C :: Calculation Of A Bitwise Expression
Mar 6, 2015
I would like to ask about how we calculates the following bitwise expression.
Code:
unsigned char ch[2] = {0x49,0x49};
ch[0] | ch[1] << 8; I'm thinking ch[1] << 8 as 0x00 ...
So, I think that the above expression converts to 0x49 | 0x00 ... and the complete expression should be 0x49 for me.
But, the compiler gives me the result of 0x4949 as two bytes.How does the compiler calculate this expression as two bytes?show me the steps included in the calculation of this expression?
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Nov 15, 2013
How to do this program i can easily do it in a simple for loop but i have to do this program with the following directions:
1. Write a function called bitN() that returns the value of bit N in number, where number is the first parameter, and N is the second. Assume N of the least significant bit is zero and that both parameters are unsigned int's. (A simple one-liner will suffice)
2. Write a main() function that uses bitN() to convert a decimal integer into its binary equivalent. Obtain the integer to convert from the first command-line argument.
3. Use the expression
unsigned int numBits = sizeof(unsigned int)*CHAR_BIT;
to get the number of bits in an unsigned int. (Include limits.h to get the definition for CHAR_BIT.)
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Dec 8, 2014
Trying to write 4 bytes ints in a binary file and extract them after... I'm using the exclusive or (^) to isolate single bytes to write to and extract from the file since the write() function accepts only chars, only the beginning and end results are not the same...
#include <iostream>
#include <ctime>
#include <fstream>
#include <cstdlib>
using namespace std;
[Code] .....
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Mar 6, 2015
what order a CPU would process the following arithmetic problem: 5 - (-9) = 14? Would the CPU recognize that the 'minus a minus' combination simply represents 5 + 9, and proceed with that addition, or would the CPU have to first calculate the 2's complement of -9, and then proceed to take the 2's complement of that first result in order to complete the calculation of the addition of the 'double negative'?
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Feb 9, 2015
1.The operands from << and >> may be any of integer type (including char) The integer promotions are performed on both operands the result has the type of the left operand after promotion.
It means that if we have z = x >> y then sizeof(z) == sizeof(x) ?
2. The ~ operator is unary the integer promotions are performed on its operand.
So if I have short int y; and int x=1; y = ~x what is the meaning here?
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Feb 2, 2015
Let's examine the code.
int x = 100;
unsigned long answer1 = ~x;
unsigned long long answer2 = ~x;
cout << (bitset<32>) x << "
[Code] .....
Shouldn't the decimal of answer 1 and 2 the same thing?
I get 4294967195 for answer1 and 18446744073709551515 for answer 2.
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Feb 13, 2014
I have a project assignment for school to write a program that does number conversions using bitwise operators. The premise is that the user enters a number with one of three letter prefixes -- Q1232, O6322, H762FA, etc. -- and the program will take that number and convert it to the other two number bases. Q is for quarternary, O is for octal, and H is for hexadecimal. The transformations should be done using bitwise operators and bit shifting. I am guessing I need to scan the number, convert it to binary, then convert it to the other two bases.
However, I am completely new to bitwise operators and bit shifting, so how to convert numbers of different bases to binary and then binary to other bases using these bit and bitwise functions. I don't have much code done yet, since I am still unsure of how to approach it, but I'll post what little I have.
Here it is:
#include <stdio.h>
#include <string.h>
int main() {
char numType;
printf("
The user will enter a number up to 32 digits in quarternary
");
printf("(base 4), octal (base 8), or hexadecimal (base 16). If in
");
[Code] ....
I figure in each case I can write a function that converts the entered number to binary, then maybe two more functions that convert said binary number to the other bases. For default in the switch I will tell the user they entered an invalid number. I don't have the program looping until the user types 'EXIT' yet, but I will once I figure out anything about these bitwise operators.
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Oct 30, 2014
I'm doing a bitwise operations on 2 bytes in a buffer, then storing the result in a variable. However, I sometimes get a non-zero value for the variable even though I'm expecting a zero value.
The relevant portion of the code is as follows.
unsigned int result = 0;
long j = 0, length;
unsigned char *data;
data = (unsigned char *)malloc(sizeof(unsigned char)*800000);
[Code] ......
I'm expecting result to be zero when my data[j] and data[j+1] are 0xb6 and 0xab respectively, which is the case for most of the time. However, for certain values of j, my result is strangely not zero.
j = 62910, result = 64
j = 78670, result = 64
j = 100594, result = 64
j = 165658, result = 512
j = 247990, result = 128
j = 268330, result = 512
j = 326754, result = 1
j = 415874, result = 256
j = 456654, result = 1024
j = 477366, result = 512
It appears that these strange result values are all powers of 2, with a 1 bit appearing somewhere in the unsigned int.
I'm not changing the value of result anywhere else in the code, and when I print out (unsigned int)(((data[j]^0xb6)<<8)|(data[j+1]^0xab)), I get 0, but somehow when it gets stored in result, it's no longer zero.
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May 22, 2013
What is the difference between at performance level, if any, between the following cases, during assignment?
case 1: #define Value_16 16
and
case 2: #define Value_16 (1<<4)e.
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Jun 1, 2012
I have a 32 bit integer variable with some value (eg: 4545) in it, now I want to read first 8 bits into uint8_t and second 8 bits into another uint8_t and so on till the last 8 bits.
I am thinking of using bitwise operators...
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Feb 24, 2012
I have a doubt in Left Shift Operator
int i = 1;
i <<= (sizeof (int) *8);
cout << i;
It prints 1.
Doubt:
i has been initialized to 1.
And while moving the bits till the size of the integer, it fills the LSB with 0's and as 1 crosses the limit of integer, i was expecting the output to be 0.
How and Why it is 1?
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Mar 30, 2013
how to show all the bits of a number using bitwise shift operator....and hence represent the number in 2's complement representation
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Jul 16, 2014
In a .h file there is a function that takes in this parameter:
void (^callback)(float * arg)=NULL
as in a function definition:
void func(void (^callback)(float * arg)=NULL);
What I am able to read is that it takes a function pointer and if not defined it overrides with NULL. The part I do not get is the ^ in (^callback). I only know ^ as a bitwise XOR operator. It also generates issues in my VS2012 compiler (something with CLR). So I would really like to rewrite this part to something else, without the bitwise operator...
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Oct 30, 2014
I'm doing a bitwise operations on 2 bytes in a buffer, then storing the result in a variable. However, I sometimes get a non-zero value for the variable even though I'm expecting a zero value. The relevant portion of the code is as follows.
Code:
unsigned int result = 0;
long j = 0, length;
unsigned char *data;
data = (unsigned char *)malloc(sizeof(unsigned char)*800000);
[Code] ....
I'm expecting result to be zero when my data[j] and data[j+1] are 0xb6 and 0xab respectively, which is the case for most of the time. However, for certain values of j, my result is strangely not zero.
Code:
j = 62910, result = 64
j = 78670, result = 64
j = 100594, result = 64
j = 165658, result = 512
j = 247990, result = 128
j = 268330, result = 512
j = 326754, result = 1
j = 415874, result = 256
j = 456654, result = 1024
j = 477366, result = 512
It appears that these strange result values are all powers of 2, with a 1 bit appearing somewhere in the unsigned int.
I'm not changing the value of result anywhere else in the code, and when I print out
Code: (unsigned int)(((data[j]^0xb6)<<8)|(data[j+1]^0xab))
I get 0, but somehow when it gets stored in result, it's no longer zero. I really don't understand what could be wrong.
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Jan 3, 2014
i need to calculate crc32 of a input file and check with the original crc value of a file and return true/false,
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Aug 8, 2013
I tried to write a simple program to calculate monthly yield, APR, and principle in various directions. Anyway, here's some code to get the APR from the principle and monthly yield. When I run it though, it spits 0 at me every time! What the problem is; the other functions work just fine and the code line for the APR calculation is just what it ought to be - I see neither a math nor tech problem here.
Here is the offending function:
Code:
void calculateAPR() {
int principle, monthlyYield, apr;
cout<<"
Please input the principle:";
cin>>principle;
cin.ignore();
[code]....
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Apr 9, 2014
I want to have calculations take place inside a switch statement that calls the appropriate function. The menu portion of the program works well, but I can't figure out how to let the user actually input 2 different numbers to the functions. My questions are:
1. If I use scanf to assign values to the variables, what determines end of input to each variable? (ie.. scanf("%d%d", &a, &b) what is the end of a, what is the end of b?)
2. Should I assign the variables to user input inside the switch, or try to do it in the functions below?
3. Is there something I haven't thought to ask that will screw me over? I'm really new to this.
Code:
#include<stdio.h>
int add(int b, int a);
int mult(int b, int a);
main() {
[Code] ....
This really was a test of multilayer menu, but I want to add functionality if I can.
Changed a variable before posting and didn't change all the conditions testing it.
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Dec 17, 2013
void viewWasteReport(){
EXEC SQL BEGIN DECLARE SECTION;
char wasteid[5],wastetype[31],month[11],wastequantity[13],wasteweight[11];
//double wastequantity[13];
//double wasteweight[11];
EXEC SQL END DECLARE SECTION;
fnConnectDB();
[Code] ....
I want to obtain the the product of wastequantity*wasteweight, but i get error.
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Aug 1, 2013
I am trying to calculate a CRC of a Base64 string.I give you the correct checksum : 2942042514...And now the string :
AQAAAAAAAABsYAAAAAAAAENvbXByZXNzZWRUaXRsZQB4nO0d2XIaSbI+hZ13
m0NCR0QNE7KOHcXKlkMwtnhyIIRkdjGwgGxpP35386jqursRsk0zQygkd+dR
lVmVmZVdl//3Xyl+E4/iixiJivgqBmIm5mIoJmIsfhW/iLp4LWrwbwUwY9EH
[code]....
I tried CRC 16, 32 and with polynomial 0xEDB88320L, and with all these tries, I cannot find the correct checksum, it is my main problem.I don't want C++ code source, but I am searching for the method or algorithm to find it. If you want to know, this string in base64 contains an string compressed in zip, which contains an UTF16 XML. I want to modify information, and modify Adobe Projet (prproj)
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Oct 1, 2014
#include <iostream>
#include <iomanip>
#include <string>
#include <cmath>
[Code]....
Write a program that outputs inflation rates for two successive years and whether the inflation is increasing or decreasing. Ask the user to input the current price of an item and its price one year and two years ago.
To calculate the inflation rate for a year, Uh, no, that’s wrong! To calculate the inflation rate for a year, subtract the price of the item ONE YEAR AGO from the price of the item for that year and then divide the result by the price a year ago. For example: 2014-Inflation-Rate = (2014-Price minus 2013-Price) / 2013-Price.
Your program must contain at least the following functions:
•a function to get the input
•a function to calculate the results
•a function to output the results
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Dec 9, 2014
I need to create average calculating program using do while loop.
t = 1 - sin(x) when x > 0;
t = 1 + x when x = 0;
t = a + sin(x) when x < 0;
primary information:
x changes from 1 to -1 by step h = -0.5, a = -2
#include <iostream>
#include <stdio.h>
#include <math.h>
using namespace std;
int main() {
int a = -2;
[Code] ....
How this program should look that's why this probably looks just like a mess.
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Aug 1, 2013
I am trying to calculate a CRC of a Base64 string. I know the answer of the checksum, but I don't how to calculate it (It is for Adobe project).
I give you the correct checksum : 2942042514
And now the string :
AQAAAAAAAABsYAAAAAAAAENvbXByZXNzZWRUaXRsZQB4nO0d2XIaSbI+hZ13
m0NCR0QNE7KOHcXKlkMwtnhyIIRkdjGwgGxpP35386jqursRsk0zQygkd+dR
lVmVmZVdl//3Xyl+E4/iixiJivgqBmIm5mIoJmIsfhW/iLp4LWrwbwUwY9EH
+C1gx+KesH+IjjgTr4Bqj2h+Ey0hxRHQTMQNcHwSV/A0EYsA3oFSFlDngDAf
[Code] ....
I tried CRC 16, 32 and with polynomial 0xEDB88320L, and with all these tries, I cannot find the correct checksum, it is my main problem.
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May 13, 2013
Is there any possible way of calculating some values at compile time? I have the following code of genereting upto 2000000010 palindrome numbers.
Code:
#include <iostream>
#include <string>
#include <sstream>
#include <string.h>
#include <stdlib.h>
[Code] .....
As you see, I have taken input from the user just after calculating the whole palindromes. So cant we calculate this at compile time? because runtime of this program is extremely slow.
Another qs. I first tried to use array but It didnt allow 2*10^9 sized array. so what should I do whenever I need that size of array?
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Feb 8, 2014
I wrote a function to do factorization (n!). while this function works perfectly:
Code:
int fact (double x){
register int z=1;
if (x==0)
return 1;
else
for(x;x;x--)
z*=x;
return z;
}
this doesn't:
Code:
int fact (double x){
if (x==0)
return 1;
else
for(x;x;x--)
x*=x;
return x;
}
what makes the second one different from the first one? can't see the difference..
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Mar 24, 2014
Why do i keep getting wrong results
Code:
#include "stdafx.h"#include <stdio.h>
#include <string.h>
nt main(void){
char name[40];
int numbers[50];
[Code] .....
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Apr 26, 2013
I am basically trying to make a program for a calculator. I am struggling with how to do the sine calculation. this calculation will take place at line 158.
#include <iostream>
#include <cmath>
using namespace std;
int main() {
double firstNumber = 0.0;
double secondNumber = 0.0;
char operation =' ';
[Code] ....
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