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Справка Scilab >> call_scilab API (Scilab engine) > Double management

# Double management

How to manage Scilab's variable read and write process using call_scilab and api_scilab

### Description

This help describes how doubles and matrix of doubles can be handle through the Call Scilab API and api Scilab.

There are several functions which can be used to read / write from the memory of Scilab. These functions are described in dedicated pages.

 Note that the default type of a numeric value in Scilab is double. For example, in a=1 or a=[1,2], a will be consider as a double.

### Examples

```/*
* Write a matrix into Scilab
* B=[1 4 2 3;
*    3 9 8 2 ]
* Note that it is done column by column
*/
double B[] = {1,3,4,9,2,8,3,2};   /* Declare the matrix */
int rowB = 2, colB = 4; /* Size of the matrix */
char variableNameB[] = "B";
SciErr sciErr;

/*
* Write it into Scilab's memory
*/
sciErr = createNamedMatrixOfDouble(pvApiCtx,variableNameB,rowB,colB, B); /* pvApiCtx is a global variable */
if(sciErr.iErr)
{
printError(&sciErr, 0);
}

/*
* Prior to Scilab 5.2:
* C2F(cwritemat)(variableNameB, &rowB, &colB, B, strlen(variableNameB));
*/

printf("\n");
printf("Display from Scilab of B:\n");
SendScilabJob("disp(B);"); /* Display B */```
```/* Read the previously declared matrix of double B */
int rowB_ = 0, colB_ = 0, lp_ = 0;
double *matrixOfDoubleB = NULL;
int i = 0, j = 0;
char variableToBeRetrievedB[] = "B";
SciErr sciErr;

/* First, retrieve the size of the matrix */
sciErr = readNamedMatrixOfDouble(pvApiCtx, variableToBeRetrievedB, &rowB_, &colB_, NULL);
if(sciErr.iErr)
{
printError(&sciErr, 0);
}

/*
* Prior to Scilab 5.2:
* C2F(cmatptr)(variableToBeRetrievedB, &rowB_, &colB_, &lp_, strlen(variableToBeRetrievedB));
*/

/* Alloc the memory */
matrixOfDoubleB = (double*)malloc((rowB_*colB_)*sizeof(double));

sciErr = readNamedMatrixOfDouble(pvApiCtx, variableToBeRetrievedB, &rowB_, &colB_, matrixOfDoubleB);
if(sciErr.iErr)
{
printError(&sciErr, 0);
}

/*
* Prior to Scilab 5.2:
*/

printf("\n");
printf("Display from B formated (size: %d, %d):\n",rowB_, colB_);
for(j = 0 ; j < rowB_ ; j++)
{
for(i = 0 ; i < colB_ ; i++)
{
/* Display the formated matrix ... the way the user
* expect */
printf("%5.2f ",matrixOfDoubleB[i * rowB_ + j]);
}
printf("\n"); /* New row of the matrix */
}```