Login or Register to Ask a Question and Join Our Community


Programming

to get the correct value with unsigned int

Login to Discuss or Reply to this Discussion in Our Community

 
Thread Tools Search this Thread
Top Forums Programming to get the correct value with unsigned int
# 1  
Old 04-11-2007
to get the correct value with unsigned int
hi,

Please help me with the following code to get the difference in values.
Code:
struct a{
		int b1;
		int c1;
		char d1;
	}

main()
{
	unsigned int b=10;
	unsigned int c;
	c = b - (unsigned int )sizeof(a);
  	printf("%d",c);
}

Here c returns some junk value. How can i get the difference between b and sizeof (a) in a positive value without using abs.

Thanks
Last edited by blowtorch; 04-11-2007 at 06:19 AM.. Reason: add code tags
# 2  
Old 04-11-2007
I modified your program slightly to get it to work:
Code:
#include<stdio.h>

struct a {
        int b1;
        int c1;
        char d1;
};

int main() {
        unsigned int b=10;
        unsigned int c;
        c = b - (unsigned int )sizeof(struct a);
        fprintf(stdout,"size of a: %d, size of int: %d, size of char: %d\n",sizeof(struct a),sizeof(int),sizeof(char));
        fprintf(stdout,"%d\n",c);
        return(0);
}

This is the output:
Code:
# ./a.out
size of a: 12, size of int: 4, size of char: 1
-2

Now I agree that for two ints and one char, the size should be 4+4+1=9, but memory allocation is not done a single byte at a time. This is system dependent.
# 3  
Old 04-11-2007
struct size
Hi ,
the solution given above is right but i want to correct at one point.
c = b - (unsigned int )sizeof(struct a);
printf("%d\n",c); will print -2 because any struct occupy the memory in chunk of words. and for linux word is 4 bytes. so for char it occupies 4 bytes give one byte to char and pad the rest 3 bytes so sizeof(struct a) gives 12 as size
Smilie
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. OS X (Apple)

Unsigned to signed, error?...

Hi guys... Macbook Pro, 13", circa August 2012, OSX 10.7.5, default bash terminal. I require the capability to convert +32767 to -32768 into signed hex words... The example piece code below works perfectly except... #/bin/bash # sign.sh # Unsign to sign... while true do # I have used... (2 Replies)
Discussion started by: wisecracker
2 Replies

2. Programming

Unable to assign zero to unsigned character array

Hi, I am unable to assign value zero to my variable which is defined as unsigned char. typedef struct ABCD { unsigned char abc; unsigned char def; unsigned char ghi; } ABCD; typedef ABCD *PABCD; In my Por*C code, i assign the values using memcpy like below ... (3 Replies)
Discussion started by: gthangav
3 Replies

3. Programming

Signed and unsigned intergers

when a date type is considered signed and unsigned is that simple referring to - for signed and positive numbers for unsigned? Further if that is the case would mutiplying and dividing ect where 2 signed numbers, like (-2)*(-2) = 4 result in a unsigned. (3 Replies)
Discussion started by: Fingerz
3 Replies

4. Programming

Comparing unsigned char bits.

/******************************************************************************/ /* Printing an unsigned character in bits */ #include <stdio.h> void display_bits ( unsigned char ); int main() { unsigned char x; /*... (15 Replies)
Discussion started by: robin_simple
15 Replies

5. Programming

Help with understanding ( int, char, long, short, signed, unsigned etc.... )

My question is simple: When should I use a long, int, char, unsigned/signed variables?? When I declare a variable "unsigned;" what did I do it??? Why would I delcare an integer "long" or "short" ( unsigned or signed)?? Any examples of when things like "unsigned", "long", "short" etc...... (6 Replies)
Discussion started by: cpp_beginner
6 Replies

6. Programming

Handle int listen(int sockfd, int backlog) in TCP

Hi, from the manual listen(2): listen for connections on socket - Linux man page It has a parameter called backlog and it limits the maximum length of queue of pending list. If I set backlog to 128, is it means no more than 128 packets can be handled by server? If I have three... (3 Replies)
Discussion started by: sehang
3 Replies

7. Red Hat

cast from const void* to unsigned int loses precision

Hello everey one, here i am attempting to compile a c++ project .it's throughing the following errors. my machine details are as follows: Linux chmclozr0119 2.6.18-53.el5 #1 SMP Wed Oct 10 16:34:19 EDT 2007 x86_64 x86_64 x86_64 GNU/Linux errors: ===== Generating... (0 Replies)
Discussion started by: mannam srinivas
0 Replies

8. UNIX for Dummies Questions & Answers

int open(const char *pathname, int flags, mode_t mode) doubt...

hello everybody! I want to create a file with permissions for read, write, and execute to everybody using C, so I write this code: #include <stdio.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> int main(){ int fileDescriptor; fileDescriptor =... (2 Replies)
Discussion started by: csnmgeek
2 Replies

9. Programming

difference between int ** func() and int *& func()

What is the difference between int** func() and int*& func(). Can you please explain it with suitable example. Thanks, Devesh. (1 Reply)
Discussion started by: devesh
1 Replies

10. Programming

Unsigned int

How can I store and/or print() a number that is larger than 4 294 967 295 in C? is int64_t or u_int64_t what I need ? if, so how can I printf it to stdout? (2 Replies)
Discussion started by: nimnod
2 Replies
Login or Register to Ask a Question