Binary I/O (Answers)

Originally created by Idel Martinez and Jerrett Longworth in Fall 2020.

Here is some additional practice using binary I/O. Some of these might take a little bit of thinking, but this practice is here to help you get more comfortable with the material.

Assume big-endian notation.

  1. Let’s start this off simple. Suppose that an int created in C is 4 bytes (32 bits) in size. How would the integer 2 be stored in binary in memory?

Answer: 00000000 00000000 00000000 00000010

  1. Given the previous answer, if a hypothetical program was written to write the integer 2 in binary to a file, what data would be in the file? Write your answer in binary.

Answer: 00000000 00000000 00000000 00000010

  1. Given the following program, what would output.bin contain after execution? Again, write your answer in binary. Assume all necessary libraries are included and all files are opened/closed properly.
struct cool_struct
  int x;

int main(void)
  struct cool_struct basically_just_an_int;
  FILE *ofp = fopen("output.bin", "wb");

  basically_just_an_int.x = 2;

  fwrite(&basically_just_an_int, sizeof(struct cool_struct), 1, ofp);


  return 0;

Answer: 00000000 00000000 00000000 00000010