Is it possible to assign the first column of a row of a/a vector/matrix?

Question

taking as an example a two-dimensional vector of the type char 2x2:

char vet[2][2];

Is it possible to assign to the first line indices of this vector? or they work like a pointer to the other rows and columns?

I tried to do it this way

#include <stdio.h>
#include <string.h>


int main(void){
    char v2[2][2];
    v2[0] = 'a'; // LINHA 10
    v2[1] = 'c'; // LINHA 11
    printf("%c\t%c", v2[0], v2[1]);
    return 0;
}

compiler is returning me 2 errors on line 10 and 11

assignment to Expression Whit array type

finally the code does not compile

Answer 1

Assanges, you have to keep in mind that when you are working with matrices you need to pass the full address of the position to which you want to make an assignment. The declaration and use of matrix and vector are different.

char vet[2]; //Isso é um vetor de duas posições
char matriz[2][5]; //Isso é uma matriz com 2 linhas e 5 colunas

Therefore, conceptually we can represent the disposition of the elements in memory in the following way:

A fun Fact about the matrix that we normally don’t need to worry about in PC programming is that although there is this "theoretical" arrangement of the elements in matrix format, the elements are actually arranged in memory spaces sequentially, i.e., for the above example matrix[ 1 ][ 0 ] in memory comes right after matrix[ 0 ][ 4 ]

Another fact about matrices is that when you reference it in this way "matrix[ 1 ]" you are pointing to the value of the memory address. You can test with the example below:

#include <stdio.h>
#include <string.h>


int main(void){
    char v2[2][5];
    printf("%d", v2[0]); //Imprimirá um número X
    printf("\n%d\n", v2[1]); //Imprimirá um número X+5, pois a linha 0 tem 5 colunas

    return 0;
}

But anyway, to assign a value to a position of the matrix you need to pass the position completely. Example:

char matriz[2][3];
matriz[1][2] = 'a';

The result would be:

Answer 2

When you put v2[0] or v2[1], you are not yet referring to a character. To refer to a character, you need to put the two indexes, such as v2[0][0], or v2[1][0].

The guy char[2][] needs two indexes to be transformed into char. Only by a single index will get a reference to a memory region that can not have attribution, so he complains that the attribution to a array cannot occur.

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By the way, the messages seem to refer to the lines:

v2[0] = 'a';
v2[1] = 'c';

since in the print line has no attribution in it.