Questions tagged [null]
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18
questions
0
votes
1
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20
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pset 2 Substitution - extra char(s) in output
So I’ve figured out 99% of the code for the substitution problem. My plaintext input is being output correctly, with the correct enciphered letters and the correct case.
However, I keep getting extra ...
1
vote
1
answer
82
views
Pset4 Recovery Produces Corrupt Null Files & Skips An Image
I've been working at recovery for a while - I believe I'm nearly done with it - but right now my code is giving me serious problems. Currently, running ./recover card.raw produces 49 of the 50 images (...
- 13
0
votes
2
answers
58
views
Week 2 CRACK: Erratic behavior with NULL '\0' when printing combinations of letters
I want to iterate through all possible combinations of the alphabet, including single letter outputs. For this purpose I included the use of '\0' so the first print out in the iteration is the sigle ...
0
votes
1
answer
281
views
pset2 Vigenere null pointer passed as argument 1, which is declared to never be null
So as stated in the title, my problem is that a null pointer is being passed to something in my Vigenere encoder.
Here is my code. I will explain what I find to be the problem and give the error ...
0
votes
1
answer
166
views
CS50 Pset4 Recover card.raw only NULL
Okay so I am starting the recover program from Pset4 and I initially just want to get some output, any output, I have been trying to read the first few bytes from recover.raw but for some reason seem ...
0
votes
1
answer
55
views
When do I nul terminate strings?
I'm on week 4 and looking over other people's codes and I've noticed that up to this point, I've never really nul-terminated strings with '\0'. From what I understand, there are some functions where ...
- 119
0
votes
1
answer
63
views
Speller Trie Seg fault in Unload()
I have implemented load, check, and unload for dictionary.c using trie, and I am suffering a segmentation fault. The error happens inside load function, or, to be more precise, inside the function ...
0
votes
1
answer
50
views
Speller.c fp is NULL
I am done implementing load and check, so I wanted to check it. According debug50, load gives me a boolean value of true, but when speller.c (which was distributed) attempts to open the text file, fp =...
0
votes
1
answer
199
views
String validity check when string is command line argument?
We check the string validity when we use the get_string() function.
Example:
if (p != NULL)
Are we also supposed to check string validity when the string is entered as a command line argument?
0
votes
1
answer
2k
views
What does time(NULL) mean when used with srand48?
What does time(NULL) mean in the following :
srand48((long int)time(NULL)) ?
I see it being used in srand48 when we don't want a seed value.
- 25
0
votes
1
answer
87
views
Pset 2 Caesar Strange Issues
I'm having some issues with Caesar. I can't seem to find anything wrong with my code, however, when I run the program, it prints things that seem to make no sense. When I run check50 on it, it's ...
- 7
0
votes
1
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158
views
Pointers and End of File in Recover.c
recover.c seems to be working just fine. But then I realized I didn't employ a condition which tests the end of file. Why does it still work then? Should I modify my while condition?
In addition to ...
- 21
0
votes
1
answer
92
views
pset4 Recover Cant figure out why jpeg file pointer gets reset to NULL.
Using Error messages and gdb I figured out why I wasnt getting segfaults- img pointer - to the current jpeg file gets set to NULL. Are my loops all wrong? Im getting myself pretty confused. Code ...
- 3
0
votes
1
answer
49
views
Is there a difference between 'NULL' and '\0'?
To put this in context, I'm looking at question 23 of Quiz 0 Fall 2014 (http://cdn.cs50.net/2014/fall/quizzes/0/key0.pdf)
(Don't click the link if you don't want to see the solution! The question is ...
- 192
0
votes
0
answers
59
views
Small question with how NULL works
this is just a small question on NULL. In the snippet below, why doesn't the do-while loop repeat when I don't enter anything for the string?
#include <stdio.h>
#include <string.h>
#...
0
votes
0
answers
68
views
Initializing a variable in a struct, then in a function
It won't allow me to initialize the array to NULL in the struct in the header file:
typedef struct frog
{
bool is_frog;
struct frog* french_chef[10]; // eg = {NULL};
} frog;
which I get, but ...
- 91
1
vote
1
answer
23
views
Bang and Structs
I was hoping someone could clear this up for me, the searches seem to be ignoring the bang.
If I put
while(!NULL)
{
// do this
}
would that be equivalent to saying continue doing this while the ...
- 91
-1
votes
1
answer
436
views
Bad pointer null assignment followed by malloc fail -- WHY?
I'm stumped! In dictionary.c I have coded the load function (with more code that follows the bug, but not needed for this question.) One small block of code is producing a problem! Assigning NULL to ...
- 66.7k