C/C++ Questions only (Stdio)

Interview Questions

C++ programming on UNIX, C++ Networking,C++ Algorithm Questions and Answers

C/C++ Questions only (Stdio)

1. What's wrong with the code "char c; while((c = getchar()) != EOF)

..."?

2. Why won't the code `` while(!feof(infp)) { fgets(buf, MAXLINE,

infp); fputs(buf, outfp); } '' work?

3. My program's prompts and intermediate output don't always show up

on the screen.

4. How can I read one character at a time, without waiting for the

RETURN key?

5. How can I print a '%' character with printf?

6. How can printf use %f for type double, if scanf requires %lf?

7. How can I implement a variable field width with printf?

8. How can I print numbers with commas separating the thousands?

9. Why doesn't the call scanf("%d", i) work?

10. Why doesn't the code "double d; scanf("%f", &d);" work?

11. How can I specify a variable width in a scanf format string?

12. When I read numbers from the keyboard with scanf "%d\n", it

seems to hang until I type one extra line of input.

13. I'm reading a number with scanf %d and then a string with

gets(), but the compiler seems to be skipping the call to gets()!

14. I'm re-prompting the user if scanf fails, but sometimes it seems

to go into an infinite loop.

15. Why does everyone say not to use scanf? What should I use

instead?

16. How can I tell how much destination buffer space I'll need for

an arbitrary sprintf call? How can I avoid overflowing the destination

buffer with sprintf?

17. Why does everyone say not to use gets()?

18. Why does errno contain ENOTTY after a call to printf?

19. What's the difference between fgetpos/fsetpos and ftell/fseek?

20. Will fflush(stdin) flush unread characters from the standard

input stream?

21. I'm trying to update a file in place, by using fopen mode "r+",

but it's not working.

22. How can I redirect stdin or stdout from within a program?

23. Once I've used freopen, how can I get the original stream back?

24. How can I read a binary data file properly?