Assigning values to rows in an array - C programming

Question

Does anyone know how I can make a C program that assigns hexadecimal values to a whole row in a 4x4 array? Each row would have one value.(0x00,0xff, 0x55, and 0xff) It then needs to sum all of the elements which I can do.

#include "msp430g2553.h"

int main(void)
{
  WDTCTL = WDTPW + WDTHOLD;     // Stop watchdog timer
//--------------------------------------------------------------------------
//char type is one byte; int type is two bytes; volatile to prevent optimization
//------------------------------------------------------------------------------

volatile unsigned int i=0, j=0, sum=0;  // sum is the sum of the indices
int Zeroes = 0x00, Ones = 0xff, Odds = 0x55, Evens = 0xaa;
unsigned char ArrayFill [4][4];

//------------------------------------------------------------------------------
//  Initialize ArrayFill to 0xff
//------------------------------------------------------------------------------
{
for (i=0; i<=3; i++)
    for (j=0; j<=3; j++)
        ArrayFill[i][j] = 0xff;
}
//------------------------------------------------------------------------------
//  Fill ArrayFill with the indices values and calculate the sum of the indices
//------------------------------------------------------------------------------
{
for (i=0; i<=3; i++)
    {
    for (j=0; j<=3; j++)
        {
        ArrayFill[i][j] = ????????;
        sum=??????;
        }
    }
}
sum = sum;

Can you do initialization, or must it be assignment? Note that arrays cannot be assigned in C (unless the array is part of a structure). This makes assigning rows to an array hard. Most arrays can be initialized though — VLAs and dynamically allocated arrays can't be initialized formally. — Jonathan Leffler
– Jonathan Leffler, Commented Feb 20, 2017 at 4:41
That is where my problem comes from. The real names for the values above that I need to use are Zeroes, Ones, Odds, and Evens in that order and the compiler does not like that. I can use any method I want, but it doesn't like when I initialize them. — Corey Mack
– Corey Mack, Commented Feb 20, 2017 at 4:45

Bidisha Pyne · Accepted Answer · 2017-02-20 04:55:19Z

0

I would suggest you to initialize the hexadecimal values in unsigned char datatype.

For example:

unsigned char hex[4][4];
    for(i=0;i<4;i++){
            for(j=0;j<4;j++){

                    scan("%s",hex[i][j]);
            }
    }

answered Feb 20, 2017 at 4:55

Bidisha Pyne

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2 Comments

Corey Mack Over a year ago

Could you do an example of a row with one of the values because these are coded not user input via a command window? It only needs the four above.

Corey Mack Over a year ago

I have added what I have so far

sam · Accepted Answer · 2022-03-06 03:04:30Z

Using valarray in C++ as shown below:

#include <iostream>
#include <cstdlib>
#include <iomanip>
#include <valarray>

using namespace std;


int main()
{

volatile unsigned int i=0, j=0, sum=0, g_sum = 0;  // sum is the sum of the indices
int Zeroes = 0x00, Ones = 0xff, Odds = 0x55, Evens = 0xaa;
unsigned char ArrayFill [4][4] = { {0x00,0xff,0x55,0xaa}, {0x00,0xff,0x55,0xaa}, {0x00,0xff,0x55,0xaa}, {0x00,0xff,0x55,0xaa}};

cout << showbase // show the 0x prefix
     << internal // fill between the prefix and the number
     << setfill('0'); // fill with 0s

//    1. Initialization during declaration
for (i=0; i<=3; i++) {
    sum = 0;
    for (j=0; j<=3; j++) {
        sum += ArrayFill[i][j];
    }
    cout << "Row sum: " << hex << setw(12) << sum << endl;
}

//    2. Initialization using a staging variable
valarray<unsigned char> ArrayFill2 [4][4];
unsigned char init[] = {0x00,0xff,0x55,0xaa};
valarray<unsigned char> t(init,4);
for (i=0; i<=3; i++) {
    sum = 0;
    *ArrayFill2[i] = t;
    for (j=0; j<=3; j++) {
        //ArrayFill[i][j] = 0xff;
        sum += ArrayFill[i][j];
    }
    cout << "Row sum: " << hex << setw(12) << sum << endl;
}

//    3. Initializing using staging variable but chaing the type to match the type of sum
valarray<int> ArrayFill3 [4][4];
int init3[] = {0x00,0xff,0x55,0xaa};
valarray<int> t3(init3,4);
for (i=0; i<=3; i++) {
    sum = 0;
    *ArrayFill3[i] = t3;
    sum = (*ArrayFill3[i]).sum();
    cout << "Row sum: " << hex << setw(12) << sum << endl;
}

return 0;
}

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