c - Converting integer to string with atoi/sprintf -

this not whole code sum easy see. have no problem convert string integer cannot convert integer string. program crashes. here code. @ line itoa.

#include <stdio.h> #include <stdlib.h> #include <ctype.h> #include <string.h>  #define sizex 49 #define sizey 6  int main() {     size_t x, y;     char *a[50][7];     char name[50][100];     char surname[50][100];     char in[50][100];     char yob[50][100];     char usname[50][100];     char pass[50][100];     char totamount[50][100];      (x = 0; x <= sizex; x++) {                  a[x][0] = name[x];         a[x][1] = surname[x];         a[x][2] = in[x];         a[x][3] = yob[x];         a[x][4] = usname[x];         a[x][5] = totamount[x];         a[x][6] = pass[x];     }     printf("\nplease enter name of new user\n");     scanf(" %s", a[0][0]);      printf("please enter surname of new user\n");     scanf(" %s", a[0][1]);      printf("please enter identity number of new user\n");     scanf(" %s", a[0][2]);      printf("please enter year of birth of new user\n");     scanf(" %s", a[0][3]);      printf("please enter username of new user\n");     scanf(" %s", a[0][4]);      strcpy(a[0][6], a[0][4]);     strrev(a[0][6]);      a[0][5] = "0";      int z;     z = atoi(a[0][5]);     z = z + strlen(a[0][4]) * 10;      itoa(z, a[0][5], 10);     //sprintf(a[0][5], "%d", z);      printf("%s\n", a[0][5]);     printf("%d\n", z);      return 0; } 

by doing this:

a[0][5]="0"; 

you assigning a[0][5] pointer readonly memory containing string literal "0".

here:

itoa( z, a[0][5],10 ); 

you attempting write there, giving memory access violation.