Use of conditions in arrays

#include <stdio.h>

int main() {
    int valores[4][4];
    int i, j, soma;

    for(i = 0; i < 4; i++) {
        for(j = 0; j < 4; j++){
            printf("Informe os valores de [%d, %d]:\n", i + 1, j + 1);
            scanf("%d", &valores[i][j]);
        }
    }
    for(i = 0; i < 4; i++) {                     
        for(j = 0; j < 4; j++) {
            printf("%d\t", valores[i][j]);
        }
        printf("\n");
    }
    for(i = 0; i < 4; i++) {
        soma = 0;
        for(j = 0; j < 4; j++){
            soma += valores[i][j];
        }
        printf("Soma da linha %d: %d\n", i + 1, soma);
    }
    for(i = 0; i < 4; i++) {
        soma = 0;
        for(j = 0; j < 4; j++){
            soma += valores[j][i];
        }
        printf("Soma da coluna %d: %d\n", i + 1, soma);
    }
}

See working on ideone .

There is no error in the condition.

I have organized one in the code because this helps to understand what is happening.

The whole logic of the sum was incorrect. I did not restart the sum variable (which can be the same) at each row / column change. And it was not printing when each sum was finished.

It was not actually adding up, but replacing the value with each pass.

Note that in the first loop I used [i][j] because you need to get each row and then every column of it. In the second I used [j][i] because I need to get each column and then every row of it.

You actually need four somalin and four somacol , one for each row / column in valores .

So, after you've populated the array, you're going to make a% double% to address each element and increment the sum of the row and column.

Walkthrough:

#include <stdio.h>

int
main(int argc, char ** argv) {
    int valores[4][4];
    int i, j, somacol[4], somalin[4];

First we get the values. Here you do this with for and printf() , but you may want to isolate this functionality in a function so in case you want to get these values from a file or something.

    for (i = 0; i < 4; i ++) {
        for (j = 0; j < 4; j ++) {

When calling scanf() and friends, remember to put the format specifier ( printf() in this case); otherwise none of the dynamic values you want to display will appear.

            printf("Informe os valores (%d, %d): ", i + 1, j + 1);

As for %d and the like, remember to always get the string format with a blank space so that it "eats" the carriage return you gave in the previous time called scanf() . Also, since the array is of scanf() , you have to pass the address of the array element (with the int operator):

            scanf(" %d", &(valores[i][j]));
        }
    }

Then, we start all & and somalin to zero so that we can use them with the somacol operator.

    for (i = 0; i < 4; i ++) {
        somalin[i] = somacol[i] = 0;
    }

Now comes the part that interests: We make a% double_de% so that, in the body of the second += , we have the indexes of one of the sixteen elements of for . Simply increment the sum of the row and column corresponding to that element:

    for (i = 0; i < 4; i ++) {
        for (j = 0; j < 4; j ++) {
            somalin[i] += valores[i][j];
            somacol[j] += valores[i][j];
        }
    }

After that, just do anything with the values and return. If you're doing this on for , remember that it returns valores and give main() before exiting. These are good manners.

    for (i = 0; i < 4; i ++) {
        printf("Soma da %dª linha: %d\tSoma da %dª coluna: %d\n", i + 1, somalin[i], i + 1, somacol[i]);
    }

    return 0;
}