code not workingI am trying to scroll alphabets using one 8x8 led matrix and 74

I am trying to scroll alphabets using one 8x8 led matrix and 74595
but I have a problem in my code
basically I have formed an array for an alphabet representing the binary numbers for each row corresponding to the alphabet.
then I have shifted them and stored them in an another array.
here is my code....

#include <TimerOne.h>
int latchPin = 8; //Pin connected to Pin 12 of 74HC595 (Latch)
int clockPin = 12; //Pin connected to Pin 11 of 74HC595 (Clock)
int dataPin = 11; //Pin connected to Pin 14 of 74HC595 (Data)
byte frame = 0; // variable to store the current frame being displayed
int k=7;
byte _A[13][8],_B[13][8],_C[13][8],_D[13][8],_E[13][8],_F[13][8],_G[13][8],_H[13][8],_I[13][8],_J[13][8],
_K[13][8],_L[13][8],_M[13][8],_N[13][8],_O[13][8],_P[13][8],_Q[13][8],_R[13][8],_S[13][8],
_T[13][8],_U[13][8],_V[13][8],_W[13][8],_X[13][8],_Y[13][8],_Z[13][8];
byte A[8]={56,68,68,68,124,68,68,0};
byte B[8]={120,68,68,120,68,68,120,0};
byte C[8]={56,68,64,64,64,68,56,0};
byte D[8]={120,68,68,68,68,68,120,0};
byte E[8]={124,64,64,120,64,64,124,0};
byte F[8]={124,64,64,120,64,64,64,0};
byte G[8]={56,68,64,64,92,68,56,0};
byte H[8]={68,68,68,124,68,68,68,0};
byte I[8]={124,16,16,16,16,16,124,0};
byte J[8]={4,4,4,4,68,68,56,0};
byte K[8]={68,72,80,96,80,72,68,0};
byte L[8]={64,64,64,64,64,64,124,0};
byte M[8]={68,108,84,84,68,68,68,0};
byte N[8]={68,68,100,84,76,68,68,0};
byte O[8]={56,68,68,68,68,68,56,0};
byte P[8]={120,68,68,120,64,64,64,0};
byte Q[8]={56,68,68,68,84,76,60,0};
byte R[8]={120,68,68,120,80,72,68,0};
byte S[8]={56,68,64,56,4,68,56,0};
byte T[8]={124,16,16,16,16,16,16,0};
byte U[8]={68,68,68,68,68,68,56,0};
byte V[8]={68,68,68,68,68,40,16,0};
byte W[8]={68,68,68,84,84,108,68,0};
byte X[8]={68,68,40,16,40,68,68,0};
byte Y[8]={68,68,68,40,16,16,16,0};
byte Z[8]={124,4,8,16,32,64,124,0};
 void setup() 
 {
  pinMode(latchPin, OUTPUT); // set the 3 digital pins to outputs
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
  Timer1.initialize(6000); // set a timer of length 10000 microseconds
  Timer1.attachInterrupt(screenUpdate); // attach the screenUpdate function
  for(int i=0;i<=12;i++)
  {
    if(i>=0&&i<=7)
    {
    for(int j=0;j<=7;j++)
    {
      _A[i][j]=A[j]>>k;
      _B[i][j]=B[j]>>k;
      _C[i][j]=C[j]>>k;
      _D[i][j]=D[j]>>k;
      _E[i][j]=E[j]>>k;
      _F[i][j]=F[j]>>k;
      _G[i][j]=G[j]>>k;
      _H[i][j]=H[j]>>k;
      _I[i][j]=I[j]>>k;
      _J[i][j]=J[j]>>k;
      _K[i][j]=K[j]>>k;
      _L[i][j]=L[j]>>k;
      _M[i][j]=M[j]>>k;
      _N[i][j]=N[j]>>k;
      _O[i][j]=O[j]>>k;
      _P[i][j]=P[j]>>k;
      _Q[i][j]=Q[j]>>k;
      _R[i][j]=R[j]>>k;
      _S[i][j]=S[j]>>k;
      _T[i][j]=T[j]>>k;
      _U[i][j]=U[j]>>k;
      _V[i][j]=V[j]>>k;
      _W[i][j]=W[j]>>k;
      _X[i][j]=X[j]>>k;
      _Y[i][j]=Y[j]>>k;
      _Z[i][j]=Z[j]>>k;
    }
    k--;
    if(k<0)
    {k=0;}
    }
    if(i>=8&&i<=12)
    {
     k++; 
    for(int j=0;j<=7;j++)
    {
     _A[i][j]=A[j]<<k;
     _B[i][j]=B[j]<<k;
     _C[i][j]=C[j]<<k;
     _D[i][j]=D[j]<<k;
     _E[i][j]=E[j]<<k;
     _F[i][j]=F[j]<<k;
     _G[i][j]=G[j]<<k;
     _H[i][j]=H[j]<<k;
     _I[i][j]=I[j]<<k;
     _J[i][j]=J[j]<<k;
     _K[i][j]=K[j]<<k;
     _L[i][j]=L[j]<<k;
     _M[i][j]=M[j]<<k;
     _N[i][j]=N[j]<<k;
     _O[i][j]=O[j]<<k;
     _P[i][j]=P[j]<<k;
     _Q[i][j]=Q[j]<<k;
     _R[i][j]=R[j]<<k;
     _S[i][j]=S[j]<<k;
     _T[i][j]=T[j]<<k;
     _U[i][j]=U[j]<<k;
     _V[i][j]=V[j]<<k;
     _W[i][j]=W[j]<<k;
     _X[i][j]=X[j]<<k;
     _Y[i][j]=Y[j]<<k;
     _Z[i][j]=Z[j]<<k;
    }
    }
 }
 }
void loop() {

if (frame>12) { 
    frame =0;
  }

  delay(100);
      frame++;
 }
void screenUpdate() { // function to display image
  byte row = B10000000; // row 1
  for (byte k = 0; k < 9; k++) {
    digitalWrite(latchPin, LOW);
    shiftOut(11,12,LSBFIRST,~_A[frame][k]);
    shiftOut(11,12,LSBFIRST,row);
    digitalWrite(latchPin, HIGH);
    row = row >> 1;
  }
}

when I write alphabets from A-Z in for loop written in setup code does not work
but when I write from A-H code works.
even writing "I" after H screws up the code.
please tell me where I am doing wrong

You're trying to squeeze a quart into a pint pot.
Add up all the array sizes, and compare to the amount of RAM on your processor.