate in this snippet under the given assumption.

SP25: CS-149 Sec 03 - Operating Systems CS149 Andreopoulos, Spring 2025 -- Final Exam

What is the output of this C program (assume a pointer is 8 bytes)? #include <stdio.h> #include <string.h> int main() { char *str = "Hello"; printf("%ld, %ld\n", strlen(str), sizeof(str)); return 0; }

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