The "getchar" function does not work for me - c

Question

I designed a simple program in c but although it compiles fine, it doesn't work well and I would like to know why.
Perhaps the function getchar doesn't work. It's what I believe. I execute this program in my computer windows 11 in msys2-mingw_86. In the screen everything is fine until i try to modify the array. Then appears in the screen any number everytime i run the program. It's always a different number. Can somebody help me, please ?
I hope someone tell me the correct way in c in windows 11 of to use function "getchar" because I think this is what's wrong.
Thank you.
This is the program:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#define CLEAR() printf("\033[2J")
#define MOVEUP(x) printf("\033[%dA", (x))
#define MOVEDOWN(x) printf("\033[%dB", (x))
#define MOVELEFT(y) printf("\033[%dD", (y))
#define MOVERIGHT(y) printf("\033[%dC",(y))
#define MOVETO(x,y) printf("\033[%d;%dH", (x), (y))
#define RESET_CURSOR() printf("\033[H")
#define HIDE_CURSOR() printf("\033[?25l")
#define SHOW_CURSOR() printf("\033[?25h")
#define HIGHT_LIGHT() printf("\033[7m")
#define UN_HIGHT_LIGHT() printf("\033[27m")
#define NUM_MAX 6
static void modificacion(int matriz[10][10], int fil, int col)
{
char letras;
int B;
CLEAR();
int x=0;
int y=0;
for (int i=0;i<fil;i++){
x=4;
y=y+1;
for (int j=0;j<col;++j){
MOVETO(y,x-3);
printf("%d",matriz[y-1][(x/4)-1]);
x=x+4;
}
}
x=1;
y=1;
MOVETO(16,2);
printf("2-down,8-up,4-left,6-right,5-insert,1-end");
int letra;
do
{
letra=getchar();
switch (letra){
case 2:
if (y<fil)
{
MOVELEFT(1);
printf("%d",matriz[y-1][(x/4)]);
y=y+1;
}
break;
case 8:
if (y>1)
{
MOVELEFT(1);
printf("%d",matriz[y-1][(x/4)]);
y=y-1;
}
break;
case 4:
if (x>1)
{
MOVELEFT(1);
printf("%d",matriz[y-1][(x/4)]);
x=x-4;
}
break;
case 6:
if (x<((col-1)*4))
{
MOVELEFT(1);
printf("%d",matriz[y-1][(x/4)]);
x=x+4;
}
break;
case 5:
MOVELEFT(1);
printf(" ");
MOVELEFT(4);
scanf("%d",&B);
matriz[y-1][(x/4)]=B;
break;
case 1:
MOVETO(20,10);
printf("If you want to end the modification enter f-end\n");
scanf("%s",letras);
break;
}
MOVETO(15,2);
printf ("value of row %d and column %d is %d \n",y,(x/4)+1,matriz[y-1][(x/4)]);
MOVETO(y,x);
printf("%d",B);
}while(letras!='f');
MOVELEFT(1);
printf(" ");
MOVELEFT(3);
printf("%d",matriz[y-1][(x/4)]);
MOVETO(17,2);
printf("END OF THE MODIFICATION\n");
}
int main(int argc, char **argv)
{
static int matriz[10][10];
int B;
static int fil,col;
register int i,j;
char caracter;
printf (" Enter the number of columns.\n");
scanf("%d", &col);
CLEAR();
printf("Now, enter the square matrix...\n");
sleep(1);
CLEAR();
fil=col;
for (i=0;i<fil;++i) {
for (j=0;j<col;++j) {
MOVETO(2,5);
printf (" Enter the value for the row %d and the column %d.\n",i+1,j+1);
MOVETO(4,5);
printf(" ");
MOVELEFT(6);
HIGHT_LIGHT();
scanf("%d", &B);
matriz[i][j]=B;
MOVETO(i*2+6,j*6+6);
UN_HIGHT_LIGHT();
printf("%d",B);
}
}
printf("\n");
sleep (1);
MOVETO(16,2);
printf(" Do you want to modify the matrix, s-yes/n-no\n");
scanf("%s",&caracter);
if (caracter=='s')
{
modificacion(matriz,fil,col);
}
printf("End of the program");
printf("Press any key\n");
caracter=getchar();
CLEAR();
return 0;
}